Re: [PATCH v10 04/21] drm/edid: Add cea_sad helpers for freq/length

On Wed, 2022-05-25 at 14:26 +0200, AngeloGioacchino Del Regno wrote:

Il 23/05/22 12:47, Guillaume Ranquet ha scritto:

...

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 Signed-off-by: Guillaume Ranquet granquet@baylibre.com

---

drivers/gpu/drm/drm_edid.c | 74 ++++++++++++++++++++++++++++++++++++++ include/drm/drm_edid.h | 14 ++++++++ 2 files changed, 88 insertions(+)

diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c index 561f53831e29..61ef1b1c972c 100644 --- a/drivers/gpu/drm/drm_edid.c +++ b/drivers/gpu/drm/drm_edid.c @@ -4758,6 +4758,80 @@ 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:

As far as I know, bit 0 is reserved, so HDMI_AUDIO_CODING_TYPE_STREAM should never occur here?

Hello Angelo,

because we do not know whether "HDMI_AUDIO_CODING_TYPE_STREAM" is compressed, we decide to change this function name to drm_cea_sad_is_pcm to prevent misunderstanding. For this, I will drop case HDMI_AUDIO_CODING_TYPE_STREAM

...

• case HDMI_AUDIO_CODING_TYPE_PCM:

• return true;
  

• default:

• return false;
  

• }

+}

Also, I think that implementing a drm_cea_sad_get_compressed_max_bitrate() function should be pretty straightforward... the spec says that this is 8 bits, byte 3 (your byte2) contains the max bitrate divided by 8kHz, so to extract it, you read byte2 and multiply it by 8000Hz.

/**

• drm_cea_sad_get_compressed_max_bitrate - Extract maximum bitrate
• @sad: Pointer to the cea_sad structure
• Extracts the cea_sad byte2 field and returns the maximum bit rate
• of a compressed audio stream.
• Note: This function may only be called for compressed audio.
• Return: Maximum bitrate of compressed audio stream in bit/s or

•     negative number for error
  

*/ int drm_cea_sad_get_compressed_max_bitrate(const struct cea_sad *sad) { if (drm_cea_sad_is_uncompressed(sad)) { DRM_ERROR("Not supported: tried to get max bitrate for uncompressed format: %u\n", sad->format); return -EINVAL; }

return sad->byte2 * 8000; }

After sync with Jitao, we think this function is not correct. refer to table of "Short Audio Descriptor" in [1].

[1]:https://en.wikipedia.org/wiki/Extended_Display_Identification_Data

BRs, Bo-Chen

...

+/**

• • 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 37c420423625..7a939cb95b38 100644 --- a/include/drm/drm_edid.h +++ b/include/drm/drm_edid.h @@ -373,6 +373,18 @@ struct cea_sad { u8 byte2; };

+#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;

@@ -380,6 +392,8 @@ 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);

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