[U-Boot] [PATCH] fw_env: add NAND support

[Guennadi Liakhovetski]

On Tue, 2 Sep 2008, Wolfgang Denk wrote:

> > +	/* Offset inside a block */
> > +	block_seek = offset - blockstart;
> ...
> > +		/* Limit to one block for the first read */
> 
> Why?

Because this is on NAND, there we have to perform all IO block at a time.

> > +
> > +		/*
> > +		 * If a block is bad, we retry in the next block at the same
> > +		 * offset - see common/env_nand.c::writeenv()
> > +		 */
> > +		lseek (fd, blockstart + block_seek, SEEK_SET);
> 
> Hm... there was a "continue" for the badblock case just above, so do
> we really try the _next_ block here?

I meant, if the first block with non-zero offset (block_seek) was bad, 
then in the _next_ after it block we try at the same offset.

> > +	/*
> > +	 * Data size we actually have to write: from the start of the block
> > +	 * to the start of the data, then count bytes ob data, and to the
> -------------------------------------------------------^ f
> > +	 * end of the block
> > +	 */
> 
> Hm... sounds as if this was always exactly one full block, then?

or two, or three...

> > +	write_total = (block_seek + count + blocklen - 1) & ~(blocklen - 1);
> > +
> > +	/*
> > +	 * Support data anywhere within erase sectors: read out the complete
> > +	 * area to be erased, replace the environment image, write the whole
> > +	 * block back again.
> > +	 */
> > +	if (write_total > count) {
> > +		data = malloc (erase_len);
> 
> My understanding is, that erase_len can be > block size. Is this
> correct?

Yes.

> I don't see where the actual size of the environment data is taken
> into considration?

in the "count" function parameter, which is then used to calculate 
write_total.

> > +	} else {
> > +		/* Offset is block-aligned by construction here */
> 
> What does "block-aligned by construction" mean?

It means, by the way I constructed (calculated) lengths above this place, 
we land here only if offset is block-aligned.

> > +	erase.length = erasesize;
> > +
> > +	/* This only runs once on NOR flash */
> 
> How comes that?

Because on NOR I set "erasesize" to the total length of the data plus 
alignment.

Thanks
Guennadi
---
Guennadi Liakhovetski, Ph.D.

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