[PATCH v2 3/4] drm/dp_mst: Check payload count in drm_dp_mst_atomic_check()

[Lyude Paul]

On Mon, 2018-10-29 at 15:25 +0100, Daniel Vetter wrote:
> On Fri, Oct 26, 2018 at 04:35:48PM -0400, Lyude Paul wrote:
> > It occurred to me that we never actually check this! So let's start
> > doing that.
> > 
> > Signed-off-by: Lyude Paul <lyude at redhat.com>
> > Cc: Daniel Vetter <daniel.vetter at ffwll.ch>
> 
> Reviewed-by: Daniel Vetter <daniel.vetter at ffwll.ch>
> 
> One thought on testing all this: I think long term some unti tests, where
> we have a fake driver doing fake mst branch/ports and a bunch of
> allocations and then checking that it all works and validates would be
> nice. Longer term project ofc, and maybe after Kunit has been merged ...
mhm-you see why I was considering how we could use vkms with this :), but yeah
getting unit tests is one of the reasons I'm hoping to move some more MST
logic out into the DRM helpers
> -Daniel
> 
> > ---
> >  drivers/gpu/drm/drm_dp_mst_topology.c | 8 +++++++-
> >  1 file changed, 7 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c
> > b/drivers/gpu/drm/drm_dp_mst_topology.c
> > index dcfab7536914..8bb03700e199 100644
> > --- a/drivers/gpu/drm/drm_dp_mst_topology.c
> > +++ b/drivers/gpu/drm/drm_dp_mst_topology.c
> > @@ -3238,7 +3238,7 @@ int drm_dp_mst_atomic_check(struct
> > drm_dp_mst_topology_state *state)
> >  {
> >  	struct drm_dp_mst_topology_mgr *mgr = state->mgr;
> >  	struct drm_dp_vcpi_allocation *pos;
> > -	int avail_slots = 63;
> > +	int avail_slots = 63, payload_count = 0;
> >  
> >  	list_for_each_entry(pos, &state->vcpis, next) {
> >  		DRM_DEBUG_ATOMIC("[MST PORT:%p] requires %d vcpi slots\n",
> > @@ -3251,6 +3251,12 @@ int drm_dp_mst_atomic_check(struct
> > drm_dp_mst_topology_state *state)
> >  					 avail_slots + pos->vcpi);
> >  			return -ENOSPC;
> >  		}
> > +
> > +		if (++payload_count > mgr->max_payloads) {
> > +			DRM_DEBUG_ATOMIC("[MST MGR:%p] state %p has too many
> > payloads (max=%d)\n",
> > +					 mgr, state, mgr->max_payloads);
> > +			return -EINVAL;
> > +		}
> >  	}
> >  	DRM_DEBUG_ATOMIC("[MST MGR:%p] state %p vcpi avail=%d used=%d\n",
> >  			 mgr, state, avail_slots, 63 - avail_slots);
> > -- 
> > 2.17.2
> > 
> 
> 
-- 
Cheers,
	Lyude Paul