[PATCH v2 1/4] drm/panel: Add new helpers for refcounted panel allocatons

[Anusha Srivatsa]

On Thu, Mar 27, 2025 at 11:58 AM Maxime Ripard <mripard at kernel.org> wrote:

> On Thu, Mar 27, 2025 at 10:55:39AM -0400, Anusha Srivatsa wrote:
> > Introduce reference counted allocations for panels to avoid
> > use-after-free. The patch adds the macro devm_drm_bridge_alloc()
> > to allocate a new refcounted panel. Followed the documentation for
> > drmm_encoder_alloc() and devm_drm_dev_alloc and other similar
> > implementations for this purpose.
> >
> > v2: Better documentation for connector_type field - follow drm_panel_init
> > documentation. (Luca)
> > - Clarify the refcount initialisation in comments.(Maxime)
> > - Correct the documentation of the return type (Maxime)
> >
> > Signed-off-by: Anusha Srivatsa <asrivats at redhat.com>
> > ---
> >  drivers/gpu/drm/drm_panel.c | 25 +++++++++++++++++++++++++
> >  include/drm/drm_panel.h     | 23 +++++++++++++++++++++++
> >  2 files changed, 48 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/drm_panel.c b/drivers/gpu/drm/drm_panel.c
> > index
> c627e42a7ce70459f50eb5095fffc806ca45dabf..bdeab5710ee324dc1742fbc77582250960556308
> 100644
> > --- a/drivers/gpu/drm/drm_panel.c
> > +++ b/drivers/gpu/drm/drm_panel.c
> > @@ -355,6 +355,31 @@ struct drm_panel *of_drm_find_panel(const struct
> device_node *np)
> >  }
> >  EXPORT_SYMBOL(of_drm_find_panel);
> >
> > +void *__devm_drm_panel_alloc(struct device *dev, size_t size, size_t
> offset,
> > +                          const struct drm_panel_funcs *funcs,
> > +                          int connector_type)
> > +{
> > +     void *container;
> > +     struct drm_panel *panel;
> > +
> > +     if (!funcs) {
> > +             dev_warn(dev, "Missing funcs pointer\n");
> > +             return ERR_PTR(-EINVAL);
> > +     }
> > +
> > +     container = devm_kzalloc(dev, size, GFP_KERNEL);
> > +     if (!container)
> > +             return ERR_PTR(-ENOMEM);
> > +
> > +     panel = container + offset;
> > +     panel->funcs = funcs;
> > +
> > +     drm_panel_init(panel, dev, funcs, connector_type);
> > +
> > +     return container;
> > +}
> > +EXPORT_SYMBOL(__devm_drm_panel_alloc);
> > +
> >  /**
> >   * of_drm_get_panel_orientation - look up the orientation of the panel
> through
> >   * the "rotation" binding from a device tree node
> > diff --git a/include/drm/drm_panel.h b/include/drm/drm_panel.h
> > index
> a9c042c8dea1a82ef979c7a68204e0b55483fc28..53251c6b11d78149ede3dad41ffa6a88f3c3c58b
> 100644
> > --- a/include/drm/drm_panel.h
> > +++ b/include/drm/drm_panel.h
> > @@ -28,6 +28,7 @@
> >  #include <linux/errno.h>
> >  #include <linux/list.h>
> >  #include <linux/mutex.h>
> > +#include <linux/kref.h>
> >
> >  struct backlight_device;
> >  struct dentry;
> > @@ -268,6 +269,28 @@ struct drm_panel {
> >       bