Re: [PATCH v2 1/4] dma-mapping: Add devm_ interface for dma_map_single()
From: Eli Billauer
Date: Fri Jun 06 2014 - 12:22:47 EST
On 06/06/14 19:01, Greg KH wrote:
Please try to put yourself in my position: I have a driver that I care
> about, which works fine for a few years. It's based upon dma_map_single(),
> which seems to be the common way to get non-coherent memory, even for the
> driver's entire lifespan. I realize that dma_alloc_* was the intended way to
> do it, but fact is that dma_map_* has become the common choice.
Is your driver in the kernel tree? If not, you really are on your own :(
It's the Xillybus driver in the staging area. I don't know if this
counts for being in the kernel tree...
The suggested patchset would allow replacing my use of dma_map_single()
with a managed version of that function. This will clean the driver's
code considerably.
But I think that the discussion here is if it's valid to use
dma_map_single() for a device-permanent DMA mapping, or if
dma_alloc_noncoherent() is the only way. If the answer is no, there's
quite obviously no point in a devres version for that function.
Regards,
Eli
greg k-h
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