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 hw/xfree86/common/xf86platformBus.c |   10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

New commits:
commit 42aaf37241fedfd6a0f72b255f2d45d6ea34d8c6
Author: Zoltán Böszörményi <zboszor at gmail.com>
Date:   Wed Feb 12 21:29:52 2020 +0000

    Fix modesetting device matching through kmsdev device path
    
    xf86platformProbeDev didn't check the device path, fix it.
    
    This is a problem when trying to set up a non-PCI device via
    explicit xorg.conf.d configuration.
    
    An USB DisplayLink device, being non-PCI was always set up
    as a GPU device assigned to screen 0 instead of a regular
    framebuffer, potentially having its own dedicated screen,
    despite such configuration as below. Only the relevant parts
    of the configuration are quoted, it's part of a larger context
    with an Intel chip that has 3 outputs:
    * DP1 connected to an LCD panel,
    * VGA1 connected to an external monitor,
    * HDMI1 unconnected and having no user visible connector
    
    Section "ServerFlags"
            Option          "AutoBindGPU" "false"
    EndSection
    
    ...
    
    Section "Device"
            Identifier      "Intel2"
            Driver          "intel"
            BusID           "PCI:0:2:0"
            Screen          2
            Option          "Monitor-HDMI1" "HDMI1"
            Option          "ZaphodHeads" "HDMI1"
    EndSection
    
    Section "Device"
            Identifier      "UDL"
            Driver          "modesetting"
            Option          "kmsdev" "/dev/dri/card0"
            #BusID          "usb:0:1.2:1.0"
            Option          "Monitor-DVI-I-1" "DVI-I-1"
            Option          "ShadowFB" "on"
            Option          "DoubleShadow" "on"
    EndSection
    
    ...
    
    Section "Screen"
            Identifier      "SCREEN2"
            Option          "AutoServerLayout" "on"
            Device          "UDL"
            GPUDevice       "Intel2"
            Monitor         "Monitor-DVI-I-1"
            SubSection      "Display"
                    Modes   "1024x768"
                    Depth   24
            EndSubSection
    EndSection
    
    Section "ServerLayout"
            Identifier      "LAYOUT"
            Option          "AutoServerLayout" "on"
            Screen          0 "SCREEN"
            Screen          1 "SCREEN1" RightOf "SCREEN"
            Screen          2 "SCREEN2" RightOf "SCREEN1"
    EndSection
    
    On the particular machine I was trying to set up an UDL device,
    I found the following structure was being used to match
    the device to a platform device while I was debugging the issue:
    
    xf86_platform_devices[0] == Intel, /dev/dri/card1, primary platform device
    xf86_platform_devices[1] == UDL, /dev/dri/card0
    
    devList[0] == "Intel0", ZaphodHeads: DP1
    devList[1] == "Intel1", ZaphodHeads: VGA1
    devList[2] == "UDL"
    devList[3] == "Intel2", ZaphodHeads: HDMI1 (intended GPU device to UDL)
    
    When xf86platformProbeDev() matched the UDL device, the BusID
    check failed in both cases of:
    * BusID "usb:0:1.2:1.0" was specified
    * Option "kmsdev" "/dev/dri/card0" was specified
    
    As a result, xf86platformProbeDev() went on to call probeSingleDevice()
    with xf86_platform_devices[0] and devList[2], resulting in the
    UDL device being set up as a GPU device assigned to the first screen
    instead of as a framebuffer on the third screen as the configuration
    specified.
    
    Checking Option "kmsdev" in code code may be a layering violation.
    But the modesetting driver is actually part of the Xorg sources
    instead of being an external driver, so he "kmsdev" path knowledge
    may be used here.
    
    Signed-off-by: Böszörményi Zoltán <zboszor at pr.hu>

diff --git a/hw/xfree86/common/xf86platformBus.c b/hw/xfree86/common/xf86platformBus.c
index 23dffc9d6..f87760b63 100644
--- a/hw/xfree86/common/xf86platformBus.c
+++ b/hw/xfree86/common/xf86platformBus.c
@@ -536,12 +536,20 @@ xf86platformProbeDev(DriverPtr drvp)
 
     /* find the main device or any device specificed in xorg.conf */
     for (i = 0; i < numDevs; i++) {
+        const char *devpath;
+
         /* skip inactive devices */
         if (!devList[i]->active)
             continue;
 
+        /* This is specific to modesetting. */
+        devpath = xf86FindOptionValue(devList[i]->options, "kmsdev");
+
         for (j = 0; j < xf86_num_platform_devices; j++) {
-            if (devList[i]->busID && *devList[i]->busID) {
+            if (devpath && *devpath) {
+                if (strcmp(xf86_platform_devices[j].attribs->path, devpath) == 0)
+                    break;
+            } else if (devList[i]->busID && *devList[i]->busID) {
                 if (xf86PlatformDeviceCheckBusID(&xf86_platform_devices[j], devList[i]->busID))
                     break;
             }