Re: [PATCH] jffs2 summary allocation

David Brownell
2008-04-04T23:58:43Z

On Friday 04 April 2008, Josh Boyer wrote:
>
> >   ... This means specifically that you may _not_ use the
> >   memory/addresses returned from vmalloc() for DMA.  ...
> >
> > So I'm rather surprised to see *ANY* kernel code trying to do
> > that.  That rule has been in effect for many, many years now.
>
> I don't think it was intentional.  You're going through several layers
> here:
>
> JFFS2 -> mtd parts -> mtd dataflash -> atmel_spi.
>
> Typically MTD drivers aren't doing DMAs to flash and JFFS2 has no idea
> which particular chip driver is being used because it's abstracted by
> MTD.

That's true ... although I can imagine using DMA to
avoid dcache trashing if its setup cost is low enough,
with either NAND or NOR chips.

Still: in this context vmalloc() is wrong.

- Dave