loader: add optional /sys filesystem method for PCI identification.

Introduce a simple PCI identification method of looking up the answer
the /sys filesystem (available on Linux).  Attempted after libudev, but
before DRM.

Disabled by default (available only when the --enable-sysfs configure
option is specified).

Signed-off-by: Gary Wong <gtw@gnu.org>
Acked-by: Emil Velikov <emil.l.velikov@gmail.com>

2 files changed, 137 insertions, 11 deletions

diff --git a/configure.ac b/configure.ac
index bee85a13154..9c64400a73b 100644
--- a/configure.ac
+++ b/configure.ac
@@ -870,14 +870,21 @@ fi
 
 case "$host_os" in
 linux*)
-    need_libudev=yes ;;
+    need_pci_id=yes ;;
 *)
-    need_libudev=no ;;
+    need_pci_id=no ;;
 esac
 
 PKG_CHECK_MODULES([LIBUDEV], [libudev >= $LIBUDEV_REQUIRED],
                   have_libudev=yes, have_libudev=no)
 
+AC_ARG_ENABLE([sysfs],
+    [AS_HELP_STRING([--enable-sysfs],
+        [enable /sys PCI identification @<:@default=disabled@:>@])],
+    [have_sysfs="$enableval"],
+    [have_sysfs=no]
+)
+
 if test "x$enable_dri" = xyes; then
     if test "$enable_static" = yes; then
         AC_MSG_ERROR([Cannot use static libraries for DRI drivers])
@@ -973,8 +980,15 @@ xyesno)
     ;;
 esac
 
+have_pci_id=no
 if test "$have_libudev" = yes; then
     DEFINES="$DEFINES -DHAVE_LIBUDEV"
+    have_pci_id=yes
+fi
+
+if test "$have_sysfs" = yes; then
+    DEFINES="$DEFINES -DHAVE_SYSFS"
+    have_pci_id=yes
 fi
 
 # This is outside the case (above) so that it is invoked even for non-GLX
@@ -1076,8 +1090,8 @@ if test "x$enable_dri" = xyes; then
             DEFINES="$DEFINES -DHAVE_DRI3"
         fi
 
-        if test "x$have_libudev" != xyes; then
-            AC_MSG_ERROR([libudev-dev required for building DRI])
+        if test "x$have_pci_id" != xyes; then
+            AC_MSG_ERROR([libudev-dev or sysfs required for building DRI])
         fi
 
         case "$host_cpu" in
@@ -1252,8 +1266,8 @@ if test "x$enable_gbm" = xauto; then
     esac
 fi
 if test "x$enable_gbm" = xyes; then
-    if test "x$need_libudev$have_libudev" = xyesno; then
-        AC_MSG_ERROR([gbm requires udev >= $LIBUDEV_REQUIRED])
+    if test "x$need_pci_id$have_pci_id" = xyesno; then
+        AC_MSG_ERROR([gbm requires udev >= $LIBUDEV_REQUIRED or sysfs])
     fi
 
     if test "x$enable_dri" = xyes; then
@@ -1271,7 +1285,7 @@ if test "x$enable_gbm" = xyes; then
     fi
 fi
 AM_CONDITIONAL(HAVE_GBM, test "x$enable_gbm" = xyes)
-if test "x$need_libudev" = xyes; then
+if test "x$need_pci_id$have_libudev" = xyesyes; then
     GBM_PC_REQ_PRIV="libudev >= $LIBUDEV_REQUIRED"
 else
     GBM_PC_REQ_PRIV=""
@@ -1560,9 +1574,9 @@ for plat in $egl_platforms; do
 		;;
 	esac
 
-        case "$plat$need_libudev$have_libudev" in
+        case "$plat$need_pci_id$have_pci_id" in
                 waylandyesno|drmyesno)
-                    AC_MSG_ERROR([cannot build $plat platform without udev >= $LIBUDEV_REQUIRED]) ;;
+                    AC_MSG_ERROR([cannot build $plat platform without udev >= $LIBUDEV_REQUIRED or sysfs]) ;;
         esac
 done
 
@@ -1843,8 +1857,8 @@ gallium_require_llvm() {
 
 gallium_require_drm_loader() {
     if test "x$enable_gallium_loader" = xyes; then
-        if test "x$need_libudev$have_libudev" = xyesno; then
-            AC_MSG_ERROR([Gallium drm loader requires libudev >= $LIBUDEV_REQUIRED])
+        if test "x$need_pci_id$have_pci_id" = xyesno; then
+            AC_MSG_ERROR([Gallium drm loader requires libudev >= $LIBUDEV_REQUIRED or sysfs])
         fi
         if test "x$have_libdrm" != xyes; then
             AC_MSG_ERROR([Gallium drm loader requires libdrm >= $LIBDRM_REQUIRED])
diff --git a/src/loader/loader.c b/src/loader/loader.c
index 52be7061c19..0f262653b29 100644
--- a/src/loader/loader.c
+++ b/src/loader/loader.c
@@ -71,6 +71,10 @@
 #include <assert.h>
 #include <dlfcn.h>
 #endif
+#ifdef HAVE_SYSFS
+#include <sys/stat.h>
+#include <sys/types.h>
+#endif
 #include "loader.h"
 
