On Wed, Feb 09, 2022 at 07:23:04AM +0100, Thomas Zimmermann wrote:
Hi
Am 08.02.22 um 11:45 schrieb Lucas De Marchi:
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@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
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>
Alphabetically sorted, please.
What requires kernel.h? Can this be reduced to another include statement? Maybe stddef.h for offsetof() ?
Humn... I believe it was something in the previous implementation that is not there anymore. Because this builds fine without the include now and I don't think it is something being included by the headers already here. So this additional include can just be removed.
Lucas De Marchi