[PATCH 1/3] drm/edid: add a helper function to extract the speaker allocation data block (v2)

[Ville Syrjälä]

On Wed, Aug 14, 2013 at 12:08:13PM -0400, Alex Deucher wrote:
> This adds a helper function to extract the speaker allocation
> data block from the EDID.  This data block describes what speakers
> are present on the display device.
> 
> v2: update per Ville Syrjälä's comments
> 
> Signed-off-by: Alex Deucher <alexander.deucher at amd.com>
> ---
>  drivers/gpu/drm/drm_edid.c | 52 ++++++++++++++++++++++++++++++++++++++++++++++
>  include/drm/drm_edid.h     |  1 +
>  2 files changed, 53 insertions(+)
> 
> diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
> index 70fc133..2e36d28 100644
> --- a/drivers/gpu/drm/drm_edid.c
> +++ b/drivers/gpu/drm/drm_edid.c
> @@ -2735,6 +2735,58 @@ int drm_edid_to_sad(struct edid *edid, struct cea_sad **sads)
>  EXPORT_SYMBOL(drm_edid_to_sad);
>  
>  /**
> + * drm_edid_to_speaker_allocation - extracts Speaker Allocation Data Blocks from EDID
> + * @edid: EDID to parse
> + * @sadb: pointer to the speaker block
> + *
> + * Looks for CEA EDID block and extracts the Speaker Allocation Data Block from it.
> + * Note: returned pointer needs to be kfreed
> + *
> + * Return number of found Speaker Allocation Blocks or negative number on error.
> + */
> +int drm_edid_to_speaker_allocation(struct edid *edid, u8 **sadb)
> +{
> +	int count = 0;
> +	int i, start, end, dbl;
> +	const u8 *cea;
> +
> +	cea = drm_find_cea_extension(edid);
> +	if (!cea) {
> +		DRM_DEBUG_KMS("SAD: no CEA Extension found\n");
> +		return -ENOENT;
> +	}
> +
> +	if (cea_revision(cea) < 3) {
> +		DRM_DEBUG_KMS("SAD: wrong CEA revision\n");
> +		return -ENOTSUPP;
> +	}
> +
> +	if (cea_db_offsets(cea, &start, &end)) {
> +		DRM_DEBUG_KMS("SAD: invalid data block offsets\n");
> +		return -EPROTO;
> +	}
> +
> +	for_each_cea_db(cea, i, start, end) {
> +		const u8 *db = &cea[i];
> +
> +		if (cea_db_tag(db) == SPEAKER_BLOCK) {
> +			dbl = cea_db_payload_len(db);
> +
> +			/* Speaker Allocation Data Block */
> +			if (dbl == 3) {
> +				*sadb = kcalloc(count, dbl, GFP_KERNEL);

'count' not initialized yet. I suppose it was supposed to be just
kmalloc(dbl, GFP_KERNEL). But since it's just three bytes, making
the user just pass in a pointer to u32 would work just as well
w/o requiring the dynamic alloc/free.

> +				memcpy(*sadb, &db[1], dbl);
> +				count = dbl;
> +				break;
> +			}
> +		}
> +	}
> +
> +	return count;
> +}
> +EXPORT_SYMBOL(drm_edid_to_speaker_allocation);
> +
> +/**
>   * 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 fc481fc..c76a129 100644
> --- a/include/drm/drm_edid.h
> +++ b/include/drm/drm_edid.h
> @@ -259,6 +259,7 @@ struct hdmi_avi_infoframe;
>  
>  void drm_edid_to_eld(struct drm_connector *connector, struct edid *edid);
>  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_av_sync_delay(struct drm_connector *connector,
>  		      struct drm_display_mode *mode);
>  struct drm_connector *drm_select_eld(struct drm_encoder *encoder,
> -- 
> 1.8.3.1
> 
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-- 
Ville Syrjälä
Intel OTC