[U-Boot] [PATCH v2 1/4] nand: Extend nand_(read|write)_skip_bad with *actual and limit parameters

[Scott Wood]

On 02/27/2013 10:49:55 AM, Tom Rini wrote:
> On Tue, Feb 26, 2013 at 10:56:08AM -0500, Tom Rini wrote:
> 
> > We make these two functions take a size_t pointer to how much space
> > was used on NAND to read or write the buffer (when reads/writes  
> happen)
> > so that bad blocks can be accounted for.  We also make them take an
> > loff_t limit on how much data can be read or written.  This means  
> that
> > we can now catch the case of when writing to a partition would  
> exceed
> > the partition size due to bad blocks.  To do this we also need to  
> make
> [snip]
> >  int nand_read_skip_bad(nand_info_t *nand, loff_t offset, size_t  
> *length,
> > -		       u_char *buffer)
> > +		       size_t *actual, loff_t lim, u_char *buffer)
> [snip]
> > +	if (*actual > lim) {
> > +		puts("Size of read exceeds partition or device  
> limit\n");
> > +		*length = 0;
> > +		return -EFBIG;
> > +	}
> 
> The more I look at this and try testing things, I think I shouldn't be
> introducing a change here.  Before you could do:
> nand read ${address} partname-with-badblock
> 
> And it would suceed but bleed into the next partition if it wasn't the
> last one.  So your production system could do "nand read ${address}
> kernel" and be OK.  But with this change, it would fail because  
> reading
> the whole partition is now too large with a bad block (you would need
> partition+(blocksize*number bad blocks).

You wouldn't be quite so OK if it were a write instead.

> So I'm going to put this back to a check simply against requested size
> being greater than lim rather than required size greater than lim  
> (since
> required size exceeds device is still caught).

No, please retain the check.  The other issue is a separate (though  
related) bug, and there's a patch from Harvey Chapman to deal with it.

-Scott