linux-kernel - Re: [PATCH v3] media: si2168: Refactor command setup code

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Message-ID: <20190712084343.GA28962@taurus.defre.kleine-koenig.org>
Date:   Fri, 12 Jul 2019 10:43:46 +0200
From:   Uwe Kleine-König <uwe@...ine-koenig.org>
To:     Marc Gonzalez <marc.w.gonzalez@...e.fr>
Cc:     Antti Palosaari <crope@....fi>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Jonathan Neuschäfer <j.neuschaefer@....net>,
        linux-media <linux-media@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        MSM <linux-arm-msm@...r.kernel.org>,
        Brad Love <brad@...tdimension.cc>,
        Bjorn Andersson <bjorn.andersson@...aro.org>
Subject: Re: [PATCH v3] media: si2168: Refactor command setup code

Hello,

On Thu, Jul 04, 2019 at 12:33:22PM +0200, Marc Gonzalez wrote:
> Refactor the command setup code, and let the compiler determine
> the size of each command.
> 
> Reviewed-by: Jonathan Neuschäfer <j.neuschaefer@....net>
> Signed-off-by: Marc Gonzalez <marc.w.gonzalez@...e.fr>
> ---
> Changes from v1:
> - Use a real function to populate struct si2168_cmd *cmd, and a trivial
> macro wrapping it (macro because sizeof).
> Changes from v2:
> - Fix header mess
> - Add Jonathan's tag
> ---
>  drivers/media/dvb-frontends/si2168.c | 146 +++++++++------------------
>  1 file changed, 45 insertions(+), 101 deletions(-)
> 
> diff --git a/drivers/media/dvb-frontends/si2168.c b/drivers/media/dvb-frontends/si2168.c
> index c64b360ce6b5..5e81e076369c 100644
> --- a/drivers/media/dvb-frontends/si2168.c
> +++ b/drivers/media/dvb-frontends/si2168.c
> @@ -12,6 +12,16 @@
>  
>  static const struct dvb_frontend_ops si2168_ops;
>  
> +static void cmd_setup(struct si2168_cmd *cmd, char *args, int wlen, int rlen)

I'd add an "inline" here. And you could add a const for *args.

> +{
> +	memcpy(cmd->args, args, wlen);
> +	cmd->wlen = wlen;
> +	cmd->rlen = rlen;
> +}
> +
> +#define CMD_SETUP(cmd, args, rlen) \
> +	cmd_setup(cmd, args, sizeof(args) - 1, rlen)

Here is the chance to add some static checking. Also it is a good habit
to put parens around macro arguments.

Something like:

#define CMD_SETUP(cmd, args, rlen) ({ \
	BUILD_BUG_ON(sizeof((args)) - 1 > SI2168_ARGLEN);
	cmd_setup((cmd), (args), __must_be_array((args)) + sizeof((args)) - 1, (rlen));

Maybe let this macro live in drivers/media/dvb-frontends/si2168_priv.h
where struct si2168_cmd is defined?

I looked over the transformations in the rest of the patch and this
looks good.

Best regards
Uwe

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