Re: [PATCH v2] drm/ttm: add generic drvparam[] alias for ttm_place::fpfn/lpfn

[Arunpravin Paneer Selvam]

On 6/29/2026 5:36 PM, Christian König wrote:
> On 6/26/26 12:57, Tvrtko Ursulin wrote:
> > On 26/06/2026 07:36, Arunpravin Paneer Selvam wrote:
> > > The fpfn/lpfn fields in struct ttm_place are named after page frame
> > > numbers, but they are really just placement parameters interpreted by
> > > the backend resource manager. Wrap them in a union with a generic
> > > drvparam[2] array so backends can access the same storage without the
> > > PFN-specific naming.
> > >
> > > drvparam[0]/drvparam[1] alias fpfn/lpfn, so existing users and the
> > > VRAM range manager are unchanged. This decouples the API from
> > > PFN/range-specific semantics so that these fields can be used more
> > > flexibly in the future (e.g. mask-based or segment-aware placement
> > > constraints). No functional change.
> > >
> > > v2: Use a union exposing a generic drvparam[2] array instead of
> > >       renaming fpfn/lpfn to param1/param2, keeping existing users
> > >       unchanged (Tvrtko Ursulin)
> > >
> > > Suggested-by: Christian König <christian.koenig@xxxxxxx>
> > > Assisted-by: Claude:claude-opus-4-8
> > > Cc: Christian König <christian.koenig@xxxxxxx>
> > > Cc: Thomas Hellström <thomas.hellstrom@xxxxxxxxxxxxxxx>
> > > Cc: Matthew Auld <matthew.auld@xxxxxxxxx>
> > > Cc: Matthew Brost <matthew.brost@xxxxxxxxx>
> > > Signed-off-by: Arunpravin Paneer Selvam <Arunpravin.PaneerSelvam@xxxxxxx>
> > > ---
> > >    include/drm/ttm/ttm_placement.h | 12 ++++++++++--
> > >    1 file changed, 10 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/include/drm/ttm/ttm_placement.h b/include/drm/ttm/ttm_placement.h
> > > index ab2639e42c54..7db2073f3236 100644
> > > --- a/include/drm/ttm/ttm_placement.h
> > > +++ b/include/drm/ttm/ttm_placement.h
> > > @@ -75,14 +75,22 @@
> > >     *
> > >     * @fpfn:    first valid page frame number to put the object
> > >     * @lpfn:    last valid page frame number to put the object
> > > + * @drvparam:    generic driver/backend placement parameters; the
> > > + *        interpretation is defined by the backend resource manager.
> > > + *        drvparam[0] and drvparam[1] alias @fpfn and @lpfn.
> > >     * @mem_type:    One of TTM_PL_* where the resource should be allocated from.
> > >     * @flags:    memory domain and caching flags for the object
> > >     *
> > >     * Structure indicating a possible place to put an object.
> > >     */
> > >    struct ttm_place {
> > > -    uint64_t    fpfn;
> > > -    uint64_t    lpfn;
> > > +    union {
> > > +        struct {
> > > +            uint64_t    fpfn;
> > > +            uint64_t    lpfn;
> > > +        };
> > > +        uint64_t    drvparam[2];
> > > +    };
> > >        uint32_t    mem_type;
> > >        uint32_t    flags;
> > >    };
> > >
> > > base-commit: cdeb2ccd993ed8647adbbda2c3b103aa717fd6f7
> > LGTM but then again I suggested it (hint hint) so I may be biased :)
> >
> > Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxxx>
> Looks good to me as well, Reviewed-by: Christian König <christian.koenig@xxxxxxx>.
>
> I think this way we can also merge it with the AMDGPU patches who needs this through amd-staging-drm-next.
>
> Let's sync up with Alex on the next weekly call, I think we should start creating an internal branch for the new feature if that hasn't be done yet.
Sure Christian.

Thanks,
Arun.
> Thanks,
> Christian.
>
> > Regards,
> >
> > Tvrtko