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Message-ID: <1cee380fb31e1a2f499e50e6b8771d86a68c1b16.camel@imgtec.com>
Date: Wed, 14 Jun 2023 07:58:28 +0000
From: Donald Robson <Donald.Robson@...tec.com>
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Subject: Re: [PATCH drm-next v4 00/14] [RFC] DRM GPUVA Manager & Nouveau
VM_BIND UAPI
On Tue, 2023-06-13 at 16:20 +0200, Danilo Krummrich wrote:
> I'm definitely up improving the existing documentation. Anything in
> particular you think should be described in more detail?
>
> - Danilo
Hi Danilo,
As I said, with inexperience it's possible I missed what I was
looking for in the existing documentation, which is highly detailed
in regard to how it deals with operations, but usage was where I fell
down.
If I understand there are three ways to use this, which are:
1) Using drm_gpuva_insert() and drm_gpuva_remove() directly using
stack va objects.
2) Using drm_gpuva_insert() and drm_gpuva_remove() in a callback
context, after having created ops lists using
drm_gpuva_sm_[un]map_ops_create().
3) Using drm_gpuva_[un]map() in callback context after having
prealloced a node and va objects for map/remap function use,
which must be forwarded in as the 'priv' argument to
drm_gpuva_sm_[un]map().
The first of these is pretty self-explanatory. The second was also
fairly easy to understand, it has an example in your own driver, and
since it takes care of allocs in drm_gpuva_sm_map_ops_create() it
leads to pretty clean code too.
The third case, which I am using in the new PowerVR driver did not
have an example of usage and the approach is quite different to 2)
in that you have to prealloc everything explicitly. I didn't realise
this, so it led to a fair amount of frustration.
I think if you're willing, it would help inexperienced implementers a
lot if there were some brief 'how to' snippets for each of the three
use cases.
Thanks,
Donald
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