Hi
Am 16.02.22 um 18:41 schrieb Lucas De Marchi:
First the simplest ones:
- iosys_map_memset(): when abstracting system and I/O memory, just like the memcpy() use case, memset() also has dedicated functions to be called for using IO memory.
- iosys_map_memcpy_from(): we may need to copy data from I/O memory, not only to.
In certain situations it's useful to be able to read or write to an offset that is calculated by having the memory layout given by a struct declaration. Usually we are going to read/write a u8, u16, u32 or u64.
As a pre-requisite for the implementation, add iosys_map_memcpy_from() to be the equivalent of iosys_map_memcpy_to(), but in the other direction. Then add 2 pairs of macros:
- iosys_map_rd() / iosys_map_wr()
- iosys_map_rd_field() / iosys_map_wr_field()
The first pair takes the C-type and offset to read/write. The second pair uses a struct describing the layout of the mapping in order to calculate the offset and size being read/written.
We could use readb, readw, readl, readq and the write* counterparts, however due to alignment issues this may not work on all architectures. If alignment needs to be checked to call the right function, it's not possible to decide at compile-time which function to call: so just leave the decision to the memcpy function that will do exactly that.
Finally, in order to use the above macros with a map derived from another, add another initializer: IOSYS_MAP_INIT_OFFSET().
v2:
- Rework IOSYS_MAP_INIT_OFFSET() so it doesn't rely on aliasing rules within the union
- Add offset to both iosys_map_rd_field() and iosys_map_wr_field() to allow the struct itself to be at an offset from the mapping
- Add documentation to iosys_map_rd_field() with example and expected memory layout
v3:
- Drop kernel.h include as it's not needed anymore
Cc: Sumit Semwal sumit.semwal@linaro.org Cc: Christian König christian.koenig@amd.com Cc: Thomas Zimmermann tzimmermann@suse.de Cc: Mauro Carvalho Chehab mchehab@kernel.org Cc: dri-devel@lists.freedesktop.org Cc: linux-kernel@vger.kernel.org Signed-off-by: Lucas De Marchi lucas.demarchi@intel.com Reviewed-by: Mauro Carvalho Chehab mchehab@kernel.org Reviewed-by: Matt Atwood matthew.s.atwood@intel.com
Reviewed-by: Thomas Zimmermann tzimmermann@suse.de
include/linux/iosys-map.h | 201 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 201 insertions(+)
diff --git a/include/linux/iosys-map.h b/include/linux/iosys-map.h index edd730b1e899..e69a002d5aa4 100644 --- a/include/linux/iosys-map.h +++ b/include/linux/iosys-map.h @@ -120,6 +120,45 @@ struct iosys_map { .is_iomem = false, \ }
+/**
- IOSYS_MAP_INIT_OFFSET - Initializes struct iosys_map from another iosys_map
- @map_: The dma-buf mapping structure to copy from
- @offset_: Offset to add to the other mapping
- Initializes a new iosys_map struct based on another passed as argument. It
- does a shallow copy of the struct so it's possible to update the back storage
- without changing where the original map points to. It is the equivalent of
- doing:
- .. code-block:: c
- iosys_map map = other_map;
- iosys_map_incr(&map, &offset);
- Example usage:
- .. code-block:: c
- void foo(struct device *dev, struct iosys_map *base_map)
- {
...
struct iosys_map map = IOSYS_MAP_INIT_OFFSET(base_map, FIELD_OFFSET);
...
- }
- The advantage of using the initializer over just increasing the offset with
- iosys_map_incr() like above is that the new map will always point to the
- right place of the buffer during its scope. It reduces the risk of updating
- the wrong part of the buffer and having no compiler warning about that. If
- the assignment to IOSYS_MAP_INIT_OFFSET() is forgotten, the compiler can warn
- about the use of uninitialized variable.
- */
+#define IOSYS_MAP_INIT_OFFSET(map_, offset_) ({ \
- struct iosys_map copy = *map_; \
- iosys_map_incr(©, offset_); \
- copy; \
+})
- /**
- iosys_map_set_vaddr - Sets a iosys mapping structure to an address in system memory
- @map: The iosys_map structure
@@ -239,6 +278,26 @@ static inline void iosys_map_memcpy_to(struct iosys_map *dst, size_t dst_offset, memcpy(dst->vaddr + dst_offset, src, len); }
+/**
- iosys_map_memcpy_from - Memcpy from iosys_map into system memory
- @dst: Destination in system memory
- @src: The iosys_map structure
- @src_offset: The offset from which to copy
- @len: The number of byte in src
- Copies data from a iosys_map with an offset. The dest buffer is in
- system memory. Depending on the mapping location, the helper picks the
- correct method of accessing the memory.
