Em Tue, 8 Feb 2022 02:45:08 -0800 Lucas De Marchi <lucas.demarchi@xxxxxxxxx> escreveu: > 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 > > 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> LGTM. Reviewed-by: Mauro Carvalho Chehab <mchehab@xxxxxxxxxx> Regards, Mauro > --- > include/linux/iosys-map.h | 202 ++++++++++++++++++++++++++++++++++++++ > 1 file changed, 202 insertions(+) > > diff --git a/include/linux/iosys-map.h b/include/linux/iosys-map.h > index edd730b1e899..c6b223534b21 100644 > --- a/include/linux/iosys-map.h > +++ b/include/linux/iosys-map.h > @@ -6,6 +6,7 @@ > #ifndef __IOSYS_MAP_H__ > #define __IOSYS_MAP_H__ > > +#include <linux/kernel.h> > #include <linux/io.h> > #include <linux/string.h> > > @@ -120,6 +121,45 @@ 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 +279,26 @@ 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 +315,146 @@ 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__ */ Thanks, Mauro