linux-kernel - Re: [PATCH v2] ASoC: hdmi-codec: Add option for ELD bypass

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Date:   Sat, 14 May 2022 23:20:45 +0800
From:   sugar zhang <sugar.zhang@...k-chips.com>
To:     Mark Brown <broonie@...nel.org>, Maxime Ripard <maxime@...no.tech>
Cc:     Dmitry Osipenko <digetx@...il.com>,
        Jaroslav Kysela <perex@...ex.cz>,
        Jiapeng Chong <jiapeng.chong@...ux.alibaba.com>,
        Kuninori Morimoto <kuninori.morimoto.gx@...esas.com>,
        Liam Girdwood <lgirdwood@...il.com>,
        Takashi Iwai <tiwai@...e.com>, alsa-devel@...a-project.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] ASoC: hdmi-codec: Add option for ELD bypass

Hi Mark, Maxime,

在 2022/5/4 4:44, Mark Brown 写道:
> On Tue, May 03, 2022 at 10:38:52AM +0200, Maxime Ripard wrote:
>
>> I think some more documentation is needed there to describe how it's
>> going to be used.
>>
>> Like, you mention that it's relevant when the EDID is not valid. But if
>> the EDID is valid, is bypass still allowed or not?
> I'd expect so given that it's explicitly an override and that it's not
> like it's unknown for people to put nonsense in ID information.
>
>>> +static int hdmi_codec_eld_bypass_put(struct snd_kcontrol *kcontrol,
>>> +				     struct snd_ctl_elem_value *ucontrol)
>>> +{
>>> +	struct snd_soc_component *component = snd_kcontrol_chip(kcontrol);
>>> +	struct hdmi_codec_priv *hcp = snd_soc_component_get_drvdata(component);
>>> +
>>> +	if (hcp->eld_bypass == ucontrol->value.integer.value[0])
>>> +		return 0;
>>> +
>>> +	hcp->eld_bypass = ucontrol->value.integer.value[0];
>>> +
>>> +	return 1;
>>> +}
>> If the ELD bypass is set, how does it affect the hdmi_codec_params being
>> passed to the codec?
> Presumably we should tell the CODEC what we're trying to play (looks
> like that's what the current code does)?
>
>> Also, what is being returned to the userspace by hdmi_eld_ctl_get once
>> the bypass is enabled?
> My first thought would be that we'd always read whatever is there
> rather than trying to make something up, bypass just says we're not
> enforcing it.
>
>> And shouldn't we call get_eld when we remove the bypass?
> Or given what I just said above should we not change any get_eld() calls
> but instead only change things so that we don't look at the ELD data
> when setting constraints during startup() and during channel map
> operations?  In that case we wouldn't need to read again.

I agree this idea that just don't use it for constraints and channel map 
or something else.

but still do get_eld() as it was. will do in v3.


-- 
Best Regards!
张学广/Sugar
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