[PATCH libdrm 2/2] xf86drm: fix subsystem type lookup for virtio mmio-based devices

[Mikhail Golubev <Mikhail.Golubev@xxxxxxxxxxxxxxx>]

From: Vasyl Vavrychuk <vasyl.vavrychuk@xxxxxxxxxxxxxxx>

Currently the code assumes that a virtio based device is always located
on the PCI bus.

Modify the parser to make it check the device's parent directory to
determine on which bus it is located.

Output for virtio-pci is the PCI bus.
Output for virtio-mmio is the Platform bus.

Signed-off-by: Vasyl Vavrychuk <vasyl.vavrychuk@xxxxxxxxxxxxxxx>
Signed-off-by: Mikhail Golubev <Mikhail.Golubev@xxxxxxxxxxxxxxx>
---
 xf86drm.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/xf86drm.c b/xf86drm.c
index b1479128..1b22efe4 100644
--- a/xf86drm.c
+++ b/xf86drm.c
@@ -3005,10 +3005,20 @@ static int drmParseSubsystemType(int maj, int min)
 {
 #ifdef __linux__
     char path[PATH_MAX + 1] = "";
+    char real_path[PATH_MAX + 1] = "";
+    int subsystem_type;
 
     snprintf(path, PATH_MAX, "/sys/dev/char/%d:%d/device", maj, min);
+    if (!realpath(path, real_path))
+        return -errno;
+    strncpy(path, real_path, PATH_MAX);
 
-    return get_subsystem_type(path);
+    subsystem_type = get_subsystem_type(path);
+    if (subsystem_type == DRM_BUS_VIRTIO) {
+        strncat(path, "/..", PATH_MAX);
+        subsystem_type = get_subsystem_type(path);
+    }
+    return subsystem_type;
 #elif defined(__OpenBSD__) || defined(__DragonFly__)
     return DRM_BUS_PCI;
 #else
@@ -3710,7 +3720,6 @@ process_device(drmDevicePtr *device, const char *d_name,
 
     switch (subsystem_type) {
     case DRM_BUS_PCI:
-    case DRM_BUS_VIRTIO:
         return drmProcessPciDevice(device, node, node_type, maj, min,
                                    fetch_deviceinfo, flags);
     case DRM_BUS_USB:
-- 
2.23.0

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