linux-kernel - Re: [PATCH] video: imxfb: always allocate 256 entries for the color map

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Message-ID: <20170109125942.tk6iutwdnzzxysix@pengutronix.de>
Date:   Mon, 9 Jan 2017 13:59:42 +0100
From:   Sascha Hauer <s.hauer@...gutronix.de>
To:     Martin Kaiser <martin@...ser.cx>
Cc:     b.zolnierkie@...sung.com, kernel@...gutronix.de,
        linux-fbdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] video: imxfb: always allocate 256 entries for the color
 map

On Mon, Jan 02, 2017 at 11:24:02PM +0100, Martin Kaiser wrote:
> The current code calculates the number of color map entries as
> 1 << info->var.bits_per_pixel. For 32bpp modes, 1 << 32 is 0 when
> written to an int variable. As a consequence, the subsequent copying
> of the default (non-empty) color map into our newly allocated color map
> fails and imxfb's probe function returns an error.
> 
> On both imx1 and imx21 platforms, the color map is used only for modes
> with <= 8bpp. By allocating 256 entries for the color map, we're on the
> safe side.
> 
> Signed-off-by: Martin Kaiser <martin@...ser.cx>

Acked-by: Sascha Hauer <s.hauer@...gutronix.de>

Sascha

> ---
> Re-sending: corrected a typo in the LKML address, sorry for that.
> 
>  drivers/video/fbdev/imxfb.c |    6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/video/fbdev/imxfb.c b/drivers/video/fbdev/imxfb.c
> index fe0c4ee..1b0faad 100644
> --- a/drivers/video/fbdev/imxfb.c
> +++ b/drivers/video/fbdev/imxfb.c
> @@ -985,7 +985,11 @@ static int imxfb_probe(struct platform_device *pdev)
>  	 */
>  	imxfb_check_var(&info->var, info);
>  
> -	ret = fb_alloc_cmap(&info->cmap, 1 << info->var.bits_per_pixel, 0);
> +	/*
> +	 * For modes > 8bpp, the color map is bypassed.
> +	 * Therefore, 256 entries are enough.
> +	 */
> +	ret = fb_alloc_cmap(&info->cmap, 256, 0);
>  	if (ret < 0)
>  		goto failed_cmap;
>  
> -- 
> 1.7.10.4
> 
> 
> 

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