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

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Message-ID: <67b3a842-66aa-2336-3955-d5aa760cdd4b@collabora.com>
Date:   Thu, 14 Jul 2022 13:12:43 +0200
From:   AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>
To:     Bo-Chen Chen <rex-bc.chen@...iatek.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

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