drm: parse edid using libdisplay-info

libdrm unfortunately doesn't give us what is actually supported by the
connector in question. To do that, we would have to parse the edid blob.
Use libdisplay-info to do this and make it required for drm support.
Using what we get back from the library, we can do a bit of sanity
checking for hdr metadata to make sure that the display in question can
handle it before we try setting the metadata. Strictly speaking,
libdisplay-info has stuff for dynamic metadata that we could potentially
use, but as a first pass and for simplicity, only static is considered
for now.

meson.build

@@ -935,9 +935,11 @@ if features['direct3d']
 endif
 
 drm = dependency('libdrm', version: '>= 2.4.105', required: get_option('drm'))
-features += {'drm': drm.found() and (features['vt.h'] or features['consio.h'] or features['wsdisplay-usl-io.h'])}
+libdisplay_info = dependency('libdisplay-info', version: '>= 0.1.1', required: get_option('drm'))
+features += {'drm': drm.found() and libdisplay_info.found() and
+             (features['vt.h'] or features['consio.h'] or features['wsdisplay-usl-io.h'])}
 if features['drm']
-    dependencies += drm
+    dependencies += [drm, libdisplay_info]
     sources += files('video/drmprime.c',
                      'video/out/drm_atomic.c',
                      'video/out/drm_common.c',

video/out/drm_common.c

@@ -617,6 +617,83 @@ success:
     return true;
 }
 
+static void setup_edid(struct vo_drm_state *drm)
+{
+    drmModePropertyBlobRes *blob = NULL;
+    for (int i = 0; i < drm->connector->count_props; ++i) {
+        drmModePropertyRes *prop = drmModeGetProperty(drm->fd, drm->connector->props[i]);
+        if (prop && strcmp(prop->name, "EDID") == 0)
+            blob = drmModeGetPropertyBlob(drm->fd, drm->connector->prop_values[i]);
+        drmModeFreeProperty(prop);
+        if (blob)
+            break;
+    }
+    if (!blob) {
+        MP_VERBOSE(drm, "Unable to get EDID blob from connector.\n");
+        return;
+    }
+
+    drm->info = di_info_parse_edid(blob->data, blob->length);
+    if (!drm->info) {
+        MP_VERBOSE(drm, "Failed to parse EDID info: %s\n", mp_strerror(errno));
+        goto done;
+    }
+
+    const struct di_edid *edid = di_info_get_edid(drm->info);
+    if (!edid) {
+        MP_VERBOSE(drm, "Failed to get EDID info: %s\n", mp_strerror(errno));
+        goto done;
+    }
+
+    drm->chromaticity = di_edid_get_chromaticity_coords(edid);
+
+    const struct di_edid_cta *cta;
+    const struct di_edid_ext *const *exts = di_edid_get_extensions(edid);
+    while (*exts && !(cta = di_edid_ext_get_cta(*exts++)));
+
+    if (!cta) {
+        MP_VERBOSE(drm, "Unable to find CTA-861 extension block.\n");
+        goto done;
+    }
+
+    const struct di_cta_data_block *const *blocks = di_edid_cta_get_data_blocks(cta);
+    for (int i = 0; *blocks && blocks[i]; ++i) {
+        if (!drm->colorimetry)
+            drm->colorimetry = di_cta_data_block_get_colorimetry(blocks[i]);
+        if (!drm->hdr_static_metadata)
+            drm->hdr_static_metadata = di_cta_data_block_get_hdr_static_metadata(blocks[i]);
+        if (drm->colorimetry && drm->hdr_static_metadata)
+            break;
+    }
+
+done:
+    if (blob)
+        drmModeFreePropertyBlob(blob);
+}
+
+static bool target_params_supported_by_display(struct vo_drm_state *drm)
+{
+    if (!drm->chromaticity || !drm->colorimetry || !drm->hdr_static_metadata)
+        return false;
+
+    const struct di_cta_hdr_static_metadata_block *hdr_static_metadata = drm->hdr_static_metadata;
+    enum pl_color_transfer trc = drm->target_params.color.transfer;
+
+    if (!pl_color_transfer_is_hdr(trc) && !hdr_static_metadata->eotfs->traditional_sdr)
+        return false;
+
+    if (pl_color_transfer_is_hdr(trc) && !drm->colorimetry->bt2020_rgb)
+        return false;
+
+    if (trc == PL_COLOR_TRC_PQ && !hdr_static_metadata->eotfs->pq)
+        return false;
+
+    if (trc == PL_COLOR_TRC_HLG && !hdr_static_metadata->eotfs->hlg)
+        return false;
+
+    return true;
+}
+
 static bool all_digits(const char *str)
 {
     if (str == NULL || str[0] == '\0') {
@@ -1034,6 +1111,8 @@ bool vo_drm_init(struct vo *vo)
     if (!setup_mode(drm))
         goto err;
 
