On 04/19/2012 01:40 PM, Thierry Reding wrote:
* PGP Signed by an unknown key
* Dave Airlie wrote:
On Thu, Apr 19, 2012 at 6:35 PM, Thierry Reding
<thierry.reding@xxxxxxxxxxxxxxxxx> wrote:
Before posting the next round of patches I wanted to clarify whether we need
to take the Tegra driver through staging. Lucas brought this up referring to
previous experience with Nouveau where Linus used to complain that userspace
ABI was broken for non-staging drivers. I don't know how relevant that is
for Tegra. We could also keep it in drivers/gpu/drm and only add userspace
interfaces that we are sure are not going to change. Currently there isn't
isn't anything that could be easily broken as only some of the standard DRM
interfaces are supported anyway.
Alternatively we could keep the driver in a separate tree until it becomes
mature enough.
Any thoughts?
It's probably okay to avoid staging if it doesn't add any userspace ioctls.
A KMS driver that just supports the dumb ioctls so -modesetting works,
would be the first thing to aim for I suppose, like how the exynos
guys did it.
Adding userspace interfaces is where you'll get into ABI guarantees
etc, and these are normally required only for the accel engines.
I think this is what Lucas was concerned about. The plan is to look at how
much can be used from the Nouveau code and make it work on the Tegra. So
would it be possible to get a basic dumb KMS driver into mainline
(non-staging) and phase in acceleration later on, with ABI guarantees? I
guess development can go on in separate trees until the ABI is stable and can
subsequently be ported to the mainline driver.
Is that an acceptable approach?
Thierry
That certainly seems like the most reasonable approach to me. Get KMS
only in first. It's a useful driver as-is, and has the lowest barrier to
entry into upstream.
Then later we can phase in enhancements. We certainly have plenty of
places internally and externally to hash out acceleration interfaces,
and come to some consensus at at later date (either on linux-tegra or
direct email).
We have a lot of concerns here. What is best for X11, what is best for
Android, how do we keep healthy open source implementations, and how
does NVIDIA move forward with supporting new Tegra on an open source
implementation. (My vote is NVIDIA starts using this DRM in-house and
builds new extensions on top of it, sharing patches on LKML when the
hardware is released)
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