[PATCH v2] xf86: Fix non-PCI configuration-less setups

[Thierry Reding]

For non-PCI video devices, such as those found on many ARM embedded
systems, the X server currently requires the BusID option to specify the
full path to the DRM device's sysfs node in order to properly match it
against the probed platform devices.

In order to allow X to start up properly if either the BusID option was
omitted or no configuration is present at all, the first video device is
used by default.

Signed-off-by: Thierry Reding <thierry.reding at avionic-design.de>
---
Changes in v2:
- Add additional checks for safety (I don't think numDevs will ever be 0
  since a default will be generated if no configuration is present, but
  it doesn't hurt to check anyway). Without these checks there is a
  possibility of the X server crashing if no platform devices have been
  found.

 hw/xfree86/common/xf86platformBus.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/hw/xfree86/common/xf86platformBus.c b/hw/xfree86/common/xf86platformBus.c
index 0525e39..599d84a 100644
--- a/hw/xfree86/common/xf86platformBus.c
+++ b/hw/xfree86/common/xf86platformBus.c
@@ -377,6 +377,14 @@ xf86platformProbeDev(DriverPtr drvp)
             continue;
     }
 
+    /*
+     * If all of the above fails, which can happen if X was started without
+     * configuration or if BusID wasn't set for non-PCI devices, use the first
+     * device by default.
+     */
+    if (!foundScreen && xf86_num_platform_devices > 0 && numDevs > 0)
+        foundScreen = probeSingleDevice(&xf86_platform_devices[0], drvp, devList[0], 0);
+
     /* if autoaddgpu devices is enabled then go find a few more and add them as GPU screens */
     if (xf86Info.autoAddGPU && numDevs) {
         for (j = 0; j < xf86_num_platform_devices; j++) {
-- 
1.7.12.3