drm_common: remove hard dependency on drmIsKMS()

ae768a1e141eb88243e46757d41ca0cada9502b4 forgot to bump the required
libdrm version however Debian 11 just barely misses the requirement,
which is a good reason not to require it unconditionally anyway.

3 files changed, 30 insertions, 5 deletions

diff --git a/meson.build b/meson.build
index 4273ebcdae..3d7b85a0ee 100644
--- a/meson.build
+++ b/meson.build
@@ -952,6 +952,15 @@ if drm['use']
                      'video/out/vo_drm.c')
 endif
 
+# This can be removed roughly when Debian 12 is released.
+drm_is_kms = {
+    'name': 'drm-is-kms',
+    'use': drm['use'] and drm['deps'].version().version_compare('>= 2.4.105')
+}
+if drm_is_kms['use']
+    features += drm_is_kms['name']
+endif
+
 gbm = dependency('gbm', version: '>=17.1.0', required: get_option('gbm'))
 if gbm.found()
     dependencies += gbm
@@ -1745,6 +1754,7 @@ conf_data.set10('HAVE_DMABUF_INTEROP_GL', dmabuf_interop_gl['use'])
 conf_data.set10('HAVE_DMABUF_INTEROP_PL', dmabuf_interop_pl['use'])
 conf_data.set10('HAVE_DOS_PATHS', win32)
 conf_data.set10('HAVE_DRM', drm['use'])
+conf_data.set10('HAVE_DRM_IS_KMS', drm_is_kms['use'])
 conf_data.set10('HAVE_DVBIN', dvbin.allowed())
 conf_data.set10('HAVE_DVDNAV', dvdnav.found() and dvdread.found())
 conf_data.set10('HAVE_EGL', egl['use'])
diff --git a/video/out/drm_common.c b/video/out/drm_common.c
index b2bbc03ceb..d6511b7100 100644
--- a/video/out/drm_common.c
+++ b/video/out/drm_common.c
@@ -523,6 +523,19 @@ static int open_card_path(const char *path)
     return open(path, O_RDWR | O_CLOEXEC);
 }
 
+static bool card_supports_kms(const char *path)
+{
+#if HAVE_DRM_IS_KMS
+    int fd = open_card_path(path);
+    bool ret = fd != -1 && drmIsKMS(fd);
+    if (fd != -1)
+        close(fd);
+    return ret;
+#else
+    return true;
+#endif
+}
+
 static char *get_primary_device_path(struct mp_log *log, int *card_no)
 {
     drmDevice *devices[DRM_MAX_MINOR] = { 0 };
@@ -558,11 +571,7 @@ static char *get_primary_device_path(struct mp_log *log, int *card_no)
 
         const char *primary_node_path = dev->nodes[DRM_NODE_PRIMARY];
 
-        int fd = open_card_path(primary_node_path);
-        const int is_kms = fd != -1 && drmIsKMS(fd);
-        if (fd != -1)
-            close(fd);
-        if (!is_kms) {
+        if (!card_supports_kms(primary_node_path)) {
             if (card_no_given) {
                 mp_err(log,
                        "DRM card number %d given, yet it does not support "
diff --git a/wscript b/wscript
index 7341b71d25..f13b9f98d6 100644
--- a/wscript
+++ b/wscript
@@ -792,6 +792,12 @@ video_output_features = [
         'desc': 'dmabuf libplacebo interop',
         'deps': 'vaapi-libplacebo',
         'func': check_true,
+    }, {
+        # This can be removed roughly when Debian 12 is released.
+        'name': 'drm-is-kms',
+        'desc': 'drmIsKMS() function',
+        'deps': 'drm',
+        'func': check_pkg_config('libdrm', '>= 2.4.105'),
     }
 ]