fix: don't use drmIsKMS

ardera · ardera · commit 8aef78fddccd · 2025-06-21T13:21:49.000+02:00
libdrm's drmIsKMS was added in libdrm 2.4.105: https://gitlab.freedesktop.org/mesa/libdrm/-/commit/523b3658aa8efa746417e916c987de23740ce313 Debian bullseye is still on 2.4.104, so it's unfortunately not present there.
diff --git a/src/kms/drmdev.c b/src/kms/drmdev.c
@@ -110,13 +110,16 @@ static bool is_kms_device(const char *path, const struct drmdev_file_interface *
         return false;
     }
 
-    if (!drmIsKMS(fd)) {
+    // Ideally we'd use drmIsKMS() here, but it's not available everywhere.
+
+    struct drm_mode_card_res res = { 0 };
+    if (drmIoctl(fd, DRM_IOCTL_MODE_GETRESOURCES, &res) != 0) {
         interface->close(fd, fd_metadata, userdata);
         return false;
     }
 
     interface->close(fd, fd_metadata, userdata);
-    return true;
+    return res.count_crtcs > 0 && res.count_connectors > 0 && res.count_encoders > 0;
 }
 
 static void assert_rotations_work() {

Original file line number	Diff line number	Diff line change
`@@ -110,13 +110,16 @@ static bool is_kms_device(const char path, const struct drmdev_file_interface `
`110`	`110`	`return false;`
`111`	`111`	`}`
`112`	`112`
`113`		`- if (!drmIsKMS(fd)) {`
	`113`	`+ // Ideally we'd use drmIsKMS() here, but it's not available everywhere.`
	`114`	`+`
	`115`	`+ struct drm_mode_card_res res = { 0 };`
	`116`	`+ if (drmIoctl(fd, DRM_IOCTL_MODE_GETRESOURCES, &res) != 0) {`
`114`	`117`	`interface->close(fd, fd_metadata, userdata);`
`115`	`118`	`return false;`
`116`	`119`	`}`
`117`	`120`
`118`	`121`	`interface->close(fd, fd_metadata, userdata);`
`119`		`- return true;`
	`122`	`+ return res.count_crtcs > 0 && res.count_connectors > 0 && res.count_encoders > 0;`
`120`	`123`	`}`
`121`	`124`
`122`	`125`	`static void assert_rotations_work() {`