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authorLucas De Marchi <lucas.demarchi@intel.com>2022-02-16 20:41:33 +0300
committerLucas De Marchi <lucas.demarchi@intel.com>2022-02-20 06:23:53 +0300
commite62f25e8b3cdd29224c27938addba817aedd4b54 (patch)
tree081da2bd26f5e13fe92ac54f0fb33d20d923b2e0 /include/linux/iosys-map.h
parentcccd73d607fee52f35b4b030408fa5f6c21ef503 (diff)
downloadlinux-e62f25e8b3cdd29224c27938addba817aedd4b54.tar.xz
iosys-map: Add a few more helpers
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> Link: https://patchwork.freedesktop.org/patch/msgid/20220216174147.3073235-3-lucas.demarchi@intel.com
Diffstat (limited to 'include/linux/iosys-map.h')
-rw-r--r--include/linux/iosys-map.h201
1 files changed, 201 insertions, 0 deletions
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
@@ -121,6 +121,45 @@ struct iosys_map {
}
/**
+ * 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(&copy, offset_); \
+ copy; \
+})
+
+/**
* iosys_map_set_vaddr - Sets a iosys mapping structure to an address in system memory
* @map: The iosys_map structure
* @vaddr: A system-memory address
@@ -240,6 +279,26 @@ static inline void iosys_map_memcpy_to(struct iosys_map *dst, size_t dst_offset,
}
/**
+ * 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
* @incr: The number of bytes to increment
@@ -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__ */