From 3df8a7f01abffbfcb93683c20d66987999d1a4d1 Mon Sep 17 00:00:00 2001
From: Emil Velikov <emil.velikov@collabora.com>
Date: Wed, 23 Jan 2019 09:44:07 +0000
Subject: [PATCH] xf86drm: fallback to MODALIAS for OF less platform devices

Some devices can lack OF data or it may not be available in the uevent
file. Fallback to the MODALIAS data in those cases.

We strip any leading "MODALIAS=.*:" thus the resulting information is
compatible with existing code in Mesa.

v2: foo -> tmp_name

Signed-off-by: Emil Velikov <emil.velikov@collabora.com>
Tested-by: Lucas Stach <l.stach@pengutronix.de> (v1)
---
 xf86drm.c | 55 ++++++++++++++++++++++++++++++++++++++++++-------------
 1 file changed, 42 insertions(+), 13 deletions(-)

diff --git a/xf86drm.c b/xf86drm.c
index c4a2b424..6da8e6b1 100644
--- a/xf86drm.c
+++ b/xf86drm.c
@@ -3513,15 +3513,28 @@ free_device:
 static int drmParsePlatformBusInfo(int maj, int min, drmPlatformBusInfoPtr info)
 {
 #ifdef __linux__
-    char path[PATH_MAX + 1], *name;
+    char path[PATH_MAX + 1], *name, *tmp_name;
 
     snprintf(path, sizeof(path), "/sys/dev/char/%d:%d/device", maj, min);
 
     name = sysfs_uevent_get(path, "OF_FULLNAME");
-    if (!name)
-        return -ENOENT;
+    tmp_name = name;
+    if (!name) {
+        /* If the device lacks OF data, pick the MODALIAS info */
+        name = sysfs_uevent_get(path, "MODALIAS");
+        if (!name)
+            return -ENOENT;
 
-    strncpy(info->fullname, name, DRM_PLATFORM_DEVICE_NAME_LEN);
+        /* .. and strip the MODALIAS=[platform,usb...]: part. */
+        tmp_name = strrchr(name, ':');
+        if (!tmp_name) {
+            free(name);
+            return -ENOENT;
+        }
+        tmp_name++;
+    }
+
+    strncpy(info->fullname, tmp_name, DRM_PLATFORM_DEVICE_NAME_LEN);
     info->fullname[DRM_PLATFORM_DEVICE_NAME_LEN - 1] = '\0';
     free(name);
 
@@ -3536,18 +3549,20 @@ static int drmParsePlatformDeviceInfo(int maj, int min,
                                       drmPlatformDeviceInfoPtr info)
 {
 #ifdef __linux__
-    char path[PATH_MAX + 1], *value;
+    char path[PATH_MAX + 1], *value, *tmp_name;
     unsigned int count, i;
     int err;
 
     snprintf(path, sizeof(path), "/sys/dev/char/%d:%d/device", maj, min);
 
     value = sysfs_uevent_get(path, "OF_COMPATIBLE_N");
-    if (!value)
-        return -ENOENT;
-
-    sscanf(value, "%u", &count);
-    free(value);
+    if (value) {
+        sscanf(value, "%u", &count);
+        free(value);
+    } else {
+        /* Assume one entry if the device lack OF data */
+        count = 1;
+    }
 
     info->compatible = calloc(count + 1, sizeof(*info->compatible));
     if (!info->compatible)
@@ -3555,12 +3570,26 @@ static int drmParsePlatformDeviceInfo(int maj, int min,
 
     for (i = 0; i < count; i++) {
         value = sysfs_uevent_get(path, "OF_COMPATIBLE_%u", i);
+        tmp_name = value;
         if (!value) {
-            err = -ENOENT;
-            goto free;
+            /* If the device lacks OF data, pick the MODALIAS info */
+            value = sysfs_uevent_get(path, "MODALIAS");
+            if (!value) {
+                err = -ENOENT;
+                goto free;
+            }
+
+            /* .. and strip the MODALIAS=[platform,usb...]: part. */
+            tmp_name = strrchr(value, ':');
+            if (!tmp_name) {
+                free(value);
+                return -ENOENT;
+            }
+            tmp_name = strdup(tmp_name + 1);
+            free(value);
         }
 
-        info->compatible[i] = value;
+        info->compatible[i] = tmp_name;
     }
 
     return 0;