[PATCH v3 3/6] drm/edid: Add cea_sad helpers for freq/length

[Markus Schneider-Pargmann]

This patch adds two helper functions that extract the frequency and word
length from a struct cea_sad.

For these helper functions new defines are added that help translate the
'freq' and 'byte2' fields into real numbers.

Signed-off-by: Markus Schneider-Pargmann <msp at baylibre.com>
---

Notes:
    Changes v2 -> v3:
    - Add DRM_ prefix to the CEA_SAD defines.
    
    Changes v1 -> v2:
    - Use const struct pointers.
    - Add a check whether the format is actually uncompressed or not.

 drivers/gpu/drm/drm_edid.c | 74 ++++++++++++++++++++++++++++++++++++++
 include/drm/drm_edid.h     | 18 ++++++++--
 2 files changed, 90 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
index 6325877c5fd6..c134803e18db 100644
--- a/drivers/gpu/drm/drm_edid.c
+++ b/drivers/gpu/drm/drm_edid.c
@@ -4666,6 +4666,80 @@ int drm_edid_to_speaker_allocation(struct edid *edid, u8 **sadb)
 }
 EXPORT_SYMBOL(drm_edid_to_speaker_allocation);
 
+/**
+ * drm_cea_sad_get_sample_rate - Extract the sample rate from cea_sad
+ * @sad: Pointer to the cea_sad struct
+ *
+ * Extracts the cea_sad frequency field and returns the sample rate in Hz.
+ *
+ * Return: Sample rate in Hz or a negative errno if parsing failed.
+ */
+int drm_cea_sad_get_sample_rate(const struct cea_sad *sad)
+{
+	switch (sad->freq) {
+	case DRM_CEA_SAD_FREQ_32KHZ:
+		return 32000;
+	case DRM_CEA_SAD_FREQ_44KHZ:
+		return 44100;
+	case DRM_CEA_SAD_FREQ_48KHZ:
+		return 48000;
+	case DRM_CEA_SAD_FREQ_88KHZ:
+		return 88200;
+	case DRM_CEA_SAD_FREQ_96KHZ:
+		return 96000;
+	case DRM_CEA_SAD_FREQ_176KHZ:
+		return 176400;
+	case DRM_CEA_SAD_FREQ_192KHZ:
+		return 192000;
+	default:
+		return -EINVAL;
+	}
+}
+EXPORT_SYMBOL(drm_cea_sad_get_sample_rate);
+
+static bool drm_cea_sad_is_uncompressed(const struct cea_sad *sad)
+{
+	switch (sad->format) {
+	case HDMI_AUDIO_CODING_TYPE_STREAM:
+	case HDMI_AUDIO_CODING_TYPE_PCM:
+		return true;
+	default:
+		return false;
+	}
+}
+
+/**
+ * drm_cea_sad_get_uncompressed_word_length - Extract word length
+ * @sad: Pointer to the cea_sad struct
+ *
+ * Extracts the cea_sad byte2 field and returns the word length for an
+ * uncompressed stream.
+ *
+ * Note: This function may only be called for uncompressed audio.
+ *
+ * Return: Word length in bits or a negative errno if parsing failed.
+ */
+int drm_cea_sad_get_uncompressed_word_length(const struct cea_sad *sad)
+{
+	if (!drm_cea_sad_is_uncompressed(sad)) {
+		DRM_WARN("Unable to get the uncompressed word length for a compressed format: %u\n",
+			 sad->format);
+		return -EINVAL;
+	}
+
+	switch (sad->byte2) {
+	case DRM_CEA_SAD_UNCOMPRESSED_WORD_16BIT:
+		return 16;
+	case DRM_CEA_SAD_UNCOMPRESSED_WORD_20BIT:
+		return 20;
+	case DRM_CEA_SAD_UNCOMPRESSED_WORD_24BIT:
+		return 24;
+	default:
+		return -EINVAL;
+	}
+}
+EXPORT_SYMBOL(drm_cea_sad_get_uncompressed_word_length);
+
 /**
  * drm_av_sync_delay - compute the HDMI/DP sink audio-video sync delay
  * @connector: connector associated with the HDMI/DP sink
diff --git a/include/drm/drm_edid.h b/include/drm/drm_edid.h
index deccfd39e6db..9d75df652b17 100644
--- a/include/drm/drm_edid.h
+++ b/include/drm/drm_edid.h
@@ -361,12 +361,24 @@ struct edid {
 
 /* Short Audio Descriptor */
 struct cea_sad {
-	u8 format;
+	u8 format; /* See HDMI_AUDIO_CODING_TYPE_* */
 	u8 channels; /* max number of channels - 1 */
-	u8 freq;
+	u8 freq; /* See CEA_SAD_FREQ_* */
 	u8 byte2; /* meaning depends on format */
 };
 
+#define DRM_CEA_SAD_FREQ_32KHZ  BIT(0)
+#define DRM_CEA_SAD_FREQ_44KHZ  BIT(1)
+#define DRM_CEA_SAD_FREQ_48KHZ  BIT(2)
+#define DRM_CEA_SAD_FREQ_88KHZ  BIT(3)
+#define DRM_CEA_SAD_FREQ_96KHZ  BIT(4)
+#define DRM_CEA_SAD_FREQ_176KHZ BIT(5)
+#define DRM_CEA_SAD_FREQ_192KHZ BIT(6)
+
+#define DRM_CEA_SAD_UNCOMPRESSED_WORD_16BIT BIT(0)
+#define DRM_CEA_SAD_UNCOMPRESSED_WORD_20BIT BIT(1)
+#define DRM_CEA_SAD_UNCOMPRESSED_WORD_24BIT BIT(2)
+
 struct drm_encoder;
 struct drm_connector;
 struct drm_connector_state;
@@ -374,6 +386,8 @@ struct drm_display_mode;
 
 int drm_edid_to_sad(struct edid *edid, struct cea_sad **sads);
 int drm_edid_to_speaker_allocation(struct edid *edid, u8 **sadb);
+int drm_cea_sad_get_sample_rate(const struct cea_sad *sad);
+int drm_cea_sad_get_uncompressed_word_length(const struct cea_sad *sad);
 int drm_av_sync_delay(struct drm_connector *connector,
 		      const struct drm_display_mode *mode);
 
-- 
2.33.0