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 fd033ebbdf84c1f731b1935a6e3fbad352a24a0b..c1a26217a5305ee65a07b85fa77e4c15db77436b 100644 (file)
--- a/drivers/gpu/drm/drm_edid.c
+++ b/drivers/gpu/drm/drm_edid.c
@@ -1267,34 +1267,51 @@ add_detailed_modes(struct drm_connector *connector, struct edid *edid,
 }
 
 #define HDMI_IDENTIFIER 0x000C03
+#define AUDIO_BLOCK    0x01
 #define VENDOR_BLOCK    0x03
+#define EDID_BASIC_AUDIO       (1 << 6)
+
 /**
- * drm_detect_hdmi_monitor - detect whether monitor is hdmi.
- * @edid: monitor EDID information
- *
- * Parse the CEA extension according to CEA-861-B.
- * Return true if HDMI, false if not or unknown.
+ * Search EDID for CEA extension block.
  */
-bool drm_detect_hdmi_monitor(struct edid *edid)
+static u8 *drm_find_cea_extension(struct edid *edid)
 {
-       char *edid_ext = NULL;
-       int i, hdmi_id;
-       int start_offset, end_offset;
-       bool is_hdmi = false;
+       u8 *edid_ext = NULL;
+       int i;
 
        /* No EDID or EDID extensions */
        if (edid == NULL || edid->extensions == 0)
-               goto end;
+               return NULL;
 
        /* 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)
+               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
+ *
+ * Parse the CEA extension according to CEA-861-B.
+ * Return true if HDMI, false if not or unknown.
+ */
+bool drm_detect_hdmi_monitor(struct edid *edid)
+{
+       u8 *edid_ext;
+       int i, hdmi_id;
+       int start_offset, end_offset;
+       bool is_hdmi = false;
+
+       edid_ext = drm_find_cea_extension(edid);
+       if (!edid_ext)
                goto end;
 
        /* Data block offset in CEA extension block */
@@ -1324,6 +1341,53 @@ end:
 }
 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

diff --git a/include/drm/drm_crtc.h b/include/drm/drm_crtc.h
index 15c4796fd467f2d145516b78b949b5f80e042823..029aa688e787c4673c12f38919999982a926e5f6 100644 (file)
--- a/include/drm/drm_crtc.h
+++ b/include/drm/drm_crtc.h
@@ -763,6 +763,7 @@ extern int drm_mode_gamma_get_ioctl(struct drm_device *dev,
 extern int drm_mode_gamma_set_ioctl(struct drm_device *dev,
                                    void *data, struct drm_file *file_priv);
 extern bool drm_detect_hdmi_monitor(struct edid *edid);
+extern bool drm_detect_monitor_audio(struct edid *edid);
 extern int drm_mode_page_flip_ioctl(struct drm_device *dev,
                                    void *data, struct drm_file *file_priv);
 extern struct drm_display_mode *drm_cvt_mode(struct drm_device *dev,