Hi Am 27.01.22 um 17:34 schrieb Lucas De Marchi:
On Thu, Jan 27, 2022 at 03:26:43PM +0100, Thomas Zimmermann wrote: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.Let me try to clear out the confusion. Then maybe I can extend the documentation of this function in v2 if I'm able to convince this is useful here. This is not about importer/exporter, having this to work cross-driver. This is about using dma_buf_map (which we are talking about on renaming to iosys_map or something else) for inner driver allocations/abstractions. The abstraction added by iosys_map helps on sharing the same functions we had before. And this macro here is very useful when the buffer is described by a struct layout. Example: struct bla { struct inner inner1; struct inner inner2; u32 x, y ,z; }; Functions that would previously do: struct bla *bla = ...; bla->x = 100; bla->y = 200; bla->inner1.inner_inner_field = 30; Can do the below, having the system/IO memory abstracted away (calling it iosys_map here instead of dma_buf_map, hopeful it helps): struct iosys_map *map = ...;
Please don't start renaming anything here. If we want to do this, let's have a separate mail thread for coloring the bike shed.
iosys_map_write_field(map, struct bla, x, 100); iosys_map_write_field(map, struct bla, y, 200); iosys_map_write_field(map, struct bla, inner1.inner_inner_field, 30);
I don't have strong feelings about these macros. They just seemed not needed in general. But I we want to add them here, I 'd like to propose a few small changes.
Again, please add an offset parameter for the map's pointer.Then I'd call them either dma_buf_map_rd/dma_buf_map_wr for read/write OR dma_buf_map_ld/dma_buf_map_st for load/store. They should take a C type. Something like this
dma_buf_map_wr(map, offset, int32, 0x01234); val = dam_buf_map_rd(map, offset, int32);Hopefully, that's flexible enough for all users. On top of that, you can build additional helpers like dma_buf_map_rd_field() and dma_buf_map_wr_field().
Ok? Best regards Thomas
When we are using mostly the same map, the individual drivers can add quick helpers on top. See the ads_blob_write() added in this series, which guarantees the map it's working on is always the guc->ads_map, while reducing verbosity to use the API. From patch "drm/i915/guc: Add read/write helpers for ADS blob": #define ads_blob_read(guc_, field_) \ dma_buf_map_read_field(&(guc_)->ads_map, struct __guc_ads_blob, \ field_) #define ads_blob_write(guc_, field_, val_) \ dma_buf_map_write_field(&(guc_)->ads_map, struct __guc_ads_blob,\ field_, val_) So in intel_guc_ads, we can have a lot of: - bla->x = 100; + ads_blob_write(guc, x, 10); thanks Lucas De Marchi
-- 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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