Hi Am 26.01.22 um 21:36 schrieb Lucas De Marchi:
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. Add a pair of macros dma_buf_map_read_field()/dma_buf_map_write_field() to calculate the offset of a struct member and memcpy the data from/to the dma_buf_map. 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 on IO memory or dereference the pointer. Cc: Sumit Semwal <sumit.semwal@xxxxxxxxxx> Cc: Christian König <christian.koenig@xxxxxxx> Cc: linux-media@xxxxxxxxxxxxxxx Cc: dri-devel@xxxxxxxxxxxxxxxxxxxxx Cc: linaro-mm-sig@xxxxxxxxxxxxxxxx Cc: linux-kernel@xxxxxxxxxxxxxxx Signed-off-by: Lucas De Marchi <lucas.demarchi@xxxxxxxxx> --- include/linux/dma-buf-map.h | 81 +++++++++++++++++++++++++++++++++++++ 1 file changed, 81 insertions(+) diff --git a/include/linux/dma-buf-map.h b/include/linux/dma-buf-map.h index 19fa0b5ae5ec..65e927d9ce33 100644 --- a/include/linux/dma-buf-map.h +++ b/include/linux/dma-buf-map.h @@ -6,6 +6,7 @@ #ifndef __DMA_BUF_MAP_H__ #define __DMA_BUF_MAP_H__+#include <linux/kernel.h>#include <linux/io.h> #include <linux/string.h>@@ -229,6 +230,46 @@ static inline void dma_buf_map_clear(struct dma_buf_map *map)} }+/**+ * dma_buf_map_memcpy_to_offset - Memcpy into offset of dma-buf mapping + * @dst: The dma-buf mapping structure + * @offset: The offset from which to copy + * @src: The source buffer + * @len: The number of byte in src + * + * Copies data into a dma-buf mapping with an offset. The source buffer is in + * system memory. Depending on the buffer's location, the helper picks the + * correct method of accessing the memory. + */ +static inline void dma_buf_map_memcpy_to_offset(struct dma_buf_map *dst, size_t offset, + const void *src, size_t len) +{ + if (dst->is_iomem) + memcpy_toio(dst->vaddr_iomem + offset, src, len); + else + memcpy(dst->vaddr + offset, src, len); +}
Please don't add a new function. Rather please add the offset parameter to dma_buf_map_memcpy_to() and update the callers. There are only two calls to dma_buf_map_memcpy_to() within the kernel. To make it clear what the offset applies to, I'd call the parameter 'dst_offset'.
+
+/**
+ * dma_buf_map_memcpy_from_offset - Memcpy from offset of dma-buf mapping into system memory
+ * @dst: Destination in system memory
+ * @src: The dma-buf mapping structure
+ * @src: The offset from which to copy
+ * @len: The number of byte in src
+ *
+ * Copies data from a dma-buf mapping 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 dma_buf_map_memcpy_from_offset(void *dst, const struct dma_buf_map *src,
+ size_t offset, size_t len)
+{
+ if (src->is_iomem)
+ memcpy_fromio(dst, src->vaddr_iomem + offset, len);
+ else
+ memcpy(dst, src->vaddr + offset, len);
+}
+
With the dma_buf_map_memcpy_to() changes, please just call this function dma_buf_map_memcpy_from().
/** * 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__)); \ +})
As the original author of this file, I feel like this shouldn't be here. At least not until we have another driver using that pattern.
Best regards Thomas
+ #endif /* __DMA_BUF_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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