[PATCH 2/7] xfree86: use udev to provide device enumeration for kms devices (v10)

Dave Airlie airlied at gmail.com
Mon Jun 25 03:58:37 PDT 2012


From: Dave Airlie <airlied at redhat.com>

On Linux in order for future hotplug work, we are required to interface
to udev to detect device creation/removal. In order to try and get
some earlier testing on this, this patch adds the ability to use
udev for device enumeration on Linux.

At startup the list of drm/kms devices is probed and this info is
used to load drivers.

A new driver probing method is introduced that passes the udev
device info to the driver for probing.

The probing integrates with the pci probing code and will fallback
to the pci probe and old school probe functions in turn.

The flags parameter to the probe function will be used later
to provide hotplug and gpu screen flags for the driver to behave
in a different way.

This patch changes the driver ABI, all drivers should at least
be set with a NULL udev probe function after this commit.

v2: rename to platform bus, now with 100% less udev specific,

this version passes config_odev_attribs around which are an array
of id/string pairs, then the udev code can attach the set of attribs
it understands, the OS specific code can attach its attrib, and then
the core/drivers can lookup the required attribs.

also add MATCH_PCI_DEVICES macro.

This version is mainly to address concerns raised by ajax.

v3: Address comments from Peter.
fix whitespace that snuck in.
rework to use a linked list with some core functions that
xf86 wraps.

v4: add free list, fix struct whitespace.
ajax this address most of your issues?

v5: drop probe ifdef, fix logic issue
v5 was Reviewed-by: Peter Hutterer <peter.hutterer at who-t.net>

v6: some overhaul after more testing.

Implement primaryBus for platform devices.
document hotplug.h dev attribs - drop sysname attrib
fix build with udev kms disabled
make probing work like the PCI probe code,
   match against bus id if one exists, or primary device.

RFC: add new bus id support "PLAT:syspath". we probably
want to match on this a bit different, or use a different
property maybe. I was mainly wanting this for use with
specifying usb devices in xorg.conf directly, but PLAT:path
could also work I suppose.

v6.1: add missing noop platform function

v7: fix two interactions with pci probing and slot claiming, prevents
pci and platform trying to load two drivers for same slot.

v8: test with zaphod mode on -ati driver, fixup resulting issue
clean up common probe code into another function, change busid
matching to allow dropping end of strings.

v9: fix platform probing logic so it actually works.
v9.1: fix pdev init to NULL properly.

v10: address most of Keith's concerns.

Signed-off-by: Dave Airlie <airlied at redhat.com>
---
 config/config-backends.h                     |    1 +
 config/config.c                              |   56 ++++
 config/udev.c                                |   69 +++++
 configure.ac                                 |   20 +-
 hw/xfree86/common/Makefile.am                |    8 +-
 hw/xfree86/common/xf86.h                     |    5 +
 hw/xfree86/common/xf86AutoConfig.c           |    9 +-
 hw/xfree86/common/xf86Bus.c                  |   18 +-
 hw/xfree86/common/xf86Bus.h                  |    1 +
 hw/xfree86/common/xf86fbBus.c                |    4 +
 hw/xfree86/common/xf86pciBus.c               |   41 ++-
 hw/xfree86/common/xf86pciBus.h               |   10 +
 hw/xfree86/common/xf86platformBus.c          |  379 ++++++++++++++++++++++++++
 hw/xfree86/common/xf86platformBus.h          |   59 ++++
 hw/xfree86/common/xf86str.h                  |   11 +
 hw/xfree86/os-support/linux/Makefile.am      |    2 +-
 hw/xfree86/os-support/linux/lnx_platform.c   |  130 +++++++++
 hw/xfree86/os-support/shared/platform_noop.c |   23 ++
 hw/xfree86/os-support/xf86_OSproc.h          |    6 +
 include/dix-config.h.in                      |    3 +
 include/hotplug.h                            |   35 +++
 include/xorg-config.h.in                     |    3 +
 include/xorg-server.h.in                     |    3 +
 23 files changed, 877 insertions(+), 19 deletions(-)
 create mode 100644 hw/xfree86/common/xf86platformBus.c
 create mode 100644 hw/xfree86/common/xf86platformBus.h
 create mode 100644 hw/xfree86/os-support/linux/lnx_platform.c
 create mode 100644 hw/xfree86/os-support/shared/platform_noop.c

diff --git a/config/config-backends.h b/config/config-backends.h
index 62abc0a..6423701 100644
--- a/config/config-backends.h
+++ b/config/config-backends.h
@@ -36,6 +36,7 @@ BOOL device_is_duplicate(const char *config_info);
 int config_udev_pre_init(void);
 int config_udev_init(void);
 void config_udev_fini(void);
+void config_udev_odev_probe(config_odev_probe_proc_ptr probe_callback);
 #else
 
 #ifdef CONFIG_NEED_DBUS
diff --git a/config/config.c b/config/config.c
index 24e7ba7..d0889a3 100644
--- a/config/config.c
+++ b/config/config.c
@@ -85,6 +85,14 @@ config_fini(void)
 #endif
 }
 
+void
+config_odev_probe(config_odev_probe_proc_ptr probe_callback)
+{
+#if defined(CONFIG_UDEV_KMS)
+    config_udev_odev_probe(probe_callback);
+#endif
+}
+
 static void
 remove_device(const char *backend, DeviceIntPtr dev)
 {
@@ -133,3 +141,51 @@ device_is_duplicate(const char *config_info)
 
