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

["Christian König" <christian.koenig@amd.com>]

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.

Thanks,
Christian.

> 
> Regards,
> 
> Tvrtko
>