On Wed, Apr 18, 2018 at 01:39:35PM +0300, Oleksandr Andrushchenko wrote:There is a use-case I have: a display unit on my target has a DMA
On 04/18/2018 01:18 PM, Paul Durrant wrote:My opinion is that there seems to be a more generic way to implement
Ok, so just to summarize, xen-zcopy/hyper-dmabuf as they are now,-----Original Message-----
From: Xen-devel [mailto:xen-devel-bounces@xxxxxxxxxxxxxxxxxxxx] On Behalf
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Dongwon Kim <dongwon.kim@xxxxxxxxx>; airlied@xxxxxxxx;
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Subject: Re: [Xen-devel] [PATCH 0/1] drm/xen-zcopy: Add Xen zero-copy
helper DRM driver
On Wed, Apr 18, 2018 at 11:01:12AM +0300, Oleksandr Andrushchenko
wrote:
On 04/18/2018 10:35 AM, Roger Pau Monnà wrote:After speaking with Oleksandr on IRC, I think the main usage of the
gntdev extension is to:
1. Create a dma-buf from a set of grant references.
2. Share dma-buf and get a list of grant references.
I think this set of operations could be broken into:
1.1 Map grant references into user-space using the gntdev.
1.2 Create a dma-buf out of a set of user-space virtual addresses.
2.1 Map a dma-buf into user-space.
2.2 Get grefs out of the user-space addresses where the dma-buf is
mapped.
So it seems like what's actually missing is a way to:
- Create a dma-buf from a list of user-space virtual addresses.
- Allow to map a dma-buf into user-space, so it can then be used with
the gntdev.
I think this is generic enough that it could be implemented by a
device not tied to Xen. AFAICT the hyper_dma guys also wanted
something similar to this.
are no go from your POV?
this, and thus I would prefer that one.
Instead, we have to make all that fancy stuffThat would be my preference if feasible, simply because it can be
with VAs <-> device-X and have that device-X driver live out of drivers/xen
as it is not a Xen specific driver?
reused by other use-cases that need to create dma-bufs in user-space.
In any case I just knew about dma-bufs this morning, there might be
things that I'm missing.
Roger.