[PATCH libdrm 05/10] xf86drm: introduce a get_real_pci_path() helper

[Emil Velikov <emil.l.velikov@xxxxxxxxx>]

From: Emil Velikov <emil.velikov@xxxxxxxxxxxxx>

Introduce a helper which gets the real sysfs path for the given pci
device.

In other words, instead opening the /sys/dev/char/*/device symlink, we
opt for the actual /sys/devices/pci*/*/

It folds three (nearly identical) snprintf's and paves the way of adding
extra devices (see next patch) a piece of pie.

Signed-off-by: Emil Velikov <emil.velikov@xxxxxxxxxxxxx>
---
 xf86drm.c | 62 ++++++++++++++++++++++++++++++++++++++++++++-----------
 1 file changed, 50 insertions(+), 12 deletions(-)

diff --git a/xf86drm.c b/xf86drm.c
index d4810740..8ccd528f 100644
--- a/xf86drm.c
+++ b/xf86drm.c
@@ -2992,16 +2992,37 @@ static int drmParseSubsystemType(int maj, int min)
 #endif
 }
 
+static char *
+get_real_pci_path(int maj, int min)
+{
+    char path[PATH_MAX + 1];
+    char *real_path = malloc(PATH_MAX);
+
+    if (!real_path)
+        return NULL;
+
+    snprintf(path, sizeof(path), "/sys/dev/char/%d:%d/device", maj, min);
+    if (!realpath(path, real_path)) {
+        free(real_path);
+        return NULL;
+    }
+
+    return real_path;
+}
+
 static int drmParsePciBusInfo(int maj, int min, drmPciBusInfoPtr info)
 {
 #ifdef __linux__
     unsigned int domain, bus, dev, func;
-    char path[PATH_MAX + 1], *value;
+    char *real_path, *value;
     int num;
 
-    snprintf(path, sizeof(path), "/sys/dev/char/%d:%d/device", maj, min);
+    real_path = get_real_pci_path(maj, min);
+    if (!real_path)
+        return -ENOENT;
 
-    value = sysfs_uevent_get(path, "PCI_SLOT_NAME");
+    value = sysfs_uevent_get(real_path, "PCI_SLOT_NAME");
+    free(real_path);
     if (!value)
         return -ENOENT;
 
@@ -3114,24 +3135,32 @@ static int parse_separate_sysfs_files(int maj, int min,
       "subsystem_vendor",
       "subsystem_device",
     };
-    char path[PATH_MAX + 1];
+    char path[PATH_MAX + 1], *real_path;
     unsigned int data[ARRAY_SIZE(attrs)];
     FILE *fp;
     int ret;
 
+    real_path = get_real_pci_path(maj, min);
+    if (!real_path)
+        return -ENOENT;
+
     for (unsigned i = ignore_revision ? 1 : 0; i < ARRAY_SIZE(attrs); i++) {
-        snprintf(path, PATH_MAX, "/sys/dev/char/%d:%d/device/%s", maj, min,
-                 attrs[i]);
+        snprintf(path, PATH_MAX, "%s/%s", real_path, attrs[i]);
         fp = fopen(path, "r");
-        if (!fp)
+        if (!fp) {
+            free(real_path);
             return -errno;
+        }
 
         ret = fscanf(fp, "%x", &data[i]);
         fclose(fp);
-        if (ret != 1)
+        if (ret != 1) {
+            free(real_path);
             return -errno;
+        }
 
     }
+    free(real_path);
 
     device->revision_id = ignore_revision ? 0xff : data[0] & 0xff;
     device->vendor_id = data[1] & 0xffff;
@@ -3145,19 +3174,28 @@ static int parse_separate_sysfs_files(int maj, int min,
 static int parse_config_sysfs_file(int maj, int min,
                                    drmPciDeviceInfoPtr device)
 {
-    char path[PATH_MAX + 1];
+    char path[PATH_MAX + 1], *real_path;
     unsigned char config[64];
     int fd, ret;
 
-    snprintf(path, PATH_MAX, "/sys/dev/char/%d:%d/device/config", maj, min);
+    real_path = get_real_pci_path(maj, min);
+    if (!real_path)
+        return -ENOENT;
+
+    snprintf(path, PATH_MAX, "%s/config", real_path);
     fd = open(path, O_RDONLY);
-    if (fd < 0)
+    if (fd < 0) {
+        free(real_path);
         return -errno;
+    }
 
     ret = read(fd, config, sizeof(config));
     close(fd);
-    if (ret < 0)
+    if (ret < 0) {
+        free(real_path);
         return -errno;
+    }
+    free(real_path);
 
     device->vendor_id = config[0] | (config[1] << 8);
     device->device_id = config[2] | (config[3] << 8);
-- 
2.18.0

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