On 22/10/2019 13:55, Laurentiu Tudor wrote:
From: Laurentiu Tudor <laurentiu.tu...@nxp.com>
Introduce a new dma map op called dma_addr_to_phys_addr() that converts
a dma address to the physical address backing it up and add wrapper for
it.
I'd really love it if there was a name which could encapsulate that this
is *only* for extreme special cases of constrained descriptors/pagetable
entries/etc. where there's simply no practical way to keep track of a
CPU address alongside the DMA address, and the only option is this
potentially-arbitrarily-complex operation (I mean, on some systems it
may end up taking locks and poking hardware).
Either way it's tricky - much as I don't like adding an interface which
is ripe for drivers to misuse, I also really don't want hacks like
bdf95923086f shoved into other APIs to compensate, so on balance I'd
probably consider this proposal ever so slightly the lesser evil.
Signed-off-by: Laurentiu Tudor <laurentiu.tu...@nxp.com>
---
include/linux/dma-mapping.h | 21 +++++++++++++++++++++
1 file changed, 21 insertions(+)
diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
index 4a1c4fca475a..5965d159c9a9 100644
--- a/include/linux/dma-mapping.h
+++ b/include/linux/dma-mapping.h
@@ -132,6 +132,8 @@ struct dma_map_ops {
u64 (*get_required_mask)(struct device *dev);
size_t (*max_mapping_size)(struct device *dev);
unsigned long (*get_merge_boundary)(struct device *dev);
+ phys_addr_t (*dma_addr_to_phys_addr)(struct device *dev,
+ dma_addr_t dma_handle);
I'd be inclined to name the internal callback something a bit snappier
like .get_phys_addr.
};
#define DMA_MAPPING_ERROR (~(dma_addr_t)0)
@@ -442,6 +444,19 @@ static inline int dma_mapping_error(struct device *dev,
dma_addr_t dma_addr)
return 0;
}
+static inline phys_addr_t dma_addr_to_phys_addr(struct device *dev,
+ dma_addr_t dma_handle)
+{
+ const struct dma_map_ops *ops = get_dma_ops(dev);
+
+ if (dma_is_direct(ops))
+ return (phys_addr_t)dma_handle;
Well that's not right, is it - remember why you had that namespace
collision? ;)
Robin.
+ else if (ops->dma_addr_to_phys_addr)
+ return ops->dma_addr_to_phys_addr(dev, dma_handle);
+
+ return 0;
+}
+
void *dma_alloc_attrs(struct device *dev, size_t size, dma_addr_t *dma_handle,
gfp_t flag, unsigned long attrs);
void dma_free_attrs(struct device *dev, size_t size, void *cpu_addr,
@@ -578,6 +593,12 @@ static inline unsigned long dma_get_merge_boundary(struct
device *dev)
{
return 0;
}
+
+static inline phys_addr_t dma_addr_to_phys_addr(struct device *dev,
+ dma_addr_t dma_handle)
+{
+ return 0;
+}
#endif /* CONFIG_HAS_DMA */
static inline dma_addr_t dma_map_single_attrs(struct device *dev, void *ptr,
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