linux-kernel - Re: [PATCH v2 01/18] media: i2c: rdamc21: Fix warning on u8 cast

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Message-ID: <0dac151b-35ea-c5e8-8826-661b69ed75dc@ideasonboard.com>
Date:   Mon, 15 Mar 2021 15:27:29 +0000
From:   Kieran Bingham <kieran.bingham+renesas@...asonboard.com>
To:     Jacopo Mondi <jacopo+renesas@...ndi.org>,
        laurent.pinchart+renesas@...asonboard.com,
        niklas.soderlund+renesas@...natech.se, geert@...ux-m68k.org
Cc:     Mauro Carvalho Chehab <mchehab@...nel.org>,
        linux-media@...r.kernel.org, linux-renesas-soc@...r.kernel.org,
        linux-kernel@...r.kernel.org, Hans Verkuil <hverkuil@...all.nl>
Subject: Re: [PATCH v2 01/18] media: i2c: rdamc21: Fix warning on u8 cast

Hi Jacopo,

On 15/03/2021 13:14, Jacopo Mondi wrote:
> Sparse reports a warning on a cast to u8 of a 16 bits constant.
> 
> drivers/media/i2c/rdacm21.c:348:62: warning: cast truncates bits
> from constant value (300a becomes a)
> 
> Even if the behaviour is intended, silence the sparse warning replacing
> the cast with a bitwise & operation.
> 
> Reported-by: Hans Verkuil <hverkuil@...all.nl>
> Signed-off-by: Jacopo Mondi <jacopo+renesas@...ndi.org>

Sounds good to me.

Reviewed-by: Kieran Bingham <kieran.bingham+renesas@...asonboard.com>

> ---
>  drivers/media/i2c/rdacm21.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/media/i2c/rdacm21.c b/drivers/media/i2c/rdacm21.c
> index dcc21515e5a4..179d107f494c 100644
> --- a/drivers/media/i2c/rdacm21.c
> +++ b/drivers/media/i2c/rdacm21.c
> @@ -345,7 +345,7 @@ static int ov10640_initialize(struct rdacm21_device *dev)
>  	/* Read OV10640 ID to test communications. */
>  	ov490_write_reg(dev, OV490_SCCB_SLAVE0_DIR, OV490_SCCB_SLAVE_READ);
>  	ov490_write_reg(dev, OV490_SCCB_SLAVE0_ADDR_HIGH, OV10640_CHIP_ID >> 8);
> -	ov490_write_reg(dev, OV490_SCCB_SLAVE0_ADDR_LOW, (u8)OV10640_CHIP_ID);
> +	ov490_write_reg(dev, OV490_SCCB_SLAVE0_ADDR_LOW, OV10640_CHIP_ID & 0xff);
>  
>  	/* Trigger SCCB slave transaction and give it some time to complete. */
>  	ov490_write_reg(dev, OV490_HOST_CMD, OV490_HOST_CMD_TRIGGER);
>