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@xxxxxxxxxx>
Cc: Christian König <christian.koenig@xxxxxxx>
Cc: Thomas Zimmermann <tzimmermann@xxxxxxx>
Cc: Mauro Carvalho Chehab <mchehab@xxxxxxxxxx>
Cc: dri-devel@xxxxxxxxxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
Signed-off-by: Lucas De Marchi <lucas.demarchi@xxxxxxxxx>
Reviewed-by: Mauro Carvalho Chehab <mchehab@xxxxxxxxxx>
Reviewed-by: Matt Atwood <matthew.s.atwood@xxxxxxxxx>
Reviewed-by: Thomas Zimmermann <tzimmermann@xxxxxxx>
--- 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__ */
-- Thomas Zimmermann Graphics Driver Developer SUSE Software Solutions Germany GmbH Maxfeldstr. 5, 90409 Nürnberg, Germany (HRB 36809, AG Nürnberg) Geschäftsführer: Ivo Totev
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