     return FALSE;
 }
+
+struct OdevAttributes *
+config_odev_allocate_attribute_list(void)
+{
+    struct OdevAttributes *attriblist;
+
+    attriblist = malloc(sizeof(struct OdevAttributes));
+    if (!attriblist)
+        return NULL;
+
+    xorg_list_init(&attriblist->list);
+    return attriblist;
+}
+
+void
+config_odev_free_attribute_list(struct OdevAttributes *attribs)
+{
+    config_odev_free_attributes(attribs);
+    free(attribs);
+}
+
+Bool
+config_odev_add_attribute(struct OdevAttributes *attribs, int attrib,
+                          const char *attrib_name)
+{
+    struct OdevAttribute *oa;
+
+    oa = malloc(sizeof(struct OdevAttribute));
+    if (!oa)
+        return FALSE;
+
+    oa->attrib_id = attrib;
+    oa->attrib_name = strdup(attrib_name);
+    xorg_list_append(&oa->member, &attribs->list);
+    return TRUE;
+}
+
+void
+config_odev_free_attributes(struct OdevAttributes *attribs)
+{
+    struct OdevAttribute *iter, *safe;
+
+    xorg_list_for_each_entry_safe(iter, safe, &attribs->list, member) {
+        xorg_list_del(&iter->member);
+        free(iter->attrib_name);
+        free(iter);
+    }
+}
diff --git a/config/udev.c b/config/udev.c
index 1995184..efa8d32 100644
--- a/config/udev.c
+++ b/config/udev.c
@@ -366,3 +366,72 @@ config_udev_fini(void)
     udev_monitor = NULL;
     udev_unref(udev);
 }
+
+#ifdef CONFIG_UDEV_KMS
+
+static Bool
+config_udev_odev_setup_attribs(const char *path, const char *syspath,
+                               config_odev_probe_proc_ptr probe_callback)
+{
+    struct OdevAttributes *attribs = config_odev_allocate_attribute_list();
+    int ret;
+
+    if (!attribs)
+        return FALSE;
+
+    ret = config_odev_add_attribute(attribs, ODEV_ATTRIB_PATH, path);
+    if (ret == FALSE)
+        goto fail;
+
+    ret = config_odev_add_attribute(attribs, ODEV_ATTRIB_SYSPATH, syspath);
+    if (ret == FALSE)
+        goto fail;
+
+    /* ownership of attribs is passed to probe layer */
+    probe_callback(attribs);
+    return TRUE;
+fail:
+    config_odev_free_attributes(attribs);
+    free(attribs);
+    return FALSE;
+}
+
+void
+config_udev_odev_probe(config_odev_probe_proc_ptr probe_callback)
+{
+    struct udev *udev;
+    struct udev_enumerate *enumerate;
+    struct udev_list_entry *devices, *device;
+
+    udev = udev_monitor_get_udev(udev_monitor);
+    enumerate = udev_enumerate_new(udev);
+    if (!enumerate)
+        return;
+
+    udev_enumerate_add_match_subsystem(enumerate, "drm");
+    udev_enumerate_add_match_sysname(enumerate, "card[0-9]*");
+    udev_enumerate_scan_devices(enumerate);
+    devices = udev_enumerate_get_list_entry(enumerate);
+    udev_list_entry_foreach(device, devices) {
+        const char *syspath = udev_list_entry_get_name(device);
+        struct udev_device *udev_device = udev_device_new_from_syspath(udev, syspath);
+        const char *path = udev_device_get_devnode(udev_device);
+        const char *sysname = udev_device_get_sysname(udev_device);
+
+        if (!path || !syspath)
+            goto no_probe;
+        else if (strcmp(udev_device_get_subsystem(udev_device), "drm") != 0)
+            goto no_probe;
+        else if (strncmp(sysname, "card", 4) != 0)
+            goto no_probe;
+
+        config_udev_odev_setup_attribs(path, syspath, probe_callback);
+
+    no_probe:
+        udev_device_unref(udev_device);
+    }
+    udev_enumerate_unref(enumerate);
+    return;
+}
+#endif
+
diff --git a/configure.ac b/configure.ac
index 9ae77fb..b321e12 100644
--- a/configure.ac
+++ b/configure.ac
@@ -615,6 +615,7 @@ AC_ARG_ENABLE(dbe,            AS_HELP_STRING([--disable-dbe], [Build DBE extensi
 AC_ARG_ENABLE(xf86bigfont,    AS_HELP_STRING([--enable-xf86bigfont], [Build XF86 Big Font extension (default: disabled)]), [XF86BIGFONT=$enableval], [XF86BIGFONT=no])
 AC_ARG_ENABLE(dpms,           AS_HELP_STRING([--disable-dpms], [Build DPMS extension (default: enabled)]), [DPMSExtension=$enableval], [DPMSExtension=yes])
 AC_ARG_ENABLE(config-udev,    AS_HELP_STRING([--enable-config-udev], [Build udev support (default: auto)]), [CONFIG_UDEV=$enableval], [CONFIG_UDEV=auto])
+AC_ARG_ENABLE(config-udev-kms,    AS_HELP_STRING([--enable-config-udev-kms], [Build udev kms support (default: auto)]), [CONFIG_UDEV_KMS=$enableval], [CONFIG_UDEV_KMS=auto])
 AC_ARG_ENABLE(config-dbus,    AS_HELP_STRING([--enable-config-dbus], [Build D-BUS API support (default: no)]), [CONFIG_DBUS_API=$enableval], [CONFIG_DBUS_API=no])
 AC_ARG_ENABLE(config-hal,     AS_HELP_STRING([--disable-config-hal], [Build HAL support (default: auto)]), [CONFIG_HAL=$enableval], [CONFIG_HAL=auto])
 AC_ARG_ENABLE(config-wscons,  AS_HELP_STRING([--enable-config-wscons], [Build wscons config support (default: auto)]), [CONFIG_WSCONS=$enableval], [CONFIG_WSCONS=auto])
@@ -704,6 +705,7 @@ case $host_os in
 		CONFIG_DBUS_API=no
 		CONFIG_HAL=no
 		CONFIG_UDEV=no
+		CONFIG_UDEV_KMS=no
 		DGA=no
 		DRI2=no
 		INT10MODULE=no
@@ -838,11 +840,16 @@ AM_CONDITIONAL(CONFIG_UDEV, [test "x$CONFIG_UDEV" = xyes])
 if test "x$CONFIG_UDEV" = xyes; then
 	CONFIG_DBUS_API=no
 	CONFIG_HAL=no
+	if test "x$CONFIG_UDEV_KMS" = xauto; then
+		CONFIG_UDEV_KMS="$HAVE_LIBUDEV"
+	fi
 	if ! test "x$HAVE_LIBUDEV" = xyes; then
 		AC_MSG_ERROR([udev configuration API requested, but libudev is not installed])
 	fi
 	AC_DEFINE(CONFIG_UDEV, 1, [Use libudev for input hotplug])
-
+	if test "x$CONFIG_UDEV_KMS" = xyes; then
+		AC_DEFINE(CONFIG_UDEV_KMS, 1, [Use libudev for kms enumeration])
+	fi
 	SAVE_LIBS=$LIBS
 	SAVE_CFLAGS=$CFLAGS
 	CFLAGS=$UDEV_CFLAGS
@@ -852,6 +859,7 @@ if test "x$CONFIG_UDEV" = xyes; then
 	LIBS=$SAVE_LIBS
 	CFLAGS=$SAVE_CFLAGS
 fi
+AM_CONDITIONAL(CONFIG_UDEV_KMS, [test "x$CONFIG_UDEV_KMS" = xyes])
 
 dnl HAVE_DBUS is true if we actually have the D-Bus library, whereas
 dnl CONFIG_DBUS_API is true if we want to enable the D-Bus config
@@ -1099,7 +1107,7 @@ case "$DRI2,$HAVE_DRI2PROTO" in
 esac
 AM_CONDITIONAL(DRI2, test "x$DRI2" = xyes)
 
