| Message ID | 20181130132231.16512-2-hch@lst.de (mailing list archive) |
|---|---|
| State | Not Applicable |
| Headers | show |
| Series | [01/23] dma-mapping: provide a generic DMA_MAPPING_ERROR | expand |
On 30/11/2018 13:22, Christoph Hellwig wrote: > Error handling of the dma_map_single and dma_map_page APIs is a little > problematic at the moment, in that we use different encodings in the > returned dma_addr_t to indicate an error. That means we require an > additional indirect call to figure out if a dma mapping call returned > an error, and a lot of boilerplate code to implement these semantics. > > Instead return the maximum addressable value as the error. As long > as we don't allow mapping single-byte ranges with single-byte alignment > this value can never be a valid return. Additionaly if drivers do > not check the return value from the dma_map* routines this values means > they will generally not be pointed to actual memory. > > Once the default value is added here we can start removing the > various mapping_error methods and just rely on this generic check. > > Signed-off-by: Christoph Hellwig <hch@lst.de> > --- > include/linux/dma-mapping.h | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h > index 0f81c713f6e9..46bd612d929e 100644 > --- a/include/linux/dma-mapping.h > +++ b/include/linux/dma-mapping.h > @@ -133,6 +133,8 @@ struct dma_map_ops { > u64 (*get_required_mask)(struct device *dev); > }; > > +#define DMA_MAPPING_ERROR (~(dma_addr_t)0) > + > extern const struct dma_map_ops dma_direct_ops; > extern const struct dma_map_ops dma_virt_ops; > > @@ -576,6 +578,10 @@ static inline int dma_mapping_error(struct device *dev, dma_addr_t dma_addr) > const struct dma_map_ops *ops = get_dma_ops(dev); > > debug_dma_mapping_error(dev, dma_addr); > + > + if (dma_addr == DMA_MAPPING_ERROR) > + return 1; > + > if (ops->mapping_error) > return ops->mapping_error(dev, dma_addr); > return 0; I'd have been inclined to put the default check here, i.e. - return 0 + return dma_addr == DMA_MAPPING_ERROR such that the callback retains full precedence and we don't have to deal with the non-trivial removals immediately if it comes to it. Not that it makes a vast difference though, so either way, Reviewed-by: Robin Murphy <robin.murphy@arm.com>
On Tue, Dec 04, 2018 at 04:41:34PM +0000, Robin Murphy wrote: > I'd have been inclined to put the default check here, i.e. > > - return 0 > + return dma_addr == DMA_MAPPING_ERROR > > such that the callback retains full precedence and we don't have to deal > with the non-trivial removals immediately if it comes to it. Not that it > makes a vast difference though, so either way, Ok, I've switched it around.
diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h index 0f81c713f6e9..46bd612d929e 100644 --- a/include/linux/dma-mapping.h +++ b/include/linux/dma-mapping.h @@ -133,6 +133,8 @@ struct dma_map_ops { u64 (*get_required_mask)(struct device *dev); }; +#define DMA_MAPPING_ERROR (~(dma_addr_t)0) + extern const struct dma_map_ops dma_direct_ops; extern const struct dma_map_ops dma_virt_ops; @@ -576,6 +578,10 @@ static inline int dma_mapping_error(struct device *dev, dma_addr_t dma_addr) const struct dma_map_ops *ops = get_dma_ops(dev); debug_dma_mapping_error(dev, dma_addr); + + if (dma_addr == DMA_MAPPING_ERROR) + return 1; + if (ops->mapping_error) return ops->mapping_error(dev, dma_addr); return 0;
Error handling of the dma_map_single and dma_map_page APIs is a little problematic at the moment, in that we use different encodings in the returned dma_addr_t to indicate an error. That means we require an additional indirect call to figure out if a dma mapping call returned an error, and a lot of boilerplate code to implement these semantics. Instead return the maximum addressable value as the error. As long as we don't allow mapping single-byte ranges with single-byte alignment this value can never be a valid return. Additionaly if drivers do not check the return value from the dma_map* routines this values means they will generally not be pointed to actual memory. Once the default value is added here we can start removing the various mapping_error methods and just rely on this generic check. Signed-off-by: Christoph Hellwig <hch@lst.de> --- include/linux/dma-mapping.h | 6 ++++++ 1 file changed, 6 insertions(+)