Re: [PATCH v3 02/16] iosys-map: Add a few more helpers

[Lucas De Marchi]

On Thu, Feb 17, 2022 at 09:42:08AM +0100, Thomas Zimmermann wrote:
> Hi
>
> Am 16.02.22 um 18:41 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
> > v3:
> >   - Drop kernel.h include as it's not needed anymore
> >
> > Cc: Sumit Semwal <sumit.semwal@xxxxxxxxxx>
> > Cc: Christian König <christian.koenig@xxxxxxx>
> > Cc: Thomas Zimmermann <tzimmermann@xxxxxxx>
> > Cc: Mauro Carvalho Chehab <mchehab@xxxxxxxxxx>
> > Cc: dri-devel@xxxxxxxxxxxxxxxxxxxxx
> > Cc: linux-kernel@xxxxxxxxxxxxxxx
> > Signed-off-by: Lucas De Marchi <lucas.demarchi@xxxxxxxxx>
> > Reviewed-by: Mauro Carvalho Chehab <mchehab@xxxxxxxxxx>
> > Reviewed-by: Matt Atwood <matthew.s.atwood@xxxxxxxxx>
>
> Reviewed-by: Thomas Zimmermann <tzimmermann@xxxxxxx>

Thanks. I applied the first 2 patches to drm-intel-next.

The rest can't be applied as there are conflicts between drm-intel-next
and drm-intel-gt-next. I should have merged the rename to
drm-intel-gt-next since the guc patches need to be applied there.
I guess the rest will have to wait some tree propagation.


Lucas De Marchi