-if test "x$DRI" = xyes || test "x$DRI2" = xyes; then
+if test "x$DRI" = xyes || test "x$DRI2" = xyes || test "x$CONFIG_UDEV_KMS" = xyes; then
 	if test "x$DRM" = xyes; then
 		AC_DEFINE(WITH_LIBDRM, 1, [Building with libdrm support])
 		PKG_CHECK_MODULES([LIBDRM], $LIBDRM)
@@ -1630,7 +1638,7 @@ if test "x$XORG" = xyes; then
 
 	PKG_CHECK_MODULES([PCIACCESS], $LIBPCIACCESS)
 	SDK_REQUIRED_MODULES="$SDK_REQUIRED_MODULES $LIBPCIACCESS"
-	XORG_SYS_LIBS="$XORG_SYS_LIBS $PCIACCESS_LIBS $GLX_SYS_LIBS"
+	XORG_SYS_LIBS="$XORG_SYS_LIBS $PCIACCESS_LIBS $GLX_SYS_LIBS $LIBDRM_LIBS"
 	XORG_CFLAGS="$XORG_CFLAGS $PCIACCESS_CFLAGS"
 
 	AC_DEFINE(XSERVER_LIBPCIACCESS, 1, [Use libpciaccess for all pci manipulation])
@@ -1648,6 +1656,10 @@ if test "x$XORG" = xyes; then
 	fi
 	AC_MSG_RESULT([$PCI])
 
+	if test "x$CONFIG_UDEV_KMS" = xyes; then
+		AC_DEFINE(XSERVER_PLATFORM_BUS, 1, [X server supports platform device enumeration])
+	fi
+	AC_MSG_RESULT([$XSERVER_PLATFORM_BUS])
 	dnl ===================================================================
 	dnl ==================== end of PCI configuration =====================
 	dnl ===================================================================
@@ -1836,7 +1848,7 @@ AM_CONDITIONAL([SOLARIS_ASM_INLINE], [test "x$solaris_asm_inline" = xyes])
 AM_CONDITIONAL([SOLARIS_VT], [test "x$solaris_vt" = xyes])
 AM_CONDITIONAL([DGA], [test "x$DGA" = xyes])
 AM_CONDITIONAL([XF86VIDMODE], [test "x$XF86VIDMODE" = xyes])
-
+AM_CONDITIONAL([XORG_BUS_PLATFORM], [test "x$CONFIG_UDEV_KMS" = xyes])
 dnl XWin DDX
 
 AC_MSG_CHECKING([whether to build XWin DDX])
diff --git a/hw/xfree86/common/Makefile.am b/hw/xfree86/common/Makefile.am
index 2792177..65d98e6 100644
--- a/hw/xfree86/common/Makefile.am
+++ b/hw/xfree86/common/Makefile.am
@@ -22,9 +22,13 @@ if DGA
 DGASOURCES = xf86DGA.c
 endif
 
+if XORG_BUS_PLATFORM
+PLATSOURCES = xf86platformBus.c
+endif
+
 RANDRSOURCES = xf86RandR.c
 
-BUSSOURCES = xf86fbBus.c xf86noBus.c $(PCI_SOURCES) $(SBUS_SOURCES)
+BUSSOURCES = xf86fbBus.c xf86noBus.c $(PCI_SOURCES) $(SBUS_SOURCES) $(PLATSOURCES)
 
 MODEDEFSOURCES = $(srcdir)/vesamodes $(srcdir)/extramodes
 
@@ -56,7 +60,7 @@ sdk_HEADERS = compiler.h fourcc.h xf86.h xf86Module.h xf86Opt.h \
               xf86PciInfo.h xf86Priv.h xf86Privstr.h \
               xf86cmap.h xf86fbman.h xf86str.h xf86Xinput.h xisb.h \
               $(XVSDKINCS) $(XF86VMODE_SDK) xorgVersion.h \
-              xf86sbusBus.h xf86VGAarbiter.h xf86Optionstr.h
+              xf86sbusBus.h xf86VGAarbiter.h xf86Optionstr.h xf86platformBus.h
 
 DISTCLEANFILES = xf86Build.h
 CLEANFILES = $(BUILT_SOURCES)
diff --git a/hw/xfree86/common/xf86.h b/hw/xfree86/common/xf86.h
index 129660d..88a219c 100644
--- a/hw/xfree86/common/xf86.h
+++ b/hw/xfree86/common/xf86.h
@@ -71,6 +71,11 @@ extern _X_EXPORT Bool fbSlotClaimed;
 #if (defined(__sparc__) || defined(__sparc)) && !defined(__OpenBSD__)
 extern _X_EXPORT Bool sbusSlotClaimed;
 #endif
+
+#if defined(XSERVER_PLATFORM_BUS)
+extern _X_EXPORT int platformSlotClaimed;
+#endif
+
 extern _X_EXPORT confDRIRec xf86ConfigDRI;
 extern _X_EXPORT Bool xf86DRI2Enabled(void);
 
diff --git a/hw/xfree86/common/xf86AutoConfig.c b/hw/xfree86/common/xf86AutoConfig.c
index d0eb0af..271ce86 100644
--- a/hw/xfree86/common/xf86AutoConfig.c
+++ b/hw/xfree86/common/xf86AutoConfig.c
@@ -198,10 +198,13 @@ listPossibleVideoDrivers(char *matches[], int nmatches)
     }
     i = 0;
 
+#ifdef XSERVER_PLATFORM_BUS
+    i = xf86PlatformMatchDriver(matches, nmatches);
+#endif
 #ifdef sun
     /* Check for driver type based on /dev/fb type and if valid, use
        it instead of PCI bus probe results */
-    if (xf86Info.consoleFd >= 0) {
+    if (xf86Info.consoleFd >= 0 && (i < (nmatches - 1))) {
         struct vis_identifier visid;
         const char *cp;
         extern char xf86SolarisFbDev[PATH_MAX];
@@ -251,6 +254,7 @@ listPossibleVideoDrivers(char *matches[], int nmatches)
     }
 #endif
 #ifdef __sparc__
+    if (i < (nmatches - 1))
     {
         char *sbusDriver = sparcDriverName();
 
@@ -259,7 +263,8 @@ listPossibleVideoDrivers(char *matches[], int nmatches)
     }
 #endif
 #ifdef XSERVER_LIBPCIACCESS
-    i = xf86PciMatchDriver(matches, nmatches);
+    if (i < (nmatches - 1))
+        i = xf86PciMatchDriver(matches, nmatches);
 #endif
     /* Fallback to platform default hardware */
     if (i < (nmatches - 1)) {
diff --git a/hw/xfree86/common/xf86Bus.c b/hw/xfree86/common/xf86Bus.c
index 6c86f5e..d0cfb2b 100644
--- a/hw/xfree86/common/xf86Bus.c
+++ b/hw/xfree86/common/xf86Bus.c
@@ -77,8 +77,14 @@ xf86CallDriverProbe(DriverPtr drv, Bool detect_only)
 {
     Bool foundScreen = FALSE;
 
