[PATCH] intel_display.c: make acpi_video last in backlight_interfaces

[Alon Levy]

On Sun, Aug 26, 2012 at 12:51:44PM +0100, Chris Wilson wrote:
> On Sun, 26 Aug 2012 21:46:01 +1000, Dave Airlie <airlied at gmail.com> wrote:
> > On Sun, Aug 26, 2012 at 9:43 PM, Alon Levy <alevy at redhat.com> wrote:
> > > ACPI is meant as a fallback, so it should be last.
> > 
> > eh no, acpi is never the fallback, its always the preferred way.

I guess I was confused by the comment:
 "acpi_video1", /* finally fallback to the generic acpi drivers */

> 
> Right, acpi works on far more machines than intel_backlight. If you want
> to override the automaticlly choose interface, how about an
>    Option "backlight" "intel_backlight"
> ?

Works for me, patch below. But I'm confused - wouldn't the
intel_backlight sys directory be non existant if the kernel found the
machine didn't support it? at least I thought that was the point - then
checking acpi last makes sense.

> -Chris
> 
> -- 
> Chris Wilson, Intel Open Source Technology Centre

commit 26abd7bb55f0962bd2cac0f7ed25c82dff746534
Author: Alon Levy <alevy at redhat.com>
Date:   Sun Aug 26 13:15:29 2012 +0200

    add OPTION_INTEL_BACKLIGHT
    
    Allow setting intel_backlight as the preferred backlight interface.
    
    This allows my Lenovo T510 to reach the minimal backlight (switched
    off), by using intel_backlight instead of acpi.
    
    Signed-off-by: Alon Levy <alevy at redhat.com>

diff --git a/src/intel_display.c b/src/intel_display.c
index 6580c8c..a3934bb 100644
--- a/src/intel_display.c
+++ b/src/intel_display.c
@@ -41,6 +41,7 @@
 
 #include "intel.h"
 #include "intel_bufmgr.h"
+#include "intel_options.h"
 #include "xf86drm.h"
 #include "xf86drmMode.h"
 #include "X11/Xatom.h"
@@ -248,26 +249,43 @@ intel_output_backlight_get_max(xf86OutputPtr output)
 	return max;
 }
 
+static Bool
+intel_output_try_backlight(xf86OutputPtr output, const char *interface)
+{
+	struct intel_output *intel_output = output->driver_private;
+	char path[BACKLIGHT_PATH_LEN];
+	struct stat buf;
+
+	sprintf(path, "%s/%s", BACKLIGHT_CLASS, interface);
+	if (!stat(path, &buf)) {
+		intel_output->backlight_iface = interface;
+		intel_output->backlight_max = intel_output_backlight_get_max(output);
+		if (intel_output->backlight_max > 0) {
+			intel_output->backlight_active_level = intel_output_backlight_get(output);
+			xf86DrvMsg(output->scrn->scrnIndex, X_INFO,
+				   "found backlight control interface %s\n", path);
+			return TRUE;
+		}
+	}
+	return FALSE;
+}
+
 static void
 intel_output_backlight_init(xf86OutputPtr output)
 {
 	struct intel_output *intel_output = output->driver_private;
+	intel_screen_private *intel = intel_get_screen_private(output->scrn);
 	int i;
 
+	if (xf86ReturnOptValBool(intel->Options, OPTION_INTEL_BACKLIGHT, FALSE)) {
+		if (intel_output_try_backlight(output, "intel_backlight")) {
+			return;
+		}
+	}
+
 	for (i = 0; backlight_interfaces[i] != NULL; i++) {
-		char path[BACKLIGHT_PATH_LEN];
-		struct stat buf;
-
-		sprintf(path, "%s/%s", BACKLIGHT_CLASS, backlight_interfaces[i]);
-		if (!stat(path, &buf)) {
-			intel_output->backlight_iface = backlight_interfaces[i];
-			intel_output->backlight_max = intel_output_backlight_get_max(output);
-			if (intel_output->backlight_max > 0) {
-				intel_output->backlight_active_level = intel_output_backlight_get(output);
-				xf86DrvMsg(output->scrn->scrnIndex, X_INFO,
-					   "found backlight control interface %s\n", path);
-				return;
-			}
+		if (intel_output_try_backlight(output, backlight_interfaces[i])) {
+			return;
 		}
 	}
 	intel_output->backlight_iface = NULL;
diff --git a/src/intel_options.c b/src/intel_options.c
index 7dbbc7e..c15b661 100644
--- a/src/intel_options.c
+++ b/src/intel_options.c
@@ -15,7 +15,8 @@ const OptionInfoRec intel_options[] = {
 	{OPTION_SWAPBUFFERS_WAIT, "SwapbuffersWait", OPTV_BOOLEAN,	{0},	1},
 	{OPTION_PREFER_OVERLAY, "XvPreferOverlay", OPTV_BOOLEAN, {0}, 0},
 	{OPTION_HOTPLUG,	"HotPlug",	OPTV_BOOLEAN,	{0},	1},
-	{OPTION_RELAXED_FENCING,"RelaxedFencing",	OPTV_BOOLEAN,	{0},	1},
+	{OPTION_RELAXED_FENCING,    "RelaxedFencing",	OPTV_BOOLEAN,	{0},	1},
+    {OPTION_INTEL_BACKLIGHT,    "IntelBacklight",   OPTV_BOOLEAN,   {0},    0},
 #ifdef INTEL_XVMC
 	{OPTION_XVMC,	"XvMC",		OPTV_BOOLEAN,	{0},	1},
 #endif
diff --git a/src/intel_options.h b/src/intel_options.h
index 6c16a07..0d6f4f6 100644
--- a/src/intel_options.h
+++ b/src/intel_options.h
@@ -22,6 +22,7 @@ enum intel_options {
 	OPTION_PREFER_OVERLAY,
 	OPTION_HOTPLUG,
 	OPTION_RELAXED_FENCING,
+    OPTION_INTEL_BACKLIGHT,
 #ifdef INTEL_XVMC
 	OPTION_XVMC,
 #endif