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

[Guennadi Liakhovetski <g.liakhovetski@gmx.de>]

Hi Andrew

On Thu, 28 Oct 2010, Andrew Morton wrote:

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

Thanks for your comments. My plan is to add my S-o-b to this patch from 
Erik, but otherwise leave it unchanged, because that's what the 2nd patch 
in this series is for - for fixes and improvements. So, I'll address all 
your comments in it, is this ok with you?

Thanks
Guennadi

> > 
> > 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
> 

---
Guennadi Liakhovetski, Ph.D.
Freelance Open-Source Software Developer
http://www.open-technology.de/