linux-kernel - Re: [PATCH v14 03/10] drm/edid: Add cea

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Message-ID: <f0ba5478d77a5190a9050e4518ebbd44bcd889a6.camel@mediatek.com>
Date:   Thu, 14 Jul 2022 19:19:10 +0800
From:   Rex-BC Chen <rex-bc.chen@...iatek.com>
To:     AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        <chunkuang.hu@...nel.org>, <p.zabel@...gutronix.de>,
        <daniel@...ll.ch>, <robh+dt@...nel.org>,
        <krzysztof.kozlowski+dt@...aro.org>, <mripard@...nel.org>,
        <tzimmermann@...e.de>, <matthias.bgg@...il.com>, <deller@....de>,
        <airlied@...ux.ie>
CC:     <msp@...libre.com>, <granquet@...libre.com>,
        <jitao.shi@...iatek.com>, <wenst@...omium.org>,
        <ck.hu@...iatek.com>, <liangxu.xu@...iatek.com>,
        <dri-devel@...ts.freedesktop.org>,
        <linux-mediatek@...ts.infradead.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-fbdev@...r.kernel.org>,
        <Project_Global_Chrome_Upstream_Group@...iatek.com>
Subject: Re: [PATCH v14 03/10] drm/edid: Add cea_sad helpers for freq/length

On Thu, 2022-07-14 at 13:12 +0200, AngeloGioacchino Del Regno wrote:
> Il 12/07/22 13:12, Bo-Chen Chen ha scritto:
> > From: Guillaume Ranquet <granquet@...libre.com>
> > 
> > This patch adds two helper functions that extract the frequency and
> > word
> > length from a struct cea_sad.
> > 
> > For these helper functions new defines are added that help
> > translate the
> > 'freq' and 'byte2' fields into real numbers.
> > 
> > Signed-off-by: Markus Schneider-Pargmann <msp@...libre.com>
> > Signed-off-by: Guillaume Ranquet <granquet@...libre.com>
> > Signed-off-by: Bo-Chen Chen <rex-bc.chen@...iatek.com>
> > ---
> >   drivers/gpu/drm/drm_edid.c | 73
> > ++++++++++++++++++++++++++++++++++++++
> >   include/drm/drm_edid.h     | 14 ++++++++
> >   2 files changed, 87 insertions(+)
> > 
> > diff --git a/drivers/gpu/drm/drm_edid.c
> > b/drivers/gpu/drm/drm_edid.c
> > index bc43e1b32092..79316d7f1fd8 100644
> > --- a/drivers/gpu/drm/drm_edid.c
> > +++ b/drivers/gpu/drm/drm_edid.c
> > @@ -4916,6 +4916,79 @@ int drm_edid_to_speaker_allocation(const
> > struct edid *edid, u8 **sadb)
> >   }
> >   EXPORT_SYMBOL(drm_edid_to_speaker_allocation);
> >   
> > +/**
> > + * drm_cea_sad_get_sample_rate - Extract the sample rate from
> > cea_sad
> > + * @sad: Pointer to the cea_sad struct
> > + *
> > + * Extracts the cea_sad frequency field and returns the sample
> > rate in Hz.
> > + *
> > + * Return: Sample rate in Hz or a negative errno if parsing
> > failed.
> > + */
> > +int drm_cea_sad_get_sample_rate(const struct cea_sad *sad)
> > +{
> > +	switch (sad->freq) {
> > +	case DRM_CEA_SAD_FREQ_32KHZ:
> > +		return 32000;
> > +	case DRM_CEA_SAD_FREQ_44KHZ:
> > +		return 44100;
> > +	case DRM_CEA_SAD_FREQ_48KHZ:
> > +		return 48000;
> > +	case DRM_CEA_SAD_FREQ_88KHZ:
> > +		return 88200;
> > +	case DRM_CEA_SAD_FREQ_96KHZ:
> > +		return 96000;
> > +	case DRM_CEA_SAD_FREQ_176KHZ:
> > +		return 176400;
> > +	case DRM_CEA_SAD_FREQ_192KHZ:
> > +		return 192000;
> > +	default:
> > +		return -EINVAL;
> > +	}
> > +}
> > +EXPORT_SYMBOL(drm_cea_sad_get_sample_rate);
> > +
> > +static bool drm_cea_sad_is_pcm(const struct cea_sad *sad)
> > +{
> > +	switch (sad->format) {
> > +	case HDMI_AUDIO_CODING_TYPE_PCM:
> > +		return true;
> > +	default:
> > +		return false;
> > +	}
> 
> Are you sure that you need this helper? That's used only in one
> function...
> ...if you really need this one, though, I don't think that using a
> switch
> is the best option here.
> 
> Unless anyone is against that (please, reason?), I would be for doing
> it like:
> 
> 	return sad->format == HDMI_AUDIO_CODING_TYPE_PCM;
> 
> Everything else looks good to me (and working, too).
> 
> Cheers,
> Angelo

Hello Angelo,

I think you are right,
in this case, we don't need this help function.
I will merge this function into
drm_cea_sad_get_uncompressed_word_length()

BRs,
Bo-Chen