Re: [PATCH 1/4] video: add fb_edid_add_monspecs for parsing

[Andrew Morton <akpm@linux-foundation.org>]

On Thu, 28 Oct 2010 14:34:44 +0200 (CEST)
Guennadi Liakhovetski <g.liakhovetski@gmx.de> wrote:

> From: Erik Gilling <konkers@android.com>
> 
> Modern monitors/tvs have more extended EDID information blocks which can
> contain extra detailed modes.  This adds a fb_edid_add_monspecs function
> which drivers can use to parse those additions blocks.
> 
> Signed-off-by: Erik Gilling <konkers@android.com>
> ---
>  drivers/video/fbmon.c |   57 +++++++++++++++++++++++++++++++++++++++++++++++++
>  include/linux/fb.h    |    2 +
>  2 files changed, 59 insertions(+), 0 deletions(-)
> 
> diff --git a/drivers/video/fbmon.c b/drivers/video/fbmon.c
> index 563a98b..a0b5a93 100644
> --- a/drivers/video/fbmon.c
> +++ b/drivers/video/fbmon.c
> @@ -973,6 +973,63 @@ void fb_edid_to_monspecs(unsigned char *edid, struct fb_monspecs *specs)
>  	DPRINTK("====================\n");
>  }
>  
> +void fb_edid_add_monspecs(unsigned char *edid, struct fb_monspecs *specs)

Please document it.  This is a general rule when implementing
library-style functions.

> +{
> +	unsigned char *block;
> +	struct fb_videomode *mode, *m;
> +	int num = 0, i, first = 1;
> +
> +	if (edid = NULL)
> +		return;
> +
> +	if (!edid_checksum(edid))
> +		return;
> +
> +	if (edid[0] != 0x2)
> +		return;
> +
> +	mode = kzalloc(50 * sizeof(struct fb_videomode), GFP_KERNEL);
> +	if (mode = NULL)
> +		return;
> +
> +	block = edid + edid[0x2];
> +
> +	DPRINTK("  Extended Detailed Timings\n");
> +
> +	for (i = 0; i < (128 - edid[0x2]) / DETAILED_TIMING_DESCRIPTION_SIZE;

It should validate edid[2] first, methinks.  If it's some crazy value
then this loop will run off into the weeds.

> +	     i++, block += DETAILED_TIMING_DESCRIPTION_SIZE) {
> +		if (!(block[0] = 0x00 && block[1] = 0x00)) {
> +			get_detailed_timing(block, &mode[num]);
> +			if (first) {
> +			        mode[num].flag |= FB_MODE_IS_FIRST;
> +				first = 0;
> +			}
> +			num++;
> +		}
> +	}
> +
> +	/* Yikes, EDID data is totally useless */
> +	if (!num) {
> +		kfree(mode);
> +		return;
> +	}
> +
> +	m = kzalloc((specs->modedb_len + num) *
> +		       sizeof(struct fb_videomode), GFP_KERNEL);
> +
> +	if (!m) {
> +		kfree(mode);
> +		return;
> +	}
> +
> +	memmove(m, specs->modedb, specs->modedb_len * sizeof(struct fb_videomode));
> +	memmove(m + specs->modedb_len, mode, num * sizeof(struct fb_videomode));

It's unusual to use memmove() for a copy which cannot overlap -
memcpy() would be more typical.  memmove() works though.


> +	kfree(mode);
> +	kfree(specs->modedb);
> +	specs->modedb = m;
> +	specs->modedb_len = specs->modedb_len + num;
> +}

Without an EXPORT_SYMBOL(), other modules cannot use this function?

>  /*
>   * VESA Generalized Timing Formula (GTF)
>   */
> diff --git a/include/linux/fb.h b/include/linux/fb.h
> index f0268de..3fc99cb 100644
> --- a/include/linux/fb.h
> +++ b/include/linux/fb.h
> @@ -1086,6 +1086,8 @@ extern int fb_parse_edid(unsigned char *edid, struct fb_var_screeninfo *var);
>  extern const unsigned char *fb_firmware_edid(struct device *device);
>  extern void fb_edid_to_monspecs(unsigned char *edid,
>  				struct fb_monspecs *specs);
> +extern void fb_edid_add_monspecs(unsigned char *edid,
> +				 struct fb_monspecs *specs);
>  extern void fb_destroy_modedb(struct fb_videomode *modedb);
>  extern int fb_find_mode_cvt(struct fb_videomode *mode, int margins, int rb);
>  extern unsigned char *fb_ddc_read(struct i2c_adapter *adapter);
> -- 
> 1.7.1