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

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Message-id: <2846203.pYN6Pvhiy7@amdc3058>
Date:   Wed, 11 Jan 2017 15:29:49 +0100
From:   Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
To:     Sascha Hauer <s.hauer@...gutronix.de>,
        Martin Kaiser <martin@...ser.cx>
Cc:     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


Hi,

On Monday, January 09, 2017 01:59:42 PM Sascha Hauer wrote:
> 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>

Thanks, patch queued for 4.11.

Best regards,
--
Bartlomiej Zolnierkiewicz
Samsung R&D Institute Poland
Samsung Electronics

> 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;