+    setup_edid(drm);
+
     // Universal planes allows accessing all the planes (including primary)
     if (drmSetClientCap(drm->fd, DRM_CLIENT_CAP_UNIVERSAL_PLANES, 1)) {
         MP_ERR(drm, "Failed to set Universal planes capability\n");
@@ -1079,6 +1158,9 @@ void vo_drm_uninit(struct vo *vo)
     restore_sdr(drm);
     destroy_hdr_blob(drm);
 
+    if (drm->info)
+        di_info_destroy(drm->info);
+
     vo_drm_release_crtc(drm);
     if (drm->vt_switcher_active)
         vt_switcher_destroy(&drm->vt_switcher);
@@ -1283,10 +1365,11 @@ bool vo_drm_set_hdr_metadata(struct vo *vo, bool force_sdr)
 
     destroy_hdr_blob(drm);
     drm->target_params = target_params;
+    bool use_sdr = !target_params_supported_by_display(drm) || force_sdr;
 
     // For any HDR, the BT2020 drm colorspace is the only one that works in practice.
     struct drm_atomic_context *atomic_ctx = drm->atomic_context;
-    int colorspace = !force_sdr && pl_color_space_is_hdr(&drm->target_params.color) ?
+    int colorspace = !use_sdr && pl_color_space_is_hdr(&drm->target_params.color) ?
                      DRM_MODE_COLORIMETRY_BT2020_RGB : DRM_MODE_COLORIMETRY_DEFAULT;
     drm_object_set_property(atomic_ctx->request, atomic_ctx->connector, "Colorspace", colorspace);
 
@@ -1295,7 +1378,7 @@ bool vo_drm_set_hdr_metadata(struct vo *vo, bool force_sdr)
         .metadata_type = HDMI_STATIC_METADATA_TYPE1,
         .hdmi_metadata_type1.metadata_type = HDMI_STATIC_METADATA_TYPE1,
 
-        .hdmi_metadata_type1.eotf = force_sdr ? HDMI_EOTF_TRADITIONAL_GAMMA_SDR : eotf_map[target_params.color.transfer],
+        .hdmi_metadata_type1.eotf = use_sdr ? HDMI_EOTF_TRADITIONAL_GAMMA_SDR : eotf_map[target_params.color.transfer],
 
         .hdmi_metadata_type1.display_primaries[0].x = lrintf(hdr->prim.red.x * DRM_PRIM_FACTOR),
         .hdmi_metadata_type1.display_primaries[0].y = lrintf(hdr->prim.red.y * DRM_PRIM_FACTOR),

video/out/drm_common.h

@@ -22,6 +22,10 @@
 #include <xf86drm.h>
 #include <xf86drmMode.h>
 
+#include <libdisplay-info/cta.h>
+#include <libdisplay-info/edid.h>
+#include <libdisplay-info/info.h>
+
 #include "video/mp_image.h"
 #include "vo.h"
 
@@ -129,6 +133,12 @@ struct vo_drm_state {
     struct vo *vo;
     struct vt_switcher vt_switcher;
 
+    // libdisplay-info edid stuff
+    struct di_info *info;
+    const struct di_edid_chromaticity_coords *chromaticity;
+    const struct di_cta_hdr_static_metadata_block *hdr_static_metadata;
+    const struct di_cta_colorimetry_block *colorimetry;
+
     bool active;
     bool paused;
     bool still;