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

[Ville Syrjälä]

On Sun, Apr 07, 2013 at 12:52:57PM +0200, Rafał Miłecki wrote:
> 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.

The function returns an array of SADs with the zeroed SAD as a
terminator. That kind of magic needs clear documentation IMHO.

In fact I think it would be better if you returned the number of 
SADs too, instead of relying on the zero termination. With a
clear "number of SADs" return parameter it's less likely people
would misuse this by accident.

> + */
> +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);

Missing parens -> miscalculated size. Should really be kcalloc().

> +			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];
> +			}

If the EDID has multiple AUDIO_BLOCKs this will leak memory. 'break'
here would avoid that.

> +		}
> +	}
> +
> +	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
> 
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-- 
Ville Syrjälä
syrjala at sci.fi
http://www.sci.fi/~syrjala/