Re: [PATCH] drm: dp_tunnel: use kzalloc_flex

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Tue, Mar 10, 2026 at 03:09:31PM -0700, Rosen Penev wrote:
> On Tue, Mar 10, 2026 at 1:12 AM Ville Syrjälä
> <ville.syrjala@linux.intel.com> wrote:
> >
> > On Sun, Mar 08, 2026 at 02:12:20PM -0700, Rosen Penev wrote:
> > > Simplifies allocation by using a flexible array member to remove a
> > > second kzalloc.
> > >
> > > Added __counted_by for extra runtime analysis.
> > >
> > > Simplify assignment loop. It always returns true. That is,
> > > max_group_count is always equal to group_count.
> > >
> > > Signed-off-by: Rosen Penev <rosenp@gmail.com>
> > > ---
> > >  drivers/gpu/drm/display/drm_dp_tunnel.c | 26 ++++++-------------------
> > >  1 file changed, 6 insertions(+), 20 deletions(-)
> > >
> > > diff --git a/drivers/gpu/drm/display/drm_dp_tunnel.c b/drivers/gpu/drm/display/drm_dp_tunnel.c
> > > index f442430d8de7..aad1605b956e 100644
> > > --- a/drivers/gpu/drm/display/drm_dp_tunnel.c
> > > +++ b/drivers/gpu/drm/display/drm_dp_tunnel.c
> > > @@ -188,13 +188,13 @@ struct drm_dp_tunnel_group {
> > >  struct drm_dp_tunnel_mgr {
> > >       struct drm_device *dev;
> > >
> > > -     int group_count;
> > > -     struct drm_dp_tunnel_group *groups;
> > >       wait_queue_head_t bw_req_queue;
> > >
> > >  #ifdef CONFIG_DRM_DISPLAY_DP_TUNNEL_STATE_DEBUG
> > >       struct ref_tracker_dir ref_tracker;
> > >  #endif
> > > +     int group_count;
> > > +     struct drm_dp_tunnel_group groups[] __counted_by(group_count);
> > >  };
> > >
> > >  /*
> > > @@ -1893,7 +1893,6 @@ static void destroy_mgr(struct drm_dp_tunnel_mgr *mgr)
> > >       ref_tracker_dir_exit(&mgr->ref_tracker);
> > >  #endif
> > >
> > > -     kfree(mgr->groups);
> > >       kfree(mgr);
> > >  }
> > >
> > > @@ -1913,33 +1912,20 @@ drm_dp_tunnel_mgr_create(struct drm_device *dev, int max_group_count)
> > >       struct drm_dp_tunnel_mgr *mgr;
> > >       int i;
> > >
> > > -     mgr = kzalloc_obj(*mgr);
> > > +     mgr = kzalloc_flex(*mgr, groups, max_group_count);
> > >       if (!mgr)
> > >               return ERR_PTR(-ENOMEM);
> > >
> > > +     mgr->group_count = max_group_count;
> > >       mgr->dev = dev;
> > >       init_waitqueue_head(&mgr->bw_req_queue);
> > >
> > > -     mgr->groups = kzalloc_objs(*mgr->groups, max_group_count);
> > > -     if (!mgr->groups) {
> > > -             kfree(mgr);
> > > -
> > > -             return ERR_PTR(-ENOMEM);
> > > -     }
> > > -
> > >  #ifdef CONFIG_DRM_DISPLAY_DP_TUNNEL_STATE_DEBUG
> > >       ref_tracker_dir_init(&mgr->ref_tracker, 16, "drm_dptun");
> > >  #endif
> > >
> > > -     for (i = 0; i < max_group_count; i++) {
> > > -             if (!init_group(mgr, &mgr->groups[i])) {
> > > -                     destroy_mgr(mgr);
> > > -
> > > -                     return ERR_PTR(-ENOMEM);
> > > -             }
> > > -
> > > -             mgr->group_count++;
> > > -     }
> > > +     for (i = 0; i < max_group_count; i++)
> > > +             init_group(mgr, &mgr->groups[i]);
> >
> > This breaks the error handling.
> >
> > Hmm, actually it looks like it already got broken by commit
> > 8e6da25bd60d ("drm/dp_tunnel: Switch private_obj initialization
> > to atomic_create_state")...
> I can't comment on that.
> 
> This patch does not touch that.

You are removing what remains of the error handling, and that part
would have to be undone to fix the earlier breakage.

Maxime, can you fix that up?

> >
> > >
> > >       return mgr;
> > >  }
> > > --
> > > 2.53.0
> >
> > --
> > Ville Syrjälä
> > Intel

-- 
Ville Syrjälä
Intel