Re: [PATCH v8 5/6] drm/panthor: Support sparse mappings

[Boris Brezillon]

On Tue, 21 Apr 2026 22:44:18 +0100
Adrián Larumbe <adrian.larumbe@xxxxxxxxxxxxx> wrote:

> >
> > Also, how about we do a
> >
> > 			gem = drm_gem_object_get(&vm->dummy->base)  
> 
> I'm afraid drm_gem_object_get() doesn't return a pointer to the same object. Other drivers work around this
> by defining their own refcnt macro like:
> 
> static inline struct xe_bo *xe_bo_get(struct xe_bo *bo)
> {
> 	if (bo)
> 		drm_gem_object_get(&bo->ttm.base);
> 
> 	return bo;
> }
> 
> However, this is meant to operate on the driver-specific bo rather than a generic DRM one. We could also do this:
> 
> if (!(op->flags & DRM_PANTHOR_VM_BIND_OP_MAP_SPARSE))
>         gem = drm_gem_object_lookup(file, op->bo_handle);
> else
>         drm_gem_object_get(gem = &vm->dummy->base);

If it's just this single instance, let's go for:

	if (!(op->flags & DRM_PANTHOR_VM_BIND_OP_MAP_SPARSE)) {
		gem = drm_gem_object_lookup(file, op->bo_handle);
	} else {
		gem = &vm->dummy->base;
		drm_gem_object_get(gem);
	}

If there are multiple places where we want to acquire a
panthor_gem_object ref, it might make sense to add those
panthor_bo_{get,put}() helpers.