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

[Arunpravin Paneer Selvam <arunpravin.paneerselvam@amd.com>]

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@amd.com>
>>> Assisted-by: Claude:claude-opus-4-8
>>> Cc: Christian König <christian.koenig@amd.com>
>>> Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
>>> Cc: Matthew Auld <matthew.auld@intel.com>
>>> Cc: Matthew Brost <matthew.brost@intel.com>
>>> Signed-off-by: Arunpravin Paneer Selvam <Arunpravin.PaneerSelvam@amd.com>
>>> ---
>>>    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@igalia.com>
> Looks good to me as well, Reviewed-by: Christian König <christian.koenig@amd.com>.
>
> 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
>>