Am 27.01.22 um 08:36 schrieb Matthew Brost:
[SNIP]
/**
* dma_buf_map_memcpy_to - Memcpy into dma-buf mapping
* @dst: The dma-buf mapping structure
@@ -263,4 +304,44 @@ static inline void dma_buf_map_incr(struct dma_buf_map *map, size_t incr)
map->vaddr += incr;
}
+/**
+ * dma_buf_map_read_field - Read struct member from dma-buf mapping with
+ * arbitrary size and handling un-aligned accesses
+ *
+ * @map__: The dma-buf mapping structure
+ * @type__: The struct to be used containing the field to read
+ * @field__: Member from struct we want to read
+ *
+ * Read a value from dma-buf mapping calculating the offset and size: this assumes
+ * the dma-buf mapping is aligned with a a struct type__. A single u8, u16, u32
+ * or u64 can be read, based on the offset and size of type__.field__.
+ */
+#define dma_buf_map_read_field(map__, type__, field__) ({ \
+ type__ *t__; \
+ typeof(t__->field__) val__; \
+ dma_buf_map_memcpy_from_offset(&val__, map__, offsetof(type__, field__), \
+ sizeof(t__->field__)); \
+ val__; \
+})
+
+/**
+ * dma_buf_map_write_field - Write struct member to the dma-buf mapping with
+ * arbitrary size and handling un-aligned accesses
+ *
+ * @map__: The dma-buf mapping structure
+ * @type__: The struct to be used containing the field to write
+ * @field__: Member from struct we want to write
+ * @val__: Value to be written
+ *
+ * Write a value to the dma-buf mapping calculating the offset and size.
+ * A single u8, u16, u32 or u64 can be written based on the offset and size of
+ * type__.field__.
+ */
+#define dma_buf_map_write_field(map__, type__, field__, val__) ({ \
+ type__ *t__; \
+ typeof(t__->field__) val____ = val__; \
+ dma_buf_map_memcpy_to_offset(map__, offsetof(type__, field__), \
+ &val____, sizeof(t__->field__)); \
+})
+
Uff well that absolutely looks like overkill to me.
Hold on...
That's a rather special use case as far as I can see and I think we should
only have this in the common framework if more than one driver is using it.
I disagree, this is rather elegant.
The i915 can't be the *only* driver that defines a struct which
describes the layout of a dma_buf object.
That's not the problem, amdgpu as well as nouveau are doing that as
well. The problem is DMA-buf is a buffer sharing framework between drivers.
In other words which importer is supposed to use this with a DMA-buf
exported by another device?
IMO this base macro allows *all* other drivers to build on this write
directly to fields in structures those drivers have defined.
Exactly that's the point. This is something drivers should absolutely
*NOT* do.
That are driver internals and it is extremely questionable to move this
into the common framework.
Regards,
Christian.
Patches
later in this series do this for the GuC ads.
Matt
Regards,
Christian.
#endif /* __DMA_BUF_MAP_H__ */
