Re: [PATCH] drm: dp_tunnel: use kzalloc_flex

[Rosen Penev]

On Tue, Mar 10, 2026 at 1:12 AM Ville Syrjälä
<ville.syrjala@xxxxxxxxxxxxxxx> 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@xxxxxxxxx>
> > ---
> >  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.
>
> >
> >       return mgr;
> >  }
> > --
> > 2.53.0
>
> --
> Ville Syrjälä
> Intel