Re: [Intel-gfx] [igt-dev] [PATCH i-g-t v5 1/6] lib/igt_kms: Add writeback support

[Rodrigo Siqueira <rodrigosiqueiramelo@gmail.com>]

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Hi Liviu,

I’m using your patchset to guide my implementation of writeback in the
VKMS, so, first of all, thanks :)

During my work, I noticed that you’re setting the drmSetClientCap()
before drmModeGetResources() which make the writeback capability
‘invisible’ for drmModeGetResources(). I made the following change, and
I could pass the igt_display_require():

diff --git a/lib/igt_kms.c b/lib/igt_kms.c
index f4ff3a96..bb2d8e06 100644
--- a/lib/igt_kms.c
+++ b/lib/igt_kms.c
@@ -1912,6 +1912,12 @@ void igt_display_require(igt_display_t *display, int drm_fd)
 
        display->drm_fd = drm_fd;
 
+       drmSetClientCap(drm_fd, DRM_CLIENT_CAP_UNIVERSAL_PLANES, 1);
+       if (drmSetClientCap(drm_fd, DRM_CLIENT_CAP_ATOMIC, 1) == 0)
+               display->is_atomic = 1;
+
+       drmSetClientCap(drm_fd, DRM_CLIENT_CAP_WRITEBACK_CONNECTORS, 1);
+
        resources = drmModeGetResources(display->drm_fd);
        if (!resources)
                goto out;
@@ -1924,12 +1930,6 @@ void igt_display_require(igt_display_t *display, int drm_fd)
        display->pipes = calloc(sizeof(igt_pipe_t), display->n_pipes);
        igt_assert_f(display->pipes, "Failed to allocate memory for %d pipes\n", display->n_pipes);
 
-       drmSetClientCap(drm_fd, DRM_CLIENT_CAP_UNIVERSAL_PLANES, 1);
-       if (drmSetClientCap(drm_fd, DRM_CLIENT_CAP_ATOMIC, 1) == 0)
-               display->is_atomic = 1;
-
-       drmSetClientCap(drm_fd, DRM_CLIENT_CAP_WRITEBACK_CONNECTORS, 1);
-
        plane_resources = drmModeGetPlaneResources(display->drm_fd);
        igt_assert(plane_resources);

I'm not 100% confident about this issue, because of this I will send an
RFC and see if I can get more details about this issue.

Additionally, if you need any help with this patchset I will be glad to
help since I’m using it \o/

Best Regards
Rodrigo Siqueira

On 02/04, Brian Starkey wrote:
> Hi Liviu,
> 
> On Tue, Jan 15, 2019 at 05:47:42PM +0000, Liviu Dudau wrote:
> > From: Brian Starkey <brian.starkey@arm.com>
> 
> [snip]
> 
> >  
> > +/**
> > + * igt_output_set_writeback_fb:
> > + * @output: Target output
> > + * @fb: Target framebuffer
> > + *
> > + * This function sets the given @fb to be used as the target framebuffer for the
> > + * writeback engine at the next atomic commit. It will also request a writeback
> > + * out fence that will contain the fd number of the out fence created by KMS if
> > + * the given @fb is valid.
> > + */
> > +void igt_output_set_writeback_fb(igt_output_t *output, struct igt_fb *fb)
> > +{
> > +	igt_display_t *display = output->display;
> > +
> > +	LOG(display, "%s: output_set_writeback_fb(%d)\n", output->name, fb ? fb->fb_id : 0);
> > +
> > +	igt_output_set_prop_value(output, IGT_CONNECTOR_WRITEBACK_FB_ID, fb ? fb->fb_id : 0);
> > +	/* only request a writeback out fence if the framebuffer is valid */
> > +	if (fb)
> > +		igt_output_set_prop_value(output, IGT_CONNECTOR_WRITEBACK_OUT_FENCE_PTR,
> > +					  (ptrdiff_t)&output->writeback_out_fence_fd);
> 
> I'm still not sure (ptrdiff_t) is the right type here, (uintptr_t)
> seems better.
> 
> Thanks,
> -Brian
> _______________________________________________
> igt-dev mailing list
> igt-dev@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/igt-dev

-- 
Rodrigo Siqueira
https://siqueira.tech
Graduate Student
Department of Computer Science
University of São Paulo

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