devices: Use path to check device type

FreeBSD device numbers cannot be used to check the type of a device, as
they are merely unique filesystem IDs.

As the paths we use have been sanitized with realpath, we can simply use
the path to check if a requested file is an evdev or drm device. This
also allows us to make the check before the file is opened.

1 files changed, 21 insertions, 1 deletions

diff --git a/common/drm.c b/common/drm.c
index 3234e81..684a925 100644
--- a/common/drm.c
+++ b/common/drm.c
@@ -1,10 +1,12 @@
+#include <string.h>
 #include <sys/ioctl.h>
 #include <sys/types.h>
 
-#ifdef __linux__
+#if defined(__linux__)
 #include <sys/sysmacros.h>
 #endif
 
+#include "compiler.h"
 #include "drm.h"
 
 // From libdrm
@@ -21,6 +23,24 @@ int drm_drop_master(int fd) {
 	return ioctl(fd, DRM_IOCTL_DROP_MASTER, 0);
 }
 
+static int path_is_drm_card(const char *path) {
+	static const char prefix[] = "/dev/dri/card";
+	static const int prefixlen = STRLEN(prefix);
+	return strncmp(prefix, path, prefixlen) == 0;
+}
+
+static int path_is_drm_render(const char *path) {
+	static const char prefix[] = "/dev/dri/renderD";
+	static const int prefixlen = STRLEN(prefix);
+	return strncmp(prefix, path, prefixlen) == 0;
+}
+
+int path_is_drm(const char *path) {
+	return path_is_drm_card(path) || path_is_drm_render(path);
+}
+
+#if defined(__linux__)
 int dev_is_drm(dev_t device) {
 	return major(device) == 226;
 }
+#endif