+#ifdef XSERVER_PLATFORM_BUS
+    if (drv->platformProbe != NULL) {
+        foundScreen = xf86platformProbeDev(drv);
+    }
+#endif
+
 #ifdef XSERVER_LIBPCIACCESS
-    if (drv->PciProbe != NULL) {
+    if (!foundScreen && (drv->PciProbe != NULL)) {
         if (xf86DoConfigure && xf86DoConfigurePass1) {
             assert(detect_only);
             foundScreen = xf86PciAddMatchingDev(drv);
@@ -202,6 +208,9 @@ xf86BusConfig(void)
 void
 xf86BusProbe(void)
 {
+#ifdef XSERVER_PLATFORM_BUS
+    xf86platformProbe();
+#endif
 #ifdef XSERVER_LIBPCIACCESS
     xf86PciProbe();
 #endif
@@ -238,6 +247,8 @@ StringToBusType(const char *busID, const char **retID)
         ret = BUS_PCI;
     if (!xf86NameCmp(p, "sbus"))
         ret = BUS_SBUS;
+    if (!xf86NameCmp(p, "platform"))
+        ret = BUS_PLATFORM;
     if (ret != BUS_NONE)
         if (retID)
             *retID = busID + strlen(p) + 1;
@@ -270,6 +281,8 @@ xf86IsEntityPrimary(int entityIndex)
         return pEnt->bus.id.pci == primaryBus.id.pci;
     case BUS_SBUS:
         return pEnt->bus.id.sbus.fbNum == primaryBus.id.sbus.fbNum;
+    case BUS_PLATFORM:
+        return pEnt->bus.id.plat == primaryBus.id.plat;
     default:
         return FALSE;
     }
@@ -541,6 +554,9 @@ xf86PostProbe(void)
 #if (defined(__sparc__) || defined(__sparc)) && !defined(__OpenBSD__)
                              sbusSlotClaimed ||
 #endif
+#ifdef XSERVER_PLATFORM_BUS
+                             platformSlotClaimed ||
+#endif
 #ifdef XSERVER_LIBPCIACCESS
                              pciSlotClaimed
 #else
diff --git a/hw/xfree86/common/xf86Bus.h b/hw/xfree86/common/xf86Bus.h
index abf2efd..e83ba78 100644
--- a/hw/xfree86/common/xf86Bus.h
+++ b/hw/xfree86/common/xf86Bus.h
@@ -42,6 +42,7 @@
 #if defined(__sparc__) || defined(__sparc)
 #include "xf86sbusBus.h"
 #endif
+#include "xf86platformBus.h"
 
 typedef struct {
     DriverPtr driver;
diff --git a/hw/xfree86/common/xf86fbBus.c b/hw/xfree86/common/xf86fbBus.c
index 1e51623..303b9c2 100644
--- a/hw/xfree86/common/xf86fbBus.c
+++ b/hw/xfree86/common/xf86fbBus.c
@@ -54,6 +54,10 @@ xf86ClaimFbSlot(DriverPtr drvp, int chipset, GDevPtr dev, Bool active)
     EntityPtr p;
     int num;
 
+#ifdef XSERVER_PLATFORM_BUS
+    if (platformSlotClaimed)
+        return -1;
+#endif
 #ifdef XSERVER_LIBPCIACCESS
     if (pciSlotClaimed)
         return -1;
diff --git a/hw/xfree86/common/xf86pciBus.c b/hw/xfree86/common/xf86pciBus.c
index d758260..a2c18eb 100644
--- a/hw/xfree86/common/xf86pciBus.c
+++ b/hw/xfree86/common/xf86pciBus.c
@@ -110,7 +110,7 @@ xf86PciProbe(void)
             xf86PciVideoInfo[num - 1] = info;
 
             pci_device_probe(info);
-            if (pci_device_is_boot_vga(info)) {
+            if (primaryBus.type == BUS_NONE && pci_device_is_boot_vga(info)) {
                 primaryBus.type = BUS_PCI;
                 primaryBus.id.pci = info;
             }
@@ -352,7 +352,15 @@ xf86ComparePciBusString(const char *busID, int bus, int device, int func)
 Bool
 xf86IsPrimaryPci(struct pci_device *pPci)
 {
-    return ((primaryBus.type == BUS_PCI) && (pPci == primaryBus.id.pci));
+    if (primaryBus.type == BUS_PCI)
+        return pPci == primaryBus.id.pci;
+#ifdef XSERVER_PLATFORM_BUS
+    if (primaryBus.type == BUS_PLATFORM)
+        if (primaryBus.id.plat->pdev)
+            if (MATCH_PCI_DEVICES(primaryBus.id.plat->pdev, pPci))
+                return TRUE;
+#endif
+    return FALSE;
 }
 
 /*
@@ -367,7 +375,15 @@ xf86GetPciInfoForEntity(int entityIndex)
         return NULL;
 
     p = xf86Entities[entityIndex];
-    return (p->bus.type == BUS_PCI) ? p->bus.id.pci : NULL;
+    switch (p->bus.type) {
+    case BUS_PCI:
+        return p->bus.id.pci;
+    case BUS_PLATFORM:
+        return p->bus.id.plat->pdev;
+    default:
+        break;
+    }
+    return NULL;
 }
 
 /*
@@ -400,6 +416,13 @@ xf86CheckPciSlot(const struct pci_device *d)
         if ((p->bus.type == BUS_PCI) && (p->bus.id.pci == d)) {
             return FALSE;
         }
+#ifdef XSERVER_PLATFORM_BUS
+        if ((p->bus.type == BUS_PLATFORM) && (p->bus.id.plat->pdev)) {
+            struct pci_device *ud = p->bus.id.plat->pdev;
+            if (MATCH_PCI_DEVICES(ud, d))
+                return FALSE;
+        }
+#endif
     }
     return TRUE;
 }
@@ -1065,8 +1088,8 @@ xf86ConfigActivePciEntity(ScrnInfoPtr pScrn, int entityIndex,
     return TRUE;
 }
 
