Messages in this thread | | | Date | Thu, 27 Jan 2022 15:26:43 +0100 | Subject | Re: [PATCH 01/19] dma-buf-map: Add read/write helpers | From | Thomas Zimmermann <> |
| |
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@linaro.org> > Cc: Christian König <christian.koenig@amd.com> > Cc: linux-media@vger.kernel.org > Cc: dri-devel@lists.freedesktop.org > Cc: linaro-mm-sig@lists.linaro.org > Cc: linux-kernel@vger.kernel.org > Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com> > --- > 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 [unhandled content-type:application/pgp-signature] | |