On 04/05/17 07:52, Emil Velikov wrote:
On 4 May 2017 at 14:46, Daniel Vetter <dan...@ffwll.ch> wrote:
On Thu, Apr 27, 2017 at 10:58:42AM -0700, Lionel Landwerlin wrote:
On 27/04/17 08:20, Eric Anholt wrote:
Emil Velikov <emil.l.veli...@gmail.com> writes:
On 25 April 2017 at 23:56, Lionel Landwerlin
<lionel.g.landwer...@intel.com> wrote:
Hi,
While working with changes that span from kernel to user space, I've
been wondering whether we need to depend on libdrm at all for the anv
& i965 drivers. Indeed with Ken's recent changes, we only depend on
libdrm for its kernel header files which we could just embed
ourselves.
I've only included the minimal set of header files we need from the
kernel for anv & i965. Maybe other drivers would be interested and
maybe we should put all the kernel drm uapi headers into include?
AFAICT the goal behind the libdrm_intel fold was to allow rapid and
seamless rework of the interface.
With a potential goal to make it a shared one, as it gets stabilised.
Currently ANV uses more than just the UAPI headers. But if we ignore
that, coping them is a bad idea.
What else is anv using from libdrm? (maybe I missed something)
Lionel, I stand corrected, we have instances in anv, wsi/x11, loader
and dri/i965 (the dri/common ones are just comments).
In total they seem to be over three dozen instances. Experiment with
the following:
for i in `nm -CD --defined-only /lib/libdrm.so | cut -c 20-| grep -v
"^_" `; do git grep -w --name-only $i -- src ; done
Thanks for the code snippet.
For anv :
drmGetDevices2
For i965 :
drmCommandNone
drmCommandWriteRead
drmIoctl
drmPrimeFDToHandle
drmPrimeHandleToFD
You're right, I'll update the patch to just drop libdrm_intel.
Why - adds a, yet another, copy and making synchronisation more
annoying. First example - you blindly copied the files rather than
using `make headers_install' first ;-)
Not to mention that it makes the chicken and egg problem* even more
confusing and error prone.
It doesn't feel like that to me. Actually instead of modifying 3 different
repos, you end up modifying just 2.
Sounds less error prone.
Lionel, are you saying that we can ignore IGT? Or you're suggesting
that IGT should depend on Mesa copy of the headers?
If you look closely at IGT, you'll notice quite a few tests actually
define their own version of the structures/ioctl of the various driver
interfaces.
So it's more or less already happening.
git grep DRM_IO ./tests/ | grep define
git grep local_drm
Seriously, your argument of "let's import because we can" is iffy. Why
stop with the DRM UAPI - let's import headers from glibc ;-)
I think you have to look at what we're doing here. i965 & anv are
graphics drivers tightly coupled with the kernel driver.
libdrm_intel isn't, it's mostly generic enough code that is shared
across some of our drivers.
And since we drop that dependency, why bother with it at all?
We don't really have the same relationship to other components (like glibc).
If pulling new libdrm is that much of a nuisance to your workflow -
just copy the blob we have for the Travis instance.
It automatically tracks the libdrm version, builds and installs it as needed.
It's not about pulling, it's about maintaining.
Emil
* Which patches land first - kernel or userspace
I don't see how it does that at all. It simplifies the process: Now you
send out your proposed new userspace to one repo, instead of two.
And, after the first commit, it'll be obvious when you screw up using
make headers_install because there will be surprising diff.
Right now we have to update libdrm, then update the mesa to depend on the
right libdrm to actually get the header files we want.
If you depend on libdrm from more than just uapi headers, it might now be
too much of a burden. But it seems we're clearly moving away from that in
anv/i965.
As a developer it feels a lot easier to have just the update mesa with both
the new kernel API you depend on & the changes to the user space driver
using that API.
As long as the headers are never installed into the system I'm in
principle ok with pulling all the i915.ko specific stuff into mesa. Seems
like a reasonable thing to do.
Daniel, Lionel's earlier suggestion (see the "modifying just 2" part
above) implies that either a) Mesa should install these or b) we can
ignore other components such as IGT.
Neither of which sounds cool IMHO.
Feel pretty cool to me.
I don't think I can put it better than Eric did :
On 04/05/17 09:38, Eric Anholt wrote:
And it works great, because kernel headers are backwards compatible.
When you need a feature, you just merge the header update necessary and
no other developers get disrupted.
Have you done kernel API feature development? I feel like this is the
kind of thing you need to do yourself several times, with several
revisions over the course of months, before understanding the
limitations of our current process.
Of course still the same rules apply for merging new uapi: All parts must
be reviewed, then we merge the kernel, and only afterwards userspace. The
headers process in libdrm (see libdrm/include/drm/README) is imo the best
model for that.
Right that's another part of my argument. We are just about keeping
developers to follow those.
Copying the headers here will make it even easier for people to ignore
the procedure.
Not saying that people intentionally ignore it - sometimes we're
tired, having a bad day, etc.
At the same time tracking the same thing twice is simply a waste of
time - let's not do it.
Thanks
Emil
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