Re: [PATCH] add PCI ROMs to sysfs

[Jon Smirl <jonsmirl@yahoo.com>]

I was computing the length because of the need to copy for the
partially decoded case. I have one card that maps a 40KB ROM with a
512KB window. In that case it makes a 450KB different in the copy size.

The copy case is adding a lot of complexity to the code. We could just
give it the boot and require that partially decoded drivers just turn
the ROM attribute off.

If not, how do I get the size from your algorithm?

--- Matthew Wilcox <willy@debian.org> wrote:

> On Wed, Aug 25, 2004 at 01:06:38PM -0700, Jon Smirl wrote:
> > New version attached fixes this and the function documentation.
> 
> Sorry, I found two more bugs ;-(
> 
> > +unsigned char *
> > +pci_map_rom(struct pci_dev *pdev, size_t *size)
> > +{
> [...]
> > +	/* Standard PCI ROMs start out with these three bytes 55 AA
> size/512 */
> > +	if ((*rom == 0x55) && (*(rom + 1) == 0xAA))
> > +		*size = *(rom + 2) * 512;	/* return true ROM size, not PCI
> window size */
> 
> First, you're dereferencing an ioremapped pointer directly instead of
> using readb() et al.  This is a portability no-no but happens to work
> on x86.
> 
> Second, only images of code type 0 (Intel x86, PC-AT compatible) are
> specified to have length as the third byte.  OpenFirmware, PA-RISC
> and
> EFI may or may not have size as the third byte.  It's also possible
> that there are multiple images in the ROM.  So what you have to do to
> be correct is something like ...
> 
> 	int last_image;
> 	char *image = rom;
> 	do {
> 		char *pds;
> 		if (readb(image) != 0x55)
> 			break;
> 		if (readb(image + 1) != 0xAA)
> 			break;
> 		pds = image + readw(image + 16);
> 		if (readb(pds) != 'P')
> 			break;
> 		if (readb(pds + 1) != 'C')
> 			break;
> 		if (readb(pds + 2) != 'I')
> 			break;
> 		if (readb(pds + 3) != 'R')
> 			break;
> 		last_image = readb(pds + 21) & 0x80;
> 		image += readw(pds + 16) * 512;
> 	} while (!last_image);
> 
> But I'm not sure it's worth it.  I'm inclined to just map the whole
> thing.
> 
> -- 
> "Next the statesmen will invent cheap lies, putting the blame upon 
> the nation that is attacked, and every man will be glad of those
> conscience-soothing falsities, and will diligently study them, and
> refuse
> to examine any refutations of them; and thus he will by and by
> convince 
> himself that the war is just, and will thank God for the better sleep
> 
> he enjoys after this process of grotesque self-deception." -- Mark
> Twain
> 

=====
Jon Smirl
jonsmirl@yahoo.com


		
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