-static int
-videoPtrToDriverList(struct pci_device *dev,
+int
+xf86VideoPtrToDriverList(struct pci_device *dev,
                      char *returnList[], int returnListMax)
 {
     int i;
@@ -1249,8 +1272,8 @@ xchomp(char *line)
  * don't export their PCI ID's properly. If distros don't end up using this
  * feature it can and should be removed because the symbol-based resolution
  * scheme should be the primary one */
-static void
-matchDriverFromFiles(char **matches, uint16_t match_vendor, uint16_t match_chip)
+void
+xf86MatchDriverFromFiles(char **matches, uint16_t match_vendor, uint16_t match_chip)
 {
     DIR *idsdir;
     FILE *fp;
@@ -1379,7 +1402,7 @@ xf86PciMatchDriver(char *matches[], int nmatches)
     pci_iterator_destroy(iter);
 #ifdef __linux__
     if (info)
-        matchDriverFromFiles(matches, info->vendor_id, info->device_id);
+        xf86MatchDriverFromFiles(matches, info->vendor_id, info->device_id);
 #endif
 
     for (i = 0; (i < nmatches) && (matches[i]); i++) {
@@ -1387,7 +1410,7 @@ xf86PciMatchDriver(char *matches[], int nmatches)
     }
 
     if ((info != NULL) && (i < nmatches)) {
-        i += videoPtrToDriverList(info, &(matches[i]), nmatches - i);
+        i += xf86VideoPtrToDriverList(info, &(matches[i]), nmatches - i);
     }
 
     return i;
diff --git a/hw/xfree86/common/xf86pciBus.h b/hw/xfree86/common/xf86pciBus.h
index 56ec6e9..4972c36 100644
--- a/hw/xfree86/common/xf86pciBus.h
+++ b/hw/xfree86/common/xf86pciBus.h
@@ -42,4 +42,14 @@ Bool xf86PciConfigure(void *busData, struct pci_device *pDev);
 void xf86PciConfigureNewDev(void *busData, struct pci_device *pVideo,
                             GDevRec * GDev, int *chipset);
 
