Re: [PATCH] drm/vkms: Add setup and testing information

[Melissa Wen]

Hi Sumera,

Thanks for the doc improvements.
Please see some complimentary comments below.

On 12/03, Daniel Vetter wrote:
> On Thu, Dec 3, 2020 at 8:13 PM Sumera Priyadarsini
> <sylphrenadin@xxxxxxxxx> wrote:
> >
> > Update the vkms documentation to contain steps to:
> >
> >  - setup the vkms driver
> >  - run tests using igt
> >
> > Signed-off-by: Sumera Priyadarsini <sylphrenadin@xxxxxxxxx>
> > ---
> >  Documentation/gpu/vkms.rst | 47 ++++++++++++++++++++++++++++++++++++++
> >  1 file changed, 47 insertions(+)
> >
> > diff --git a/Documentation/gpu/vkms.rst b/Documentation/gpu/vkms.rst
> > index 13bab1d93bb3..d6782174d23f 100644
> > --- a/Documentation/gpu/vkms.rst
> > +++ b/Documentation/gpu/vkms.rst
> > @@ -7,6 +7,53 @@
> >  .. kernel-doc:: drivers/gpu/drm/vkms/vkms_drv.c
> >     :doc: vkms (Virtual Kernel Modesetting)
> >
> > +SETUP
> 
> Absolute bikeshed, but we generally stick to titlecase for titles, so
> just "Setup" and "Testing with IGT".
> > +=====
> > +
> > +The VKMS driver can be setup with the following steps:
> > +
> > +To check if VKMS is loaded, run::
> > +
> > +  lsmod | grep vkms
> > +
> > +This should list the VKMS driver. If no output is obtained, then
> > +you need to enable and/or load the VKMS driver.
> > +Ensure that the VKMS driver has been set as a loadable module in your
> > +kernel config file. The following line should be present in the .config
> > +file in your kernel root::
> > +
> > +  CONFIG_DRM_VKMS=m
> > +

Considering the target audience, I would make it clearer to explore the
configuration options using "make *config". As in
https://kernelnewbies.org/FirstKernelPatch#Recompiling_the_driver

> > +Compile and build the kernel for the changes to get reflected.
> > +If your existing config already has VKMS available as a loadable module,
> > +then there is no need to build the kernel again.
> > +Now, to load the driver, use::
> > +
> > +  sudo modprobe vkms
> > +
> > +On running the lsmod command now, the VKMS driver will appear listed.
> > +You can also observe the driver being loaded in the dmesg logs.
> > +
> > +To disable the driver, use ::
s/disable/unload/
> > +
> > +  sudo modprobe -r vkms
> > +
> > +TESTING WITH IGT
> > +================
> > +
> > +The IGT GPU Tools is a test suite used specifically for debugging and
> > +development of the DRM drivers.
> > +The IGT Tools can be installed from
> > +`here <https://gitlab.freedesktop.org/drm/igt-gpu-tools>`_ .
> > +Once you have installed IGT, you can run tests using::
> > +
> > +  ./scripts/run-tests.sh -t <name of test>
> > +
> > +For example, to test the functionality of the igt_draw library,
> > +we can run the kms_draw_crc test::
> > +
> > +  ./scripts/run-tests.sh -t kms_draw_crc
> 
> If we run igt tests directly, there's an option to select the right
> device. This is important if you have more than one gpu driver
> (usually the case if you run this directly, but even on virtual
> machines there should usually be a drm driver around).  E.g. when I
> run a test directly:
> 
> # tests/kms_flip --device drm:/dev/dri/card0
> 
> I'm not sure whether there's an option that's always going to select
> the vkms device. I'm also not sure you can pass these options to
> run-tests.sh, I kinda don't use that one myself ...

I also run a test directly. Some cases have many subtests, therefore I
can pass --run-subtest to specify one.

And, to select vkms, I use IGT_FORCE_DRIVER. For example:

# IGT_FORCE_DRIVER=vkms tests/kms_flip --run-subtest basic-plain-flip

> 
> Aside from that looks all good to me.
+1

Melissa
> -Daniel
> 
> > +
> >  TODO
> >  ====
> >
> > --
> > 2.25.1
> >
> 
> 
> -- 
> Daniel Vetter
> Software Engineer, Intel Corporation
> http://blog.ffwll.ch