[RFC][PATCH] drm: add helper extracting SADs from EDID

["Rafał Miłecki" <zajec5@gmail.com>]

Some devices (ATI/AMD cards) don't want passing ELD struct to the
hardware but just require filling specific registers and then
hardware/firmware does the rest. In such a cases we need to read info
from SAD blocks and put them in the correct registers.
---
 drivers/gpu/drm/drm_edid.c |   55 ++++++++++++++++++++++++++++++++++++++++++++
 include/drm/drm_edid.h     |   24 +++++++++++++++++++
 2 files changed, 79 insertions(+)

diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
index e2acfdb..7c9e799 100644
--- a/drivers/gpu/drm/drm_edid.c
+++ b/drivers/gpu/drm/drm_edid.c
@@ -2511,6 +2511,61 @@ void drm_edid_to_eld(struct drm_connector *connector, struct edid *edid)
 EXPORT_SYMBOL(drm_edid_to_eld);
 
 /**
+ * drm_edid_to_sad - extracts SADs from EDID
+ * @edid: EDID to parse
+ *
+ * Looks for CEA EDID block and extracts SADs (Short Audio Descriptors) from it.
+ */
+struct cea_sad *drm_edid_to_sad(struct edid *edid)
+{
+	struct cea_sad *sads = NULL;
+	int i, start, end, dbl;
+	u8 *db, *cea;
+
+	cea = drm_find_cea_extension(edid);
+	if (!cea) {
+		DRM_DEBUG_KMS("SAD: no CEA Extension found\n");
+		return NULL;
+	}
+
+	if (cea_revision(cea) < 3) {
+		DRM_DEBUG_KMS("SAD: wrong CEA revision\n");
+		return NULL;
+	}
+
+	if (cea_db_offsets(cea, &start, &end)) {
+		DRM_DEBUG_KMS("SAD: invalid data block offsets\n");
+		return NULL;
+	}
+
+	for_each_cea_db(cea, i, start, end) {
+		db = &cea[i];
+		dbl = cea_db_payload_len(db);
+
+		if (cea_db_tag(db) == AUDIO_BLOCK) {
+			int count = dbl / 3; /* SAD is 3B */
+			int j;
+
+			sads = kzalloc(count + 1 * sizeof(*sads), GFP_KERNEL);
+			if (!sads)
+				return NULL;
+
+			for (j = 0; j < count; j++) {
+				u8 *sad = &db[1 + j * 3];
+
+				sads[j].format = (sad[0] & 0x78) >> 3;
+				sads[j].channels = sad[0] & 0x7;
+				sads[j].freq = sad[1] & 0x7F;
+				sads[j].byte2 = sad[2];
+			}
+		}
+	}
+
+	return sads;
+}
+EXPORT_SYMBOL(drm_edid_to_sad);
+
+/**
  * drm_av_sync_delay - HDMI/DP sink audio-video sync delay in millisecond
  * @connector: connector associated with the HDMI/DP sink
  * @mode: the display mode
diff --git a/include/drm/drm_edid.h b/include/drm/drm_edid.h
index 5da1b4a..b36d052 100644
--- a/include/drm/drm_edid.h
+++ b/include/drm/drm_edid.h
@@ -244,12 +244,36 @@ struct edid {
 
 #define EDID_PRODUCT_ID(e) ((e)->prod_code[0] | ((e)->prod_code[1] << 8))
 
+#define SAD_FORMAT_LPCM			0x01
+#define SAD_FORMAT_AC3			0x02
+#define SAD_FORMAT_MPEG1		0x03
+#define SAD_FORMAT_MP3			0x04
+#define SAD_FORMAT_MPEG2		0x05
+#define SAD_FORMAT_AAC			0x06
+#define SAD_FORMAT_DTS			0x07
+#define SAD_FORMAT_ATRAC		0x08
+#define SAD_FORMAT_ONE_BIT_AUDIO	0x09
+#define SAD_FORMAT_DOLBY_DIGITAL	0x0a
+#define SAD_FORMAT_DTS_HD		0x0b
+#define SAD_FORMAT_MAT_MLP		0x0c
+#define SAD_FORMAT_DST			0x0d
+#define SAD_FORMAT_WMA_PRO		0x0e
+
+/* Short Audio Descriptor */
+struct cea_sad {
+	u8 format;
+	u8 channels; /* max number of channels - 1 */
+	u8 freq;
+	u8 byte2; /* meaning depends on format */
+};
+
 struct drm_encoder;
 struct drm_connector;
 struct drm_display_mode;
 struct hdmi_avi_infoframe;
 
 void drm_edid_to_eld(struct drm_connector *connector, struct edid *edid);
+struct cea_sad *drm_edid_to_sad(struct edid *edid);
 int drm_av_sync_delay(struct drm_connector *connector,
 		      struct drm_display_mode *mode);
 struct drm_connector *drm_select_eld(struct drm_encoder *encoder,
-- 
1.7.10.4