drm/edid: add helper function to detect monitor audio capability
To help to determine if digital display port needs to enable
audio output or not. This one adds a helper to get monitor's
audio capability via EDID CEA extension block.
Tested-by: Wu Fengguang <fengguang.wu@intel.com>
Signed-off-by: Zhenyu Wang <zhenyuw@linux.intel.com>
Reviewed-by: Adam Jackson <ajax@redhat.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
index fd033eb..c1a2621 100644
--- a/drivers/gpu/drm/drm_edid.c
+++ b/drivers/gpu/drm/drm_edid.c
@@ -1267,7 +1267,35 @@
}
#define HDMI_IDENTIFIER 0x000C03
+#define AUDIO_BLOCK 0x01
#define VENDOR_BLOCK 0x03
+#define EDID_BASIC_AUDIO (1 << 6)
+
+/**
+ * Search EDID for CEA extension block.
+ */
+static u8 *drm_find_cea_extension(struct edid *edid)
+{
+ u8 *edid_ext = NULL;
+ int i;
+
+ /* No EDID or EDID extensions */
+ if (edid == NULL || edid->extensions == 0)
+ return NULL;
+
+ /* Find CEA extension */
+ for (i = 0; i < edid->extensions; i++) {
+ edid_ext = (u8 *)edid + EDID_LENGTH * (i + 1);
+ if (edid_ext[0] == CEA_EXT)
+ break;
+ }
+
+ if (i == edid->extensions)
+ return NULL;
+
+ return edid_ext;
+}
+
/**
* drm_detect_hdmi_monitor - detect whether monitor is hdmi.
* @edid: monitor EDID information
@@ -1277,24 +1305,13 @@
*/
bool drm_detect_hdmi_monitor(struct edid *edid)
{
- char *edid_ext = NULL;
+ u8 *edid_ext;
int i, hdmi_id;
int start_offset, end_offset;
bool is_hdmi = false;
- /* No EDID or EDID extensions */
- if (edid == NULL || edid->extensions == 0)
- goto end;
-
- /* Find CEA extension */
- for (i = 0; i < edid->extensions; i++) {
- edid_ext = (char *)edid + EDID_LENGTH * (i + 1);
- /* This block is CEA extension */
- if (edid_ext[0] == 0x02)
- break;
- }
-
- if (i == edid->extensions)
+ edid_ext = drm_find_cea_extension(edid);
+ if (!edid_ext)
goto end;
/* Data block offset in CEA extension block */
@@ -1325,6 +1342,53 @@
EXPORT_SYMBOL(drm_detect_hdmi_monitor);
/**
+ * drm_detect_monitor_audio - check monitor audio capability
+ *
+ * Monitor should have CEA extension block.
+ * If monitor has 'basic audio', but no CEA audio blocks, it's 'basic
+ * audio' only. If there is any audio extension block and supported
+ * audio format, assume at least 'basic audio' support, even if 'basic
+ * audio' is not defined in EDID.
+ *
+ */
+bool drm_detect_monitor_audio(struct edid *edid)
+{
+ u8 *edid_ext;
+ int i, j;
+ bool has_audio = false;
+ int start_offset, end_offset;
+
+ edid_ext = drm_find_cea_extension(edid);
+ if (!edid_ext)
+ goto end;
+
+ has_audio = ((edid_ext[3] & EDID_BASIC_AUDIO) != 0);
+
+ if (has_audio) {
+ DRM_DEBUG_KMS("Monitor has basic audio support\n");
+ goto end;
+ }
+
+ /* Data block offset in CEA extension block */
+ start_offset = 4;
+ end_offset = edid_ext[2];
+
+ for (i = start_offset; i < end_offset;
+ i += ((edid_ext[i] & 0x1f) + 1)) {
+ if ((edid_ext[i] >> 5) == AUDIO_BLOCK) {
+ has_audio = true;
+ for (j = 1; j < (edid_ext[i] & 0x1f); j += 3)
+ DRM_DEBUG_KMS("CEA audio format %d\n",
+ (edid_ext[i + j] >> 3) & 0xf);
+ goto end;
+ }
+ }
+end:
+ return has_audio;
+}
+EXPORT_SYMBOL(drm_detect_monitor_audio);
+
+/**
* drm_add_edid_modes - add modes from EDID data, if available
* @connector: connector we're probing
* @edid: edid data