linux-kernel - Re: [PATCH] greybus: Avoid fake flexible array for response data

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Message-ID: <aDRSaZ4Rq47hjMuY@stanley.mountain>
Date: Mon, 26 May 2025 14:37:13 +0300
From: Dan Carpenter <dan.carpenter@...aro.org>
To: clingfei <clf700383@...il.com>, Kees Cook <keescook@...omium.org>
Cc: elder@...nel.org, johan@...nel.org, vireshk@...nel.org,
	gregkh@...uxfoundation.org, greybus-dev@...ts.linaro.org,
	linux-staging@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] greybus: Avoid fake flexible array for response data

On Mon, May 26, 2025 at 07:06:54PM +0800, clingfei wrote:
> As https://lore.kernel.org/all/20240304211940.it.083-kees@kernel.org/

I don't want to have to read a link to understand the commit message.

Does this change really affect anything in terms of "enforce the 0-sized
destinations" rule?  I don't think this is a destination.  I think Kees
enabled the checking he wanted.  You should probably CC him since we're
refering to his email.

> pointed out, to enforce the 0-sized destinations, the remaining 0-sized
> destinations need to be handled. Thus the struct
> gb_control_get_manifest_response and struct gb_i2c_transfer_response
> are removed.

Here is a better commit message;

"We want to get rid of zero size arrays and use flexible arrays instead.
However, in this case the struct is just one flexible array of u8 which
adds no value.  Just use a char pointer instead."

I would have ignored it, probably but actually the
gb_control_get_manifest_response struct is not used so put that in a
separate commit.  That's a simpler commit to review.

"The gb_control_get_manifest_response struct is not used.  Delete it."

> 
> Signed-off-by: clingfei <clf700383@...il.com>
> ---
>  drivers/staging/greybus/i2c.c             | 9 ++++-----
>  include/linux/greybus/greybus_protocols.h | 9 ---------
>  2 files changed, 4 insertions(+), 14 deletions(-)
> 
> diff --git a/drivers/staging/greybus/i2c.c b/drivers/staging/greybus/i2c.c
> index 14f1ff6d448c..2857c2834206 100644
> --- a/drivers/staging/greybus/i2c.c
> +++ b/drivers/staging/greybus/i2c.c
> @@ -144,15 +144,14 @@ gb_i2c_operation_create(struct gb_connection *connection,
>  }
>  
>  static void gb_i2c_decode_response(struct i2c_msg *msgs, u32 msg_count,
> -				   struct gb_i2c_transfer_response *response)
> +				   u8 *data)
>  {
>  	struct i2c_msg *msg = msgs;
> -	u8 *data;
>  	u32 i;
>  
> -	if (!response)
> +	if (!data)
>  		return;
> -	data = response->data;
> +
>  	for (i = 0; i < msg_count; i++) {
>  		if (msg->flags & I2C_M_RD) {
>  			memcpy(msg->buf, data, msg->len);
> @@ -188,7 +187,7 @@ static int gb_i2c_transfer_operation(struct gb_i2c_device *gb_i2c_dev,
>  
>  	ret = gb_operation_request_send_sync(operation);
>  	if (!ret) {
> -		struct gb_i2c_transfer_response *response;
> +		u8 *response;
>  
>  		response = operation->response->payload;
>  		gb_i2c_decode_response(msgs, msg_count, response);

I like when parameters are called the same thing on both sides.  The
name "response" adds no value.  Instead get rid of that variable and
pass operation->response->payload directly.

		gb_i2c_decode_response(msgs, msg_count,
				       operation->response->payload);

regards,
dan carpenter