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

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Date:   Wed, 4 Jan 2023 07:33:57 -0600
From:   Alex Elder <elder@...e.org>
To:     Deepak R Varma <drv@...lo.com>, 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
Cc:     Saurabh Singh Sengar <ssengar@...rosoft.com>,
        Praveen Kumar <kumarpraveen@...ux.microsoft.com>
Subject: Re: [PATCH] staging: greybus: Replace zero-length array by
 DECLARE_FLEX_ARRAY() helper

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/

> [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.

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

Looks good to me.

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
> 
> 
>