 #ifndef __NOT_HAVE_DRM_H
@@ -212,6 +216,66 @@ out:
 }
 #endif
 
+#if defined(HAVE_SYSFS)
+static int
+dev_node_from_fd(int fd, unsigned int *maj, unsigned int *min)
+{
+   struct stat buf;
+
+   if (fstat(fd, &buf) < 0) {
+      log_(_LOADER_WARNING, "MESA-LOADER: failed to stat fd %d\n", fd);
+      return -1;
+   }
+
+   if (!S_ISCHR(buf.st_mode)) {
+      log_(_LOADER_WARNING, "MESA-LOADER: fd %d not a character device\n", fd);
+      return -1;
+   }
+
+   *maj = major(buf.st_rdev);
+   *min = minor(buf.st_rdev);
+
+   return 0;
+}
+
+static int
+sysfs_get_pci_id_for_fd(int fd, int *vendor_id, int *chip_id)
+{
+   unsigned int maj, min;
+   FILE *f;
+   char buf[0x40];
+
+   if (dev_node_from_fd(fd, &maj, &min) < 0) {
+      *chip_id = -1;
+      return 0;
+   }
+
+   snprintf(buf, sizeof(buf), "/sys/dev/char/%d:%d/device/vendor", maj, min);
+   if (!(f = fopen(buf, "r"))) {
+      *chip_id = -1;
+      return 0;
+   }
+   if (fscanf(f, "%x", vendor_id) != 1) {
+      *chip_id = -1;
+      fclose(f);
+      return 0;
+   }
+   fclose(f);
+   snprintf(buf, sizeof(buf), "/sys/dev/char/%d:%d/device/device", maj, min);
+   if (!(f = fopen(buf, "r"))) {
+      *chip_id = -1;
+      return 0;
+   }
+   if (fscanf(f, "%x", chip_id) != 1) {
+      *chip_id = -1;
+      fclose(f);
+      return 0;
+   }
+   fclose(f);
+   return 1;
+}
+#endif
+
 #if !defined(__NOT_HAVE_DRM_H)
 /* for i915 */
 #include <i915_drm.h>
@@ -291,6 +355,10 @@ loader_get_pci_id_for_fd(int fd, int *vendor_id, int *chip_id)
    if (libudev_get_pci_id_for_fd(fd, vendor_id, chip_id))
       return 1;
 #endif
+#if HAVE_SYSFS
+   if (sysfs_get_pci_id_for_fd(fd, vendor_id, chip_id))
+      return 1;
+#endif
 #if !defined(__NOT_HAVE_DRM_H)
    if (drm_get_pci_id_for_fd(fd, vendor_id, chip_id))
       return 1;
@@ -332,6 +400,46 @@ out:
 #endif
 
 
+#if HAVE_SYSFS
+static char *
+sysfs_get_device_name_for_fd(int fd)
+{
+   char *device_name = NULL;
+   unsigned int maj, min;
+   FILE *f;
+   char buf[0x40];
+   static const char match[9] = "\0DEVNAME=";
+   int expected = 1;
+
+   if (dev_node_from_fd(fd, &maj, &min) < 0)
+      return NULL;
+
+   snprintf(buf, sizeof(buf), "/sys/dev/char/%d:%d/uevent", maj, min);
+   if (!(f = fopen(buf, "r")))
+       return NULL;
+
+   while (expected < sizeof(match)) {
+      int c = getc(f);
+
+      if (c == EOF) {
+         fclose(f);
+         return NULL;
+      } else if (c == match[expected] )
+         expected++;
+      else
+         expected = 0;
+   }
+
+   strcpy(buf, "/dev/");
+   if (fgets(buf + 5, sizeof(buf) - 5, f))
+      device_name = strdup(buf);
+
+   fclose(f);
+   return device_name;
+}
+#endif
+
+
 char *
 loader_get_device_name_for_fd(int fd)
 {
@@ -341,6 +449,10 @@ loader_get_device_name_for_fd(int fd)
    if ((result = libudev_get_device_name_for_fd(fd)))
       return result;
 #endif
+#if HAVE_SYSFS
+   if ((result = sysfs_get_device_name_for_fd(fd)))
+      return result;
+#endif
    return result;
 }