Re: [PATCH] scsi: debug: fix type mismatch warning for sg_pcopy_from_buffer

[Andrew Morton <akpm@linux-foundation.org>]

On Tue, 19 May 2015 23:22:39 +0200 Arnd Bergmann <arnd@arndb.de> wrote:

> The recent change to mark the input argument of sg_pcopy_from_buffer
> had the unfortunate side-effect to cause a new warning in the
> scsi_debug code:
> 
> drivers/scsi/scsi_debug.c: In function 'do_device_access':
> drivers/scsi/scsi_debug.c:2376:8: warning: assignment from incompatible pointer type [-Wincompatible-pointer-types]
>    func = sg_pcopy_from_buffer;
> 
> This patch attempts to avoid that warning without adding
> evil type casts, but unfortunately makes the do_device_access
> function a lot uglier in the process.
> 
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> Fixes: 5250326459 ("lib/scatterlist: mark input buffer parameters as 'const'")
> ---
> 
> I can't decide if this is actually a good idea, or if we should rather drop
> the sg_pcopy_from_buffer() patch. Maybe someone else sees a better solution.

Could make do_device_access() call sg_copy_buffer() directly.

But yes, dropping the sg_pcopy_from/to_buffer changes is reasonable. 
sg_copy_buffer() is bidirectional and that won't be changing, so
putting constified wrapeprs around it is kinda fake.