- */
+static inline void iosys_map_memcpy_from(void *dst, const struct iosys_map *src,
size_t src_offset, size_t len)+{
- if (src->is_iomem)
memcpy_fromio(dst, src->vaddr_iomem + src_offset, len);- else
memcpy(dst, src->vaddr + src_offset, len);+}
- /**
- iosys_map_incr - Increments the address stored in a iosys mapping
- @map: The iosys_map structure
@@ -255,4 +314,146 @@ static inline void iosys_map_incr(struct iosys_map *map, size_t incr) map->vaddr += incr; }
+/**
- iosys_map_memset - Memset iosys_map
- @dst: The iosys_map structure
- @offset: Offset from dst where to start setting value
- @value: The value to set
- @len: The number of bytes to set in dst
- Set value in iosys_map. Depending on the buffer's location, the helper
- picks the correct method of accessing the memory.
- */
+static inline void iosys_map_memset(struct iosys_map *dst, size_t offset,
int value, size_t len)+{
- if (dst->is_iomem)
memset_io(dst->vaddr_iomem + offset, value, len);- else
memset(dst->vaddr + offset, value, len);+}
+/**
- iosys_map_rd - Read a C-type value from the iosys_map
- @map__: The iosys_map structure
- @offset__: The offset from which to read
- @type__: Type of the value being read
- Read a C type value from iosys_map, handling possible un-aligned accesses to
- the mapping.
- Returns:
- The value read from the mapping.
- */
+#define iosys_map_rd(map__, offset__, type__) ({ \
- type__ val; \
- iosys_map_memcpy_from(&val, map__, offset__, sizeof(val)); \
- val; \
+})
+/**
- iosys_map_wr - Write a C-type value to the iosys_map
- @map__: The iosys_map structure
- @offset__: The offset from the mapping to write to
- @type__: Type of the value being written
- @val__: Value to write
- Write a C-type value to the iosys_map, handling possible un-aligned accesses
- to the mapping.
- */
+#define iosys_map_wr(map__, offset__, type__, val__) ({ \
- type__ val = (val__); \
- iosys_map_memcpy_to(map__, offset__, &val, sizeof(val)); \
+})
+/**
- iosys_map_rd_field - Read a member from a struct in the iosys_map
- @map__: The iosys_map structure
- @struct_offset__: Offset from the beggining of the map, where the struct
is located
- @struct_type__: The struct describing the layout of the mapping
- @field__: Member of the struct to read
- Read a value from iosys_map considering its layout is described by a C struct
- starting at @struct_offset__. The field offset and size is calculated and its
- value read handling possible un-aligned memory accesses. For example: suppose
- there is a @struct foo defined as below and the value ``foo.field2.inner2``
- needs to be read from the iosys_map:
- .. code-block:: c
- struct foo {
int field1;
struct {
int inner1;
int inner2;
} field2;
int field3;
- } __packed;
- This is the expected memory layout of a buffer using iosys_map_rd_field():
- +------------------------------+--------------------------+
- | Address | Content |
- +==============================+==========================+
- | buffer + 0000 | start of mmapped buffer |
- | | pointed by iosys_map |
- +------------------------------+--------------------------+
- | ... | ... |
- +------------------------------+--------------------------+
- | buffer + ``struct_offset__`` | start of ``struct foo`` |
- +------------------------------+--------------------------+
- | ... | ... |
- +------------------------------+--------------------------+
- | buffer + wwww | ``foo.field2.inner2`` |
- +------------------------------+--------------------------+
- | ... | ... |
- +------------------------------+--------------------------+
- | buffer + yyyy | end of ``struct foo`` |
- +------------------------------+--------------------------+
- | ... | ... |
- +------------------------------+--------------------------+
- | buffer + zzzz | end of mmaped buffer |
- +------------------------------+--------------------------+
- Values automatically calculated by this macro or not needed are denoted by
- wwww, yyyy and zzzz. This is the code to read that value:
- .. code-block:: c
- x = iosys_map_rd_field(&map, offset, struct foo, field2.inner2);
- Returns:
- The value read from the mapping.
- */
+#define iosys_map_rd_field(map__, struct_offset__, struct_type__, field__) ({ \
- struct_type__ *s; \
- iosys_map_rd(map__, struct_offset__ + offsetof(struct_type__, field__), \
typeof(s->field__)); \+})
+/**
- iosys_map_wr_field - Write to a member of a struct in the iosys_map
- @map__: The iosys_map structure
- @struct_offset__: Offset from the beggining of the map, where the struct
is located
- @struct_type__: The struct describing the layout of the mapping
- @field__: Member of the struct to read
- @val__: Value to write
- Write a value to the iosys_map considering its layout is described by a C struct
- starting at @struct_offset__. The field offset and size is calculated and the
- @val__ is written handling possible un-aligned memory accesses. Refer to
- iosys_map_rd_field() for expected usage and memory layout.
- */
+#define iosys_map_wr_field(map__, struct_offset__, struct_type__, field__, val__) ({ \
- struct_type__ *s; \
- iosys_map_wr(map__, struct_offset__ + offsetof(struct_type__, field__), \
typeof(s->field__), val__); \+})
- #endif /* __IOSYS_MAP_H__ */