linux-kernel - Re: [PATCH 7/8] backlight: lm3630a_bl: Remove invalid checks for unsigned int

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Date:   Thu, 25 Jun 2020 10:45:07 +0100
From:   Daniel Thompson <daniel.thompson@...aro.org>
To:     Lee Jones <lee.jones@...aro.org>
Cc:     jingoohan1@...il.com, dri-devel@...ts.freedesktop.org,
        linux-fbdev@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        Daniel Jeong <gshark.jeong@...il.com>,
        LDD MLP <ldd-mlp@...t.ti.com>
Subject: Re: [PATCH 7/8] backlight: lm3630a_bl: Remove invalid checks for
 unsigned int < 0

On Wed, Jun 24, 2020 at 03:57:20PM +0100, Lee Jones wrote:
> unsigned ints 'sources' and 'bank' cannot be less than LM3630A_SINK_0 (0)
> and LM3630A_BANK_0 (0) respecitively, so change the logic to only check
> for thier two possible valid values.
> 
> Fixes W=1 warnings:
> 
>  drivers/video/backlight/lm3630a_bl.c: In function ‘lm3630a_parse_led_sources’:
>  drivers/video/backlight/lm3630a_bl.c:394:18: warning: comparison of unsigned expression < 0 is always false [-Wtype-limits]
>  394 | if (sources[i] < LM3630A_SINK_0 || sources[i] > LM3630A_SINK_1)
>  | ^
>  drivers/video/backlight/lm3630a_bl.c: In function ‘lm3630a_parse_bank’:
>  drivers/video/backlight/lm3630a_bl.c:415:11: warning: comparison of unsigned expression < 0 is always false [-Wtype-limits]
>  415 | if (bank < LM3630A_BANK_0 || bank > LM3630A_BANK_1)
>  | ^
> 
> Cc: <stable@...r.kernel.org>
> Cc: Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
> Cc: Daniel Jeong <gshark.jeong@...il.com>
> Cc: LDD MLP <ldd-mlp@...t.ti.com>
> Signed-off-by: Lee Jones <lee.jones@...aro.org>

Reviewed-by: Daniel Thompson <daniel.thompson@...aro.org>


> ---
>  drivers/video/backlight/lm3630a_bl.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/video/backlight/lm3630a_bl.c b/drivers/video/backlight/lm3630a_bl.c
> index ee320883b7108..e88a2b0e59046 100644
> --- a/drivers/video/backlight/lm3630a_bl.c
> +++ b/drivers/video/backlight/lm3630a_bl.c
> @@ -391,7 +391,7 @@ static int lm3630a_parse_led_sources(struct fwnode_handle *node,
>  		return ret;
>  
>  	for (i = 0; i < num_sources; i++) {
> -		if (sources[i] < LM3630A_SINK_0 || sources[i] > LM3630A_SINK_1)
> +		if (sources[i] != LM3630A_SINK_0 && sources[i] != LM3630A_SINK_1)
>  			return -EINVAL;
>  
>  		ret |= BIT(sources[i]);
> @@ -412,7 +412,7 @@ static int lm3630a_parse_bank(struct lm3630a_platform_data *pdata,
>  	if (ret)
>  		return ret;
>  
> -	if (bank < LM3630A_BANK_0 || bank > LM3630A_BANK_1)
> +	if (bank != LM3630A_BANK_0 && bank != LM3630A_BANK_1)
>  		return -EINVAL;
>  
>  	led_sources = lm3630a_parse_led_sources(node, BIT(bank));
> -- 
> 2.25.1
>