Re: [PATCH v3 2/8] ttm: turn ttm_bo_device.vma_manager into a pointer

["Koenig, Christian" <Christian.Koenig@amd.com>]

Am 08.08.19 um 14:43 schrieb Thomas Hellström (VMware):
> On 8/8/19 2:02 PM, Daniel Vetter wrote:
>> On Thu, Aug 08, 2019 at 12:35:21PM +0200, Gerd Hoffmann wrote:
>>> On Thu, Aug 08, 2019 at 09:48:49AM +0000, Koenig, Christian wrote:
>>>> Am 08.08.19 um 11:36 schrieb Gerd Hoffmann:
>>>>> Rename the embedded struct vma_offset_manager, it is named 
>>>>> _vma_manager
>>>>> now.  ttm_bo_device.vma_manager is a pointer now, pointing to the
>>>>> embedded ttm_bo_device._vma_manager by default.
>>>>>
>>>>> Add ttm_bo_device_init_with_vma_manager() function which allows to
>>>>> initialize ttm with a different vma manager.
>>>> Can't we go down the route of completely removing the vma_manager from
>>>> TTM? ttm_bo_mmap() would get the BO as parameter instead.
>>> It surely makes sense to target that.  This patch can be a first step
>>> into that direction.  It allows gem and ttm to use the same
>>> vma_offset_manager (see patch #3), which in turn makes various gem
>>> functions work on ttm objects (see patch #4 for vram helpers).
>> +1 on cleaning this up for good, at least long-term ...
>>
>>>> That would also make the verify_access callback completely superfluous
>>>> and looks like a good step into the right direction of de-midlayering.
>>> Hmm, right, noticed that too while working on another patch series.
>>> Guess I'll try to merge those two and see where I end up ...
>> ... but if it gets too invasive I'd vote for incremental changes. 
>> Even if
>> we completely rip out the vma/mmap lookup stuff from ttm, we still 
>> need to
>> keep a copy somewhere for vmwgfx. Or would the evil plan be the vmwgfx
>> would use the gem mmap helpers too?
>
> I don't think it would be too invasive. We could simply move 
> ttm_bo_vm_lookup into a vmw_mmap.

Yeah, agree. vmwgfx would just inherit what TTM is currently doing and 
everybody else would start to use the GEM helpers.

Switching the vma_manager to a pointer might be helpful in the middle of 
the patch set, but as stand a lone change that looks like a detour to me.

I suggest to start by adding the bo as parameter to ttm_bo_mmap and 
moving the lockup out of that function.

Christian.

>
> /Thomas
>
>
>
>
>> -Daniel
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>