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SubjectRe: [PATCH] arm64: Use and error-check DMA_ERROR_CODE
On Wed, Oct 01, 2014 at 11:13:23AM +0100, Will Deacon wrote:
> On Tue, Sep 30, 2014 at 09:15:21PM +0100, Sean Paul wrote:
> > This patch replaces the static assignment of ~0 to dma_handle with
> > DMA_ERROR_CODE to be consistent with other platforms.
> >
> > In addition to that, it also adds a check for DMA_ERROR_CODE before
> > calling __dma_free_coherent with an invalid dma_handle.
> >
> > Signed-off-by: Sean Paul <seanpaul@chromium.org>
> > ---
> > arch/arm64/mm/dma-mapping.c | 6 ++++--
> > 1 file changed, 4 insertions(+), 2 deletions(-)
> >
> > diff --git a/arch/arm64/mm/dma-mapping.c b/arch/arm64/mm/dma-mapping.c
> > index 4164c5a..69fd2c4 100644
> > --- a/arch/arm64/mm/dma-mapping.c
> > +++ b/arch/arm64/mm/dma-mapping.c
> > @@ -125,7 +125,7 @@ static void *__dma_alloc_noncoherent(struct device *dev, size_t size,
> > no_map:
> > __dma_free_coherent(dev, size, ptr, *dma_handle, attrs);
> > no_mem:
> > - *dma_handle = ~0;
> > + *dma_handle = DMA_ERROR_CODE;
> > return NULL;
> > }
> >
> > @@ -136,7 +136,9 @@ static void __dma_free_noncoherent(struct device *dev, size_t size,
> > void *swiotlb_addr = phys_to_virt(dma_to_phys(dev, dma_handle));
> >
> > vunmap(vaddr);
> > - __dma_free_coherent(dev, size, swiotlb_addr, dma_handle, attrs);
> > +
> > + if (dma_handle != DMA_ERROR_CODE)
> > + __dma_free_coherent(dev, size, swiotlb_addr, dma_handle, attrs);
>
> Is it legal to try and free a DMA buffer after a failed allocation? If so, I
> think we need something similar for arch/arm/.

If the allocation failed, we don't even have a vaddr to unmap, so I
don't see the reason for the additional check.

--
Catalin


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