+#define MATCH_PCI_DEVICES(x, y) (((x)->domain == (y)->domain) &&        \
+                                 ((x)->bus == (y)->bus) &&              \
+                                 ((x)->func == (y)->func) &&            \
+                                 ((x)->dev == (y)->dev))
+
+void
+xf86MatchDriverFromFiles(char **matches, uint16_t match_vendor, uint16_t match_chip);
+int
+xf86VideoPtrToDriverList(struct pci_device *dev,
+                         char *returnList[], int returnListMax);
 #endif                          /* _XF86_PCI_BUS_H */
diff --git a/hw/xfree86/common/xf86platformBus.c b/hw/xfree86/common/xf86platformBus.c
new file mode 100644
index 0000000..50b7636
--- /dev/null
+++ b/hw/xfree86/common/xf86platformBus.c
@@ -0,0 +1,379 @@
+/*
+ * Copyright © 2012 Red Hat.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+ * DEALINGS IN THE SOFTWARE.
+ *
+ * Author: Dave Airlie <airlied at redhat.com>
+ */
+
+/*
+ * This file contains the interfaces to the bus-specific code
+ */
+
+#ifdef HAVE_XORG_CONFIG_H
+#include <xorg-config.h>
+#endif
+
+#ifdef XSERVER_PLATFORM_BUS
+#include <errno.h>
+
+#include <pciaccess.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include "os.h"
+#include "hotplug.h"
+
+#include "xf86.h"
+#include "xf86_OSproc.h"
+#include "xf86Priv.h"
+#include "xf86str.h"
+#include "xf86Bus.h"
+#include "Pci.h"
+#include "xf86platformBus.h"
+
+int platformSlotClaimed;
+
+int xf86_num_platform_devices;
+
+static struct xf86_platform_device *xf86_platform_devices;
+
+int
+xf86_add_platform_device(struct OdevAttributes *attribs)
+{
+    xf86_platform_devices = xnfrealloc(xf86_platform_devices,
+                                   (sizeof(struct xf86_platform_device)
+                                    * (xf86_num_platform_devices + 1)));
+
+    xf86_platform_devices[xf86_num_platform_devices].attribs = attribs;
+    xf86_platform_devices[xf86_num_platform_devices].pdev = NULL;
+
+    xf86_num_platform_devices++;
+    return 0;
+}
+
+int
+xf86_remove_platform_device(int dev_index)
+{
+    int j;
+
+    config_odev_free_attribute_list(xf86_platform_devices[dev_index].attribs);
+
+    for (j = dev_index; j < xf86_num_platform_devices - 1; j++)
+        memcpy(&xf86_platform_devices[j], &xf86_platform_devices[j + 1], sizeof(struct xf86_platform_device));
+    xf86_num_platform_devices--;
+    return 0;
+}
+
+Bool
+xf86_add_platform_device_attrib(int index, int attrib_id, char *attrib_name)
+{
+    struct xf86_platform_device *device = &xf86_platform_devices[index];
+
+    return config_odev_add_attribute(device->attribs, attrib_id, attrib_name);
+}
+
+char *
+xf86_get_platform_attrib(int index, int attrib_id)
+{
+    struct xf86_platform_device *device = &xf86_platform_devices[index];
+    struct OdevAttribute *oa;
+
+    xorg_list_for_each_entry(oa, &device->attribs->list, member) {
+        if (oa->attrib_id == attrib_id)
+            return oa->attrib_name;
+    }
+    return NULL;
+}
+
+char *
+xf86_get_platform_device_attrib(struct xf86_platform_device *device, int attrib_id)
+{
+    struct OdevAttribute *oa;
+
+    xorg_list_for_each_entry(oa, &device->attribs->list, member) {
+        if (oa->attrib_id == attrib_id)
+            return oa->attrib_name;
+    }
+    return NULL;
+}
+
+
+/*
+ * xf86IsPrimaryPlatform() -- return TRUE if primary device
+ * is a platform device and it matches this one.
+ */
+
+static Bool
+xf86IsPrimaryPlatform(struct xf86_platform_device *plat)
+{
+    return ((primaryBus.type == BUS_PLATFORM) && (plat == primaryBus.id.plat));
+}
+
+static void
+platform_find_pci_info(struct xf86_platform_device *pd, char *busid)
+{
+    struct pci_slot_match devmatch;
+    struct pci_device *info;
+    struct pci_device_iterator *iter;
+    int ret;
+
+    ret = sscanf(busid, "pci:%04x:%02x:%02x.%u",
+                 &devmatch.domain, &devmatch.bus, &devmatch.dev,
+                 &devmatch.func);
+    if (ret != 4)
+        return;
+
+    iter = pci_slot_match_iterator_create(&devmatch);
+    info = pci_device_next(iter);
+    if (info) {
+        pd->pdev = info;
+        pci_device_probe(info);
+        if (pci_device_is_boot_vga(info)) {
+            primaryBus.type = BUS_PLATFORM;
+            primaryBus.id.plat = pd;
+        }
+    }
+    pci_iterator_destroy(iter);
+
+}
+
+static Bool
+xf86_check_platform_slot(const struct xf86_platform_device *pd)
+{
+    int i;
+
+    for (i = 0; i < xf86NumEntities; i++) {
+        const EntityPtr u = xf86Entities[i];
+
+        if (pd->pdev && u->bus.type == BUS_PCI)
+            return !MATCH_PCI_DEVICES(pd->pdev, u->bus.id.pci);
+        if ((u->bus.type == BUS_PLATFORM) && (pd == u->bus.id.plat)) {
+            return FALSE;
+        }
+    }
+    return TRUE;
+}
+
+/**
+ *  @return The numbers of found devices that match with the current system
+ *  drivers.
+ */
+int
+xf86PlatformMatchDriver(char *matches[], int nmatches)
+{
+    int i, j = 0;
+    struct pci_device *info = NULL;
+    int pass = 0;
+
+    for (pass = 0; pass < 2; pass++) {
+        for (i = 0; i < xf86_num_platform_devices; i++) {
+
+            if (xf86IsPrimaryPlatform(&xf86_platform_devices[i]) && (pass == 1))
+                continue;
+            else if (!xf86IsPrimaryPlatform(&xf86_platform_devices[i]) && (pass == 0))
+                continue;
+
+            info = xf86_platform_devices[i].pdev;
+#ifdef __linux__
+            if (info)
+                xf86MatchDriverFromFiles(matches, info->vendor_id, info->device_id);
+#endif
+
+            for (j = 0; (j < nmatches) && (matches[j]); j++) {
+                /* find end of matches list */
+            }
+
+            if ((info != NULL) && (j < nmatches)) {
+                j += xf86VideoPtrToDriverList(info, &(matches[j]), nmatches - j);
+            }
+        }
+    }
+    return j;
+}
+
+int
+xf86platformProbe(void)
+{
+    int i;
+    Bool pci = TRUE;
+
+    if (!xf86scanpci()) {
+        pci = FALSE;
+    }
+
+    config_odev_probe(&xf86PlatformDeviceProbe);
+    for (i = 0; i < xf86_num_platform_devices; i++) {
+        char *busid = xf86_get_platform_attrib(i, ODEV_ATTRIB_BUSID);
+
+        if (pci && (strncmp(busid, "pci:", 4) == 0)) {
+            platform_find_pci_info(&xf86_platform_devices[i], busid);
+        }
+    }
+    return 0;
+}
+
+static int
+xf86ClaimPlatformSlot(struct xf86_platform_device * d, DriverPtr drvp,
+                  int chipset, GDevPtr dev, Bool active)
+{
+    EntityPtr p = NULL;
+    int num;
+
+    if (xf86_check_platform_slot(d)) {
+        num = xf86AllocateEntity();
+        p = xf86Entities[num];
+        p->driver = drvp;
+        p->chipset = chipset;
+        p->bus.type = BUS_PLATFORM;
+        p->bus.id.plat = d;
+        p->active = active;
+        p->inUse = FALSE;
+        if (dev)
+            xf86AddDevToEntity(num, dev);
+
+        platformSlotClaimed++;
+        return num;
+    }
+    else
+        return -1;
+}
+
+static int
+xf86UnclaimPlatformSlot(struct xf86_platform_device *d, GDevPtr dev)
+{
+    int i;
+
+    for (i = 0; i < xf86NumEntities; i++) {
+        const EntityPtr p = xf86Entities[i];
+
+        if ((p->bus.type == BUS_PLATFORM) && (p->bus.id.plat == d)) {
+            if (dev)
+                xf86RemoveDevFromEntity(i, dev);
+            platformSlotClaimed--;
+            p->bus.type = BUS_NONE;
+            return 0;
+        }
+    }
+    return 0;
+}
+
+
+#define END_OF_MATCHES(m)                                               \
+    (((m).vendor_id == 0) && ((m).device_id == 0) && ((m).subvendor_id == 0))
+
+static Bool doPlatformProbe(struct xf86_platform_device *dev, DriverPtr drvp,
+                            GDevPtr gdev, int flags, intptr_t match_data)
+{
+    Bool foundScreen = FALSE;
+    int entity;
+
+    if (gdev->screen == 0 && !xf86_check_platform_slot(dev))
+        return FALSE;
+
+    entity = xf86ClaimPlatformSlot(dev, drvp, 0,
+                                   gdev, gdev->active);
+
+    if ((entity == -1) && (gdev->screen > 0)) {
+        unsigned nent;
+
+        for (nent = 0; nent < xf86NumEntities; nent++) {
+            EntityPtr pEnt = xf86Entities[nent];
+
+            if (pEnt->bus.type != BUS_PLATFORM)
+                continue;
+            if (pEnt->bus.id.plat == dev) {
+                entity = nent;
+                xf86AddDevToEntity(nent, gdev);
+                break;
+            }
+        }
+    }
+    if (entity != -1) {
+        if (drvp->platformProbe(drvp, entity, flags, dev, match_data))
+            foundScreen = TRUE;
+        else
+            xf86UnclaimPlatformSlot(dev, gdev);
+    }
+    return foundScreen;
+}
+
+static Bool
+probeSingleDevice(struct xf86_platform_device *dev, DriverPtr drvp, GDevPtr gdev, int flags)
+{
+    int k;
+    Bool foundScreen = FALSE;
+    struct pci_device *pPci;
+    const struct pci_id_match *const devices = drvp->supported_devices;
+
+    if (dev->pdev && devices) {
+        int device_id = dev->pdev->device_id;
+        pPci = dev->pdev;
+        for (k = 0; !END_OF_MATCHES(devices[k]); k++) {
+            if (PCI_ID_COMPARE(devices[k].vendor_id, pPci->vendor_id)
+                && PCI_ID_COMPARE(devices[k].device_id, device_id)
+                && ((devices[k].device_class_mask & pPci->device_class)
+                    ==  devices[k].device_class)) {
+                foundScreen = doPlatformProbe(dev, drvp, gdev, flags, devices[k].match_data);
+                if (foundScreen)
+                    break;
+            }
+        }
+    }
+    else if (dev->pdev && !devices)
+        return FALSE;
+    else
+        foundScreen = doPlatformProbe(dev, drvp, gdev, flags, 0);
+    return foundScreen;
+}
+
+int
+xf86platformProbeDev(DriverPtr drvp)
+{
+    Bool foundScreen = FALSE;
+    GDevPtr *devList;
+    const unsigned numDevs = xf86MatchDevice(drvp->driverName, &devList);
+    int i, j;
+
+    /* find the main device or any device specificed in xorg.conf */
+    for (i = 0; i < numDevs; i++) {
+        for (j = 0; j < xf86_num_platform_devices; j++) {
+            if (devList[i]->busID && *devList[i]->busID) {
+                if (xf86PlatformDeviceCheckBusID(&xf86_platform_devices[j], devList[i]->busID))
+                    break;
+            }
+            else {
+                if (xf86_platform_devices[j].pdev) {
+                    if (xf86IsPrimaryPlatform(&xf86_platform_devices[j]))
+                        break;
+                }
+            }
+        }
+
+        if (j == xf86_num_platform_devices)
+             continue;
+
+        foundScreen = probeSingleDevice(&xf86_platform_devices[j], drvp, devList[i], 0);
+        if (!foundScreen)
+            continue;
+    }
+
+    return foundScreen;
+}
+
+#endif
diff --git a/hw/xfree86/common/xf86platformBus.h b/hw/xfree86/common/xf86platformBus.h
new file mode 100644
index 0000000..15a3022
--- /dev/null
+++ b/hw/xfree86/common/xf86platformBus.h
@@ -0,0 +1,59 @@
+/*
+ * Copyright © 2012 Red Hat.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+ * DEALINGS IN THE SOFTWARE.
+ *
+ * Author: Dave Airlie <airlied at redhat.com>
+ */
+#ifndef XF86_PLATFORM_BUS_H
+#define XF86_PLATFORM_BUS_H
+
+#include "hotplug.h"
+
+struct xf86_platform_device {
+    struct OdevAttributes *attribs;
+    /* for PCI devices */
+    struct pci_device *pdev;
+};
+
+#ifdef XSERVER_PLATFORM_BUS
+int xf86platformProbe(void);
+int xf86platformProbeDev(DriverPtr drvp);
+
+extern int xf86_num_platform_devices;
+
+extern char *
+xf86_get_platform_attrib(int index, int attrib_id);
+extern int
+xf86_add_platform_device(struct OdevAttributes *attribs);
+extern int
+xf86_remove_platform_device(int dev_index);
+extern Bool
+xf86_add_platform_device_attrib(int index, int attrib_id, char *attrib_str);
+
+extern _X_EXPORT char *
+xf86_get_platform_device_attrib(struct xf86_platform_device *device, int attrib_id);
+extern _X_EXPORT Bool
+xf86PlatformDeviceCheckBusID(struct xf86_platform_device *device, const char *busid);
+
+extern _X_EXPORT int
+xf86PlatformMatchDriver(char *matches[], int nmatches);
+#endif
+
+#endif
diff --git a/hw/xfree86/common/xf86str.h b/hw/xfree86/common/xf86str.h
index a1404c3..e12dcc4 100644
--- a/hw/xfree86/common/xf86str.h
+++ b/hw/xfree86/common/xf86str.h
@@ -311,6 +311,7 @@ struct _SymTabRec;
 struct _PciChipsets;
 
