Re: [PATCH] dma-mapping: remove an unnecessary NULL check

[Ian Abbott]

On 24/04/2019 15:27, Christoph Hellwig wrote:
> On Wed, Apr 24, 2019 at 05:24:37PM +0300, Dan Carpenter wrote:
> > We already dereferenced "dev" when we called get_dma_ops() so this NULL
> > check is too late.  We're not supposed to pass NULL "dev" pointers to
> > dma_alloc_attrs().
>
> Thanks, applied to the dma-mapping for-next tree.
>
> > Signed-off-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
> > ---
> > There are still at least two drivers which do pass a NULL unfortunately.
> >
> > drivers/staging/comedi/drivers/comedi_isadma.c:195 comedi_isadma_alloc() error: NULL dereference inside function 'dma_alloc_coherent()'
> > drivers/staging/comedi/drivers/comedi_isadma.c:227 comedi_isadma_free() error: NULL dereference inside function 'dma_free_coherent()'
>
> This is staging code.  Per official decree from Linus we can just
> ignore it, and I tend to do so to keep my sanity.

So for comedi_isadma, we can just replace the NULL with a pointer to a 
static dummy device with a 24-bit coherent mask?

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