Hello,
On Tue, May 20, 2014 at 08:54:09AM +0300, Eli Billauer wrote:
> That seems OK to me, but the problem I'm concerned with is this: In
> devm_get_free_pages() it says
>
> devres = devres_alloc(devm_pages_release,
> sizeof(struct pages_devres), GFP_KERNEL);
> if (unlikely(!devres)) {
> free_pages(addr, order);
> return 0;
> }
>
> What should I put instead of this "return 0" to conform with the current
> API?
Ah, okay. No idea.
> And to make things even worse, on some architectures, dma_mapping_error()
> always returns success, regardless of dma_handle. So if we stick to the
> current API, the caller of devm_get_free_pages() will never know it failed
> on these architectures.
>
> So my conclusion was that the caller must be aware that if
> devm_get_free_pages() returns zero it's an error, regardless of
> dma_mapping_error(). That breaks the API. Once it's broken, why not return
> zero on all possible errors?
What if 0 is a valid return for the architecture? Isn't that the
whole point of dma_mapping_error() interface? Maybe the right thing
to do is using a separate out argument for dma_handle?
int dmam_map_single(blah blah, dma_addr_t *out_addr);
So that it can return -errno like other non-crazy functions? We'll
probably ask somebody who knows this code better.
Thanks.
--
tejun
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