 struct pci_device;
+struct xf86_platform_device;
 
 typedef struct _DriverRec {
     int driverVersion;
@@ -325,9 +326,16 @@ typedef struct _DriverRec {
     const struct pci_id_match *supported_devices;
     Bool (*PciProbe) (struct _DriverRec * drv, int entity_num,
                       struct pci_device * dev, intptr_t match_data);
+    Bool (*platformProbe) (struct _DriverRec * drv, int entity_num, int flags,
+                           struct xf86_platform_device * dev, intptr_t match_data);
 } DriverRec, *DriverPtr;
 
 /*
+ * platform probe flags
+ * no flags are defined yet - but drivers should fail to load if a flag they
+ * don't understand is passed.
+ */
+/*
  *  AddDriver flags
  */
 #define HaveDriverFuncs 1
@@ -343,6 +351,7 @@ typedef struct _DriverRec {
 #undef BUS_NONE
 #undef BUS_PCI
 #undef BUS_SBUS
+#undef BUS_PLATFORM
 #undef BUS_last
 #endif
 
@@ -350,6 +359,7 @@ typedef enum {
     BUS_NONE,
     BUS_PCI,
     BUS_SBUS,
+    BUS_PLATFORM,
     BUS_last                    /* Keep last */
 } BusType;
 
@@ -362,6 +372,7 @@ typedef struct _bus {
     union {
         struct pci_device *pci;
         SbusBusId sbus;
+        struct xf86_platform_device *plat;
     } id;
 } BusRec, *BusPtr;
 
diff --git a/hw/xfree86/os-support/linux/Makefile.am b/hw/xfree86/os-support/linux/Makefile.am
index 36748df..61175b3 100644
--- a/hw/xfree86/os-support/linux/Makefile.am
+++ b/hw/xfree86/os-support/linux/Makefile.am
@@ -22,7 +22,7 @@ XORG_CFLAGS += -DHAVE_APM
 endif
 
