linux-kernel - Re: [PATCH] media: renesas: rzg2l-cru: Simplify FIFO empty check

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Message-ID: <20250428095940.GE3371@pendragon.ideasonboard.com>
Date: Mon, 28 Apr 2025 12:59:40 +0300
From: Laurent Pinchart <laurent.pinchart@...asonboard.com>
To: Prabhakar <prabhakar.csengg@...il.com>
Cc: Mauro Carvalho Chehab <mchehab@...nel.org>,
	Hans Verkuil <hverkuil@...all.nl>, linux-media@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-renesas-soc@...r.kernel.org,
	Biju Das <biju.das.jz@...renesas.com>,
	Fabrizio Castro <fabrizio.castro.jz@...esas.com>,
	Tommaso Merciai <tommaso.merciai.xr@...renesas.com>,
	Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>,
	Dan Carpenter <dan.carpenter@...aro.org>
Subject: Re: [PATCH] media: renesas: rzg2l-cru: Simplify FIFO empty check

Hi Prabhakar,

Thank you for the patch.

On Mon, Apr 28, 2025 at 10:52:08AM +0100, Prabhakar wrote:
> From: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
> 
> Simplify the `rzg2l_fifo_empty()` helper by removing the redundant
> comparison in the return path. Now the function explicitly returns `true`
> if the FIFO write and read pointers match, and `false` otherwise, improving
> readability without changing behavior.
> 
> Reported-by: Dan Carpenter <dan.carpenter@...aro.org>
> Closes: https://lore.kernel.org/all/aAtQThCibZCROETx@stanley.mountain/
> Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
> ---
>  drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c b/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c
> index 067c6af14e95..97faefcd6019 100644
> --- a/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c
> +++ b/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c
> @@ -348,7 +348,7 @@ bool rzg2l_fifo_empty(struct rzg2l_cru_dev *cru)
>  	if (amnfifopntr_w == amnfifopntr_r_y)
>  		return true;
>  
> -	return amnfifopntr_w == amnfifopntr_r_y;
> +	return false;

So the function always returned true. This seems to be a bug fix, please
add a Fixes: tag. The commit message should also make it clear that
you're fixing an issue, not just simplifying the code.

Personally I'd have written

diff --git a/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c b/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c
index 067c6af14e95..3d0810b3c35e 100644
--- a/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c
+++ b/drivers/media/platform/renesas/rzg2l-cru/rzg2l-video.c
@@ -345,8 +345,6 @@ bool rzg2l_fifo_empty(struct rzg2l_cru_dev *cru)
 	amnfifopntr_w = amnfifopntr & AMnFIFOPNTR_FIFOWPNTR;
 	amnfifopntr_r_y =
 		(amnfifopntr & AMnFIFOPNTR_FIFORPNTR_Y) >> 16;
-	if (amnfifopntr_w == amnfifopntr_r_y)
-		return true;

 	return amnfifopntr_w == amnfifopntr_r_y;
 }

but that's also a bit of a style preference.

>  }
>  
>  void rzg2l_cru_stop_image_processing(struct rzg2l_cru_dev *cru)

-- 
Regards,

Laurent Pinchart