[PATCH v2 00/24] mtd: rawnand: Improve compile-test coverage

[arnd@xxxxxxxx (Arnd Bergmann)]

On Mon, Jul 9, 2018 at 10:09 PM, Boris Brezillon
<boris.brezillon at bootlin.com> wrote:
> Hello,
>
> This is an attempt at adding "depends || COMPILE_TEST" to all NAND
> drivers that have no compile-time dependencies on arch
> features/headers.
>
> This will hopefully help us (NAND/MTD maintainers) in detecting build
> issues earlier. Unfortunately we still have a few drivers that can't
> easily be modified to be arch independent.
>
> I tried to put all patches that only touch the NAND subsystem first,
> so that they can be applied even if other patches are being discussed.
>
> Don't hesitate to point any missing dependencies when compiled with
> COMPILE_TEST. I didn't have any problem when compiling, but that might
> be because the dependencies were already selected.

Looks good to me overall.

> In this v2, I tried to fix all warnings/errors reported by kbuild/0day
> robots. The only remaining ones are those in omap_elm.c which seems to
> do some weird cpu_to_be32() conversions. I guess I could replace those
> by iowrite32be() calls (or just add (__force __u32)), but I don't want
> to risk a regression on this driver, so I'm just leaving it for someone
> else to fix :P.

Agreed, this is definedly very odd code. It looks like the intention
is to write all the bits in reverse order, but four bytes at a time. I'm
fairly sure the current implementation cannot work on big-endian,
in particularly this line:

val = cpu_to_be32(*(u32 *) &ecc[0]) >> 12;

Since shifting a number after the byteswap is not well-defined.
It's probably correct on little-endian, but it's not clear what the
best way would be to write this is an endian-neutral way.

        Arnd