linux-kernel - Re: [PATCH] staging: greybus: Replace zero-length array by DECLARE_FLEX

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Date:   Wed, 4 Jan 2023 20:32:35 +0530
From:   Deepak R Varma <drv@...lo.com>
To:     Alex Elder <elder@...e.org>
Cc:     Johan Hovold <johan@...nel.org>, Alex Elder <elder@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        greybus-dev@...ts.linaro.org, linux-staging@...ts.linux.dev,
        linux-kernel@...r.kernel.org,
        Saurabh Singh Sengar <ssengar@...rosoft.com>,
        Praveen Kumar <kumarpraveen@...ux.microsoft.com>,
        Deepak R Varma <drv@...lo.com>
Subject: Re: [PATCH] staging: greybus: Replace zero-length array by
 DECLARE_FLEX_ARRAY() helper

On Wed, Jan 04, 2023 at 07:33:57AM -0600, Alex Elder wrote:
> On 1/3/23 9:57 PM, Deepak R Varma wrote:
> > The code currently uses C90 standard extension based zero length array
> > struct which is now deprecated and the new C99 standard extension of
> > flexible array declarations are to be used instead. Also, the macro
> > DECLARE_FLEX_ARRAY() allows to use single flexible array member in a
> > structure. Refer to these links [1], [2] for details.
>
> Thank you for citing some references in your commit, it's
> a good and helpful practice.  This might have been another
> helpful one:
>
> https://lore.kernel.org/lkml/20210827163015.3141722-2-keescook@chromium.org/

Hello Alex,
Thank you so much for the feedback. I will include the additional reference and
send in a v2.

>
> > [1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html
> > [2] https://lkml.kernel.org/r/YxKY6O2hmdwNh8r8@work
>
> FYI, Linux mailing lists hosted by kernel.org are normally
> cited using "lore.kernel.org" now, e.g.:
>   https://lore.kernel.org/lkml/YxKY6O2hmdwNh8r8@work
> Your patch is fine, this is just so you can consider this
> in the future.

Sure, I will. This is very helpful to know.

>
> > Issue identified using Coccinelle flexible_array.cocci semantic patch.
> >
> > Signed-off-by: Deepak R Varma <drv@...lo.com>
>
> Looks good to me.

Appreciate your time for the review and comments. I will include the reviewed by
tag in my v2.

Regards,
./drv

>
> Reviewed-by: Alex Elder <elder@...aro.org>
>
> > ---
> >   drivers/staging/greybus/usb.c | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/staging/greybus/usb.c b/drivers/staging/greybus/usb.c
> > index 8e9d9d59a357..b7badf87a3f0 100644
> > --- a/drivers/staging/greybus/usb.c
> > +++ b/drivers/staging/greybus/usb.c
> > @@ -27,7 +27,7 @@ struct gb_usb_hub_control_request {
> >   };
> >
> >   struct gb_usb_hub_control_response {
> > -	u8 buf[0];
> > +	DECLARE_FLEX_ARRAY(u8, buf);
> >   };
> >
> >   struct gb_usb_device {
> > --
> > 2.34.1
> >
> >
> >
>