linux-kernel - RE: [EXT] Re: [PATCH 1/3] ASoC: fsl_asrc: Use in(out)put_format instead of in(out)put_word

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Message-ID: <VE1PR04MB6479D271F4271ECF404473E7E3B60@VE1PR04MB6479.eurprd04.prod.outlook.com>
Date:   Tue, 10 Sep 2019 02:22:06 +0000
From:   "S.j. Wang" <shengjiu.wang@....com>
To:     Nicolin Chen <nicoleotsuka@...il.com>
CC:     "timur@...nel.org" <timur@...nel.org>,
        "Xiubo.Lee@...il.com" <Xiubo.Lee@...il.com>,
        "festevam@...il.com" <festevam@...il.com>,
        "lgirdwood@...il.com" <lgirdwood@...il.com>,
        "broonie@...nel.org" <broonie@...nel.org>,
        "perex@...ex.cz" <perex@...ex.cz>,
        "tiwai@...e.com" <tiwai@...e.com>,
        "alsa-devel@...a-project.org" <alsa-devel@...a-project.org>,
        "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [EXT] Re: [PATCH 1/3] ASoC: fsl_asrc: Use in(out)put_format
 instead of in(out)put_word_width

Hi

> 
> On Mon, Sep 09, 2019 at 06:33:19PM -0400, Shengjiu Wang wrote:
> > snd_pcm_format_t is more formal than enum asrc_word_width, which
> has
> > two property, width and physical width, which is more accurate than
> > enum asrc_word_width. So it is better to use in(out)put_format instead
> > of in(out)put_word_width.
> 
> Hmm...I don't really see the benefit of using snd_pcm_format_t here...I
> mean, I know it's a generic one, and would understand if we use it as a
> param for a common API. But this patch merely packs the "width" by
> intentionally using this snd_pcm_format_t and then adds another
> translation to unpack it.. I feel it's a bit overcomplicated. Or am I missing
> something?
> 
> And I feel it's not necessary to use ALSA common format in our own "struct
> asrc_config" since it is more IP/register specific.
> 
> Thanks
> Nicolin
> 

As you know, we have another M2M function internally, when user want to
Set the format through M2M API, it is better to use snd_pcm_format_t instead the
Width, for snd_pcm_format_t include two property, data with and physical width
In driver some place need data width, some place need physical width.
For example how to distinguish S24_LE and S24_3LE in driver,  DMA setting needs
The physical width,  but ASRC need data width. 

Another purpose is that we have another new designed ASRC, which support more
Formats, I would like it can share same API with this ASRC, using snd_pcm_format_t
That we can use the common API, like snd_pcm_format_linear,
snd_pcm_format_big_endian to get the property of the format, which is needed by
driver.


Best regards
Wang shengjiu