 liblinux_la_SOURCES = lnx_init.c lnx_video.c \
-                     lnx_agp.c lnx_kmod.c lnx_bell.c \
+                     lnx_agp.c lnx_kmod.c lnx_bell.c lnx_platform.c \
                      $(srcdir)/../shared/bios_mmap.c \
 		     $(srcdir)/../shared/VTsw_usl.c \
 		     $(srcdir)/../shared/posix_tty.c \
diff --git a/hw/xfree86/os-support/linux/lnx_platform.c b/hw/xfree86/os-support/linux/lnx_platform.c
new file mode 100644
index 0000000..9c63ee5
--- /dev/null
+++ b/hw/xfree86/os-support/linux/lnx_platform.c
@@ -0,0 +1,130 @@
+#ifdef HAVE_XORG_CONFIG_H
+#include <xorg-config.h>
+#endif
+
+#ifdef XSERVER_PLATFORM_BUS
+
+#include <xf86drm.h>
+#include <fcntl.h>
+#include <unistd.h>
+
+/* Linux platform device support */
+#include "xf86_OSproc.h"
+
+#include "xf86.h"
+#include "xf86platformBus.h"
+#include "xf86Bus.h"
+
+static Bool
+get_drm_info(struct OdevAttributes *attribs, char *path)
+{
+    drmSetVersion sv;
+    char *buf;
+    int fd;
+
+    fd = open(path, O_RDWR, O_CLOEXEC);
+    if (fd == -1)
+        return FALSE;
+
+    sv.drm_di_major = 1;
+    sv.drm_di_minor = 4;
+    sv.drm_dd_major = -1;       /* Don't care */
+    sv.drm_dd_minor = -1;       /* Don't care */
+    if (drmSetInterfaceVersion(fd, &sv)) {
+        ErrorF("setversion 1.4 failed\n");
+        return FALSE;
+    }
+
+    xf86_add_platform_device(attribs);
+
+    buf = drmGetBusid(fd);
+    xf86_add_platform_device_attrib(xf86_num_platform_devices - 1,
+                                    ODEV_ATTRIB_BUSID, buf);
+    drmFreeBusid(buf);
+    close(fd);
+    return TRUE;
+}
+
+Bool
+xf86PlatformDeviceCheckBusID(struct xf86_platform_device *device, const char *busid)
+{
+    struct OdevAttribute *attrib;
+    const char *syspath = NULL;
+    BusType bustype;
+    const char *id;
+    xorg_list_for_each_entry(attrib, &device->attribs->list, member) {
+        if (attrib->attrib_id == ODEV_ATTRIB_SYSPATH) {
+            syspath = attrib->attrib_name;
+            break;
+        }
+    }
+
+    if (!syspath)
+        return FALSE;
+
+    bustype = StringToBusType(busid, &id);
+    if (bustype == BUS_PCI) {
+        struct pci_device *pPci = device->pdev;
+        if (xf86ComparePciBusString(busid,
+                                    ((pPci->domain << 8)
+                                     | pPci->bus),
+                                    pPci->dev, pPci->func)) {
+            return TRUE;
+        }
+    }
+    else if (bustype == BUS_PLATFORM) {
+        /* match on the minimum string */
+        int len = strlen(id);
+
+        if (strlen(syspath) < strlen(id))
+            len = strlen(syspath);
+
+        if (strncmp(id, syspath, len))
+            return FALSE;
+        return TRUE;
+    }
+    return FALSE;
+}
+
+void
+xf86PlatformDeviceProbe(struct OdevAttributes *attribs)
+{
+    struct OdevAttribute *attrib;
+    int i;
+    char *path = NULL;
+    Bool ret;
+
+    xorg_list_for_each_entry(attrib, &attribs->list, member) {
+        if (attrib->attrib_id == ODEV_ATTRIB_PATH) {
+            path = attrib->attrib_name;
+            break;
+        }
+    }
+    if (!path)
+        goto out_free;
+
+    for (i = 0; i < xf86_num_platform_devices; i++) {
+        char *dpath;
+        dpath = xf86_get_platform_attrib(i, ODEV_ATTRIB_PATH);
+
+        if (!strcmp(path, dpath))
+            break;
+    }
+
+    if (i != xf86_num_platform_devices)
+        goto out_free;
+
+    LogMessage(X_INFO, "config/udev: Adding drm device (%s)\n",
+               path);
+
+    ret = get_drm_info(attribs, path);
+    if (ret == FALSE)
+        goto out_free;
+
+    return;
+
+out_free:
+    config_odev_free_attribute_list(attribs);
+}
+
+#endif
diff --git a/hw/xfree86/os-support/shared/platform_noop.c b/hw/xfree86/os-support/shared/platform_noop.c
new file mode 100644
index 0000000..199ae5e
--- /dev/null
+++ b/hw/xfree86/os-support/shared/platform_noop.c
@@ -0,0 +1,23 @@
+
+#ifdef HAVE_XORG_CONFIG_H
+#include <xorg-config.h>
+#endif
+
+#ifdef XSERVER_PLATFORM_BUS
+/* noop platform device support */
+#include "xf86_OSproc.h"
+
+#include "xf86.h"
+#include "xf86platformBus.h"
+
+Bool
+xf86PlatformDeviceCheckBusID(struct xf86_platform_device *device, const char *busid)
+{
+    return FALSE;
+}
+
+void xf86PlatformDeviceProbe(struct OdevAttributes *attribs)
+{
+
+}
+#endif
diff --git a/hw/xfree86/os-support/xf86_OSproc.h b/hw/xfree86/os-support/xf86_OSproc.h
index e171146..2f0172e 100644
--- a/hw/xfree86/os-support/xf86_OSproc.h
+++ b/hw/xfree86/os-support/xf86_OSproc.h
@@ -221,6 +221,12 @@ extern _X_EXPORT void xf86InitVidMem(void);
 
 #endif                          /* XF86_OS_PRIVS */
 
+#ifdef XSERVER_PLATFORM_BUS
+#include "hotplug.h"
+void
+xf86PlatformDeviceProbe(struct OdevAttributes *attribs);
+#endif
+
 _XFUNCPROTOEND
 #endif                          /* NO_OSLIB_PROTOTYPES */
 #endif                          /* _XF86_OSPROC_H */
diff --git a/include/dix-config.h.in b/include/dix-config.h.in
index 3c9bbaf..77681a9 100644
--- a/include/dix-config.h.in
+++ b/include/dix-config.h.in
@@ -390,6 +390,9 @@
 /* Use libudev for input hotplug */
 #undef CONFIG_UDEV
 
+/* Use libudev for kms enumeration */
+#undef CONFIG_UDEV_KMS
+
 /* Use udev_monitor_filter_add_match_tag() */
 #undef HAVE_UDEV_MONITOR_FILTER_ADD_MATCH_TAG
 
diff --git a/include/hotplug.h b/include/hotplug.h
index f3eeea2..5000762 100644
--- a/include/hotplug.h
+++ b/include/hotplug.h
@@ -26,8 +26,43 @@
 #ifndef HOTPLUG_H
 #define HOTPLUG_H
 
+#include "list.h"
+
 extern _X_EXPORT void config_pre_init(void);
 extern _X_EXPORT void config_init(void);
 extern _X_EXPORT void config_fini(void);
 
+struct OdevAttribute {
+    struct xorg_list member;
+    int attrib_id;
+    char *attrib_name;
+};
+
+struct OdevAttributes {
+    struct xorg_list list;
+};
+
+struct OdevAttributes *
+config_odev_allocate_attribute_list(void);
+
+void
+config_odev_free_attribute_list(struct OdevAttributes *attribs);
+
+Bool
+config_odev_add_attribute(struct OdevAttributes *attribs, int attrib,
+                          const char *attrib_name);
+
+void
+config_odev_free_attributes(struct OdevAttributes *attribs);
+
+/* path to kernel device node - Linux e.g. /dev/dri/card0 */
+#define ODEV_ATTRIB_PATH 1
+/* system device path - Linux e.g. /sys/devices/pci0000:00/0000:00:01.0/0000:01:00.0/drm/card1 */
+#define ODEV_ATTRIB_SYSPATH 2
+/* DRI-style bus id */
+#define ODEV_ATTRIB_BUSID 3
+
+typedef void (*config_odev_probe_proc_ptr)(struct OdevAttributes *attribs);
+void config_odev_probe(config_odev_probe_proc_ptr probe_callback);
+
 #endif                          /* HOTPLUG_H */
diff --git a/include/xorg-config.h.in b/include/xorg-config.h.in
index 2cc416a..a71b25d 100644
--- a/include/xorg-config.h.in
+++ b/include/xorg-config.h.in
@@ -136,4 +136,7 @@
 /* Have getresuid */
 #undef HAVE_GETRESUID
 
+/* Have X server platform bus support */
+#undef XSERVER_PLATFORM_BUS
+
 #endif /* _XORG_CONFIG_H_ */
diff --git a/include/xorg-server.h.in b/include/xorg-server.h.in
index 8086f32..c0761f7 100644
--- a/include/xorg-server.h.in
+++ b/include/xorg-server.h.in
@@ -205,6 +205,9 @@
 /* X Access Control Extension */
 #undef XACE
 
+/* Have X server platform bus support */
+#undef XSERVER_PLATFORM_BUS
+
 #ifdef _LP64
 #define _XSERVER64 1
 #endif
-- 
1.7.10.2



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