linux-kernel - Re: [PATCH v5 2/6] ASoC: sgtl5000: Improve VAG power and mute control

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Date:   Fri, 19 Jul 2019 07:09:38 +0000
From:   Oleksandr Suvorov <oleksandr.suvorov@...adex.com>
To:     Cezary Rojewski <cezary.rojewski@...el.com>
CC:     Oleksandr Suvorov <oleksandr.suvorov@...adex.com>,
        Fabio Estevam <festevam@...il.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Igor Opaniuk <igor.opaniuk@...adex.com>,
        Marcel Ziswiler <marcel.ziswiler@...adex.com>,
        "alsa-devel@...a-project.org" <alsa-devel@...a-project.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>,
        Jaroslav Kysela <perex@...ex.cz>,
        Sasha Levin <sashal@...nel.org>,
        Mark Brown <broonie@...nel.org>, Takashi Iwai <tiwai@...e.com>,
        Liam Girdwood <lgirdwood@...il.com>
Subject: Re: [PATCH v5 2/6] ASoC: sgtl5000: Improve VAG power and mute control

On Thu, 18 Jul 2019 at 21:49, Cezary Rojewski <cezary.rojewski@...el.com> wrote:
>
> On 2019-07-18 20:42, Cezary Rojewski wrote:
> > On 2019-07-18 11:02, Oleksandr Suvorov wrote:
> >> +enum {
> >> +    HP_POWER_EVENT,
> >> +    DAC_POWER_EVENT,
> >> +    ADC_POWER_EVENT,
> >> +    LAST_POWER_EVENT
> >> +};
> >> +
> >> +static u16 mute_mask[] = {
> >> +    SGTL5000_HP_MUTE,
> >> +    SGTL5000_OUTPUTS_MUTE,
> >> +    SGTL5000_OUTPUTS_MUTE
> >> +};
> >
> > If mute_mask[] is only used within common handler, you may consider
> > declaring const array within said handler instead (did not check that
> > myself).
> > Otherwise, simple comment for the second _OUTPUTS_MUTE should suffice -
> > its not self explanatory why you doubled that mask.

Ok, I'll add a comment to explain doubled mask.

> >
> >> +
> >>   /* sgtl5000 private structure in codec */
> >>   struct sgtl5000_priv {
> >>       int sysclk;    /* sysclk rate */
> >> @@ -137,8 +157,109 @@ struct sgtl5000_priv {
> >>       u8 micbias_voltage;
> >>       u8 lrclk_strength;
> >>       u8 sclk_strength;
> >> +    u16 mute_state[LAST_POWER_EVENT];
> >>   };
> >
> > When I spoke of LAST enum constant, I did not really had this specific
> > usage in mind.
> >
> >  From design perspective, _LAST_ does not exist and should never be
> > referred to as "the next option" i.e.: new enum constant.

By its nature, LAST_POWER_EVENT is actually a size of the array, but I
couldn't come up with a better name.

> > That is way preferred usage is:
> > u16 mute_state[ADC_POWER_EVENT+1;
> > -or-
> > u16 mute_state[LAST_POWER_EVENT+1];
> >
> > Maybe I'm just being radical here :)

Maybe :)  I don't like first variant (ADC_POWER_EVENT+1): somewhen in
future, someone can add a new event to this enum and we've got a
possible situation with "out of array indexing".

> >
> > Czarek
>
> Forgive me for double posting. Comment above is targeted towards:
>
>  >> +enum {
>  >> +    HP_POWER_EVENT,
>  >> +    DAC_POWER_EVENT,
>  >> +    ADC_POWER_EVENT,
>  >> +    LAST_POWER_EVENT
>  >> +};
>
> as LAST_POWER_EVENT is not assigned explicitly to ADC_POWER_EVENT and
> thus generates implicit "new option" of value 3.

So will you be happy with the following variant?
...
    ADC_POWER_EVENT,
    LAST_POWER_EVENT =  ADC_POWER_EVENT,
...
   u16 mute_state[LAST_POWER_EVENT+1];
...

-- 
Best regards
Oleksandr Suvorov

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