Re: [PATCH v2 02/22] drm: Add valid clones check

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On 12/16/2024 6:27 AM, Simona Vetter wrote:
On Sun, Dec 15, 2024 at 06:19:08PM -0800, Abhinav Kumar wrote:
Hi Maxime

Gentle reminder on this one.

We are looking for some advice on how to go about KUnit for this static
function.

Please help with our question below.

Thanks

Abhinav

On 12/6/2024 4:48 PM, Jessica Zhang wrote:


On 9/25/2024 12:23 AM, Maxime Ripard wrote:
On Tue, Sep 24, 2024 at 03:59:18PM GMT, Jessica Zhang wrote:
Check that all encoders attached to a given CRTC are valid
possible_clones of each other.

Signed-off-by: Jessica Zhang <quic_jesszhan@xxxxxxxxxxx>
---
   drivers/gpu/drm/drm_atomic_helper.c | 23 +++++++++++++++++++++++
   1 file changed, 23 insertions(+)

diff --git a/drivers/gpu/drm/drm_atomic_helper.c
b/drivers/gpu/drm/drm_atomic_helper.c
index 43cdf39019a4..cc4001804fdc 100644
--- a/drivers/gpu/drm/drm_atomic_helper.c
+++ b/drivers/gpu/drm/drm_atomic_helper.c
@@ -574,6 +574,25 @@ mode_valid(struct drm_atomic_state *state)
       return 0;
   }
+static int drm_atomic_check_valid_clones(struct
drm_atomic_state *state,
+                     struct drm_crtc *crtc)
+{
+    struct drm_encoder *drm_enc;
+    struct drm_crtc_state *crtc_state =
drm_atomic_get_new_crtc_state(state,
+                                      crtc);
+
+    drm_for_each_encoder_mask(drm_enc, crtc->dev,
crtc_state->encoder_mask) {
+        if ((crtc_state->encoder_mask & drm_enc->possible_clones) !=
+            crtc_state->encoder_mask) {
+            DRM_DEBUG("crtc%d failed valid clone check for mask
0x%x\n",
+                  crtc->base.id, crtc_state->encoder_mask);
+            return -EINVAL;
+        }
+    }
+
+    return 0;
+}
+
   /**
    * drm_atomic_helper_check_modeset - validate state object for
modeset changes
    * @dev: DRM device
@@ -745,6 +764,10 @@ drm_atomic_helper_check_modeset(struct
drm_device *dev,
           ret = drm_atomic_add_affected_planes(state, crtc);
           if (ret != 0)
               return ret;
+
+        ret = drm_atomic_check_valid_clones(state, crtc);
+        if (ret != 0)
+            return ret;
       }

Pretty much the same comment, we should have kunit tests for this.

Hey Maxime,

I'm working on the kunit test for this and had a question on the design
for the unit test:

Since this is a static helper that returns a pretty common error code,
how would you recommend going about making sure that
`drm_atomic_check_valid_clones()` specifically is returning the error
(and not a different part of check_modeset) when testing the
check_valid_clones() failure path?

So the usual way to test very specific things of a big function is to
first setup a driver and atomic request which does pass all checks. And
then do a minimal change which does not pass anymore.

So what you could do here is have 3 connectors 1 crtc, but only the first
two connectors can be cloned. Then do an atomic request with those two
connectors and the crtc. Then the 2nd request is with one of the
connectors replaced with the 3rd one (so it's still a clone config, but
not an invalid one), then have a failure.

Note: I didn't check all the details, I might be getting something wrong
here, but the idea should work.

Hey Sima,

Ack, FWIW this describes something very similar to my planned test cases (my current kunit tests 3 cases -- valid clone, invalid clone, and no clones). Will post the changes later today if there's no major objections to this.

Thanks,

Jessica Zhang


Cheers, Sima


Thanks,

Jessica Zhang


Maxime


--
Simona Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch





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