[PATCH libdrm] xf86drm: Parse the separate files to retrieve the vendor/device info

[Emil Velikov]

From: Emil Velikov <emil.velikov at collabora.com>

Parsing config sysfs file wakes up the device. The latter of which may
be slow and isn't required to begin with.

Reading through config is/was required since the revision is not
available by other means, although with a kernel patch in the way we can
'cheat' temporarily.

That should be fine, since no open-source project has ever used the
value.

Cc: Michel Dänzer <michel.daenzer at amd.com>
Cc: Mauro Santos <registo.mailling at gmail.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=98502
Signed-off-by: Emil Velikov <emil.velikov at collabora.com>
---
Mauro can you apply this against libdrm and rebuild it. You do _not_
need to rebuild mesa afterwords.

Thanks
---
 xf86drm.c | 50 +++++++++++++++++++++++++++++++++++---------------
 1 file changed, 35 insertions(+), 15 deletions(-)

diff --git a/xf86drm.c b/xf86drm.c
index 52add5e..5a5100c 100644
--- a/xf86drm.c
+++ b/xf86drm.c
@@ -2950,25 +2950,45 @@ static int drmParsePciDeviceInfo(const char *d_name,
                                  drmPciDeviceInfoPtr device)
 {
 #ifdef __linux__
+#define ARRAY_SIZE(a) (sizeof(a) / sizeof((a)[0]))
+    static const char *attrs[] = {
+      "revision", /* XXX: make sure it's always first, see note below */
+      "vendor",
+      "device",
+      "subsystem_vendor",
+      "subsystem_device",
+    };
     char path[PATH_MAX + 1];
-    unsigned char config[64];
-    int fd, ret;
+    unsigned int data[ARRAY_SIZE(attrs)];
+    FILE *fp;
+    int ret;
 
-    snprintf(path, PATH_MAX, "/sys/class/drm/%s/device/config", d_name);
-    fd = open(path, O_RDONLY);
-    if (fd < 0)
-        return -errno;
+    for (unsigned i = 0; i < ARRAY_SIZE(attrs); i++) {
+        snprintf(path, PATH_MAX, "/sys/class/drm/%s/device/%s",
+                 d_name, attrs[i]);
+        fp = fopen(path, "r");
+        if (!fp) {
+            /* Note: First we check the revision, since older kernels
+             * may not have it. Default to zero in such cases. */
+            if (i == 0) {
+                data[i] = 0;
+                continue;
+            }
+            return -errno;
+        }
 
-    ret = read(fd, config, sizeof(config));
-    close(fd);
-    if (ret < 0)
-        return -errno;
+        ret = fscanf(fp, "%x", &data[i]);
+        fclose(fp);
+        if (ret != 1)
+            return -errno;
+
+    }
 
-    device->vendor_id = config[0] | (config[1] << 8);
-    device->device_id = config[2] | (config[3] << 8);
-    device->revision_id = config[8];
-    device->subvendor_id = config[44] | (config[45] << 8);
-    device->subdevice_id = config[46] | (config[47] << 8);
+    device->revision_id = data[0] & 0xff;
+    device->vendor_id = data[1] & 0xffff;
+    device->device_id = data[2] & 0xffff;
+    device->subvendor_id = data[3] & 0xffff;
+    device->subdevice_id = data[4] & 0xffff;
 
     return 0;
 #else
-- 
2.10.0