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From:   Shengjiu Wang <shengjiu.wang@gmail.com>
Date:   Mon, 13 Apr 2020 15:19:08 +0800
Message-ID: <CAA+D8ANUDAfLVJ6NQvtHSV27G4RUoQYEnA3Ym0wH28YCA6bZMg@mail.gmail.com>
Subject: Re: [PATCH v6 5/7] ASoC: fsl_asrc: Move common definition to fsl_asrc_common
To:     Nicolin Chen <nicoleotsuka@gmail.com>
Cc:     Shengjiu Wang <shengjiu.wang@nxp.com>,
        Mark Rutland <mark.rutland@arm.com>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@vger.kernel.org>,
        Linux-ALSA <alsa-devel@alsa-project.org>,
        Timur Tabi <timur@kernel.org>, Xiubo Li <Xiubo.Lee@gmail.com>,
        linuxppc-dev@lists.ozlabs.org, Takashi Iwai <tiwai@suse.com>,
        Liam Girdwood <lgirdwood@gmail.com>,
        Rob Herring <robh+dt@kernel.org>,
        Mark Brown <broonie@kernel.org>,
        Fabio Estevam <festevam@gmail.com>,
        linux-kernel <linux-kernel@vger.kernel.org>
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On Mon, Apr 13, 2020 at 12:31 PM Nicolin Chen <nicoleotsuka@gmail.com> wrot=
e:
>
> On Mon, Apr 13, 2020 at 11:16:31AM +0800, Shengjiu Wang wrote:
> > On Sun, Apr 12, 2020 at 10:08 AM Nicolin Chen <nicoleotsuka@gmail.com> =
wrote:
> > >
> > > On Sat, Apr 11, 2020 at 01:49:43PM +0800, Shengjiu Wang wrote:
> > >
> > > > > > diff --git a/sound/soc/fsl/fsl_asrc_dma.c b/sound/soc/fsl/fsl_a=
src_dma.c
> > > > > > index b15946e03380..5cf0468ce6e3 100644
> > > > > > --- a/sound/soc/fsl/fsl_asrc_dma.c
> > > > > > +++ b/sound/soc/fsl/fsl_asrc_dma.c
> > > > >
> > > > > > @@ -311,11 +311,12 @@ static int fsl_asrc_dma_startup(struct sn=
d_soc_component *component,
> > > > > >               return ret;
> > > > > >       }
> > > > > >
> > > > > > -     pair =3D kzalloc(sizeof(struct fsl_asrc_pair), GFP_KERNEL=
);
> > > > > > +     pair =3D kzalloc(sizeof(struct fsl_asrc_pair) + PAIR_PRIV=
AT_SIZE, GFP_KERNEL);
> > > > >
> > > > > If we only use the PAIR_PRIVATE_SIZE here, maybe we can put the
> > > > > define in this file too, rather than in the header file.
> > > > >
> > > > > And could fit 80 characters:
> > > > >
> > > > > +       pair =3D kzalloc(sizeof(*pair) + PAIR_PRIVAT_SIZE, GFP_KE=
RNEL);
> > >
> > > > I will use a function pointer
> > > >     int (*get_pair_priv_size)(void)
> > >
> > > Since it's the size of pair or cts structure, could be just a
> > > size_t variable?
> >
> > Yes, should be "size_t (*get_pair_priv_size)(void)"
>
> Does it have to be a function? -- how about this:
>
> struct pair {
>         ...
>         size_t private_size;
>         void *private;
> };
>
> probe/or-somewhere() {
>         ...
>         pair->private =3D pair_priv;

we need to know the size of pair_priv before allocate memory.

>         pair->private_size =3D sizeof(*pair_priv);
>         ...
> }

In fsl_asrc_dma_startup, we need to allocate memory for pair and
pair->private=EF=BC=8Cbut we don't know the object, so we don't know the
size of private, so function pointer is better.

best regards
wang shengjiu