[PATCH v5 3/7] drm/edid: Add cea_sad helpers for freq/length

Markus Schneider-Pargmann
2021-10-21T09:28:46Z

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@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