[PATCH 2/7] drm/edid: Allow to ignore the audio EDID data

[Eric Anholt]

Maxime Ripard <maxime.ripard at bootlin.com> writes:

> In some cases, in order to accomodate with displays with poor EDIDs, we
> need to ignore that the monitor alledgedly supports audio output and
> disable the audio output.
>
> Signed-off-by: Maxime Ripard <maxime.ripard at bootlin.com>
> ---
>  drivers/gpu/drm/drm_edid.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
>
> diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
> index 990b1909f9d7..c0258b011bb2 100644
> --- a/drivers/gpu/drm/drm_edid.c
> +++ b/drivers/gpu/drm/drm_edid.c
> @@ -4190,6 +4190,11 @@ bool drm_detect_hdmi_monitor(struct edid *edid)
>  }
>  EXPORT_SYMBOL(drm_detect_hdmi_monitor);
>  
> +static bool ignore_edid_audio = false;
> +module_param(ignore_edid_audio, bool, 0644);
> +MODULE_PARM_DESC(ignore_edid_audio,
> +		 "Ignore the EDID and always consider that a monitor doesn't have audio capabilities");
> +
>  /**
>   * drm_detect_monitor_audio - check monitor audio capability
>   * @edid: EDID block to scan
> @@ -4209,6 +4214,9 @@ bool drm_detect_monitor_audio(struct edid *edid)
>  	bool has_audio = false;
>  	int start_offset, end_offset;
>  
> +	if (ignore_edid_audio)
> +		goto end;
> +
>  	edid_ext = drm_find_cea_extension(edid);
>  	if (!edid_ext)
>  		goto end;

It looks like the motivation for the original flag on Raspberry Pi was
"I've got a non-audio monitor, but the system comes up trying to play
audio to HDMI instead of the analog jack".  Do we have some way for DRM
to communicate to ALSA that this is not the right place to try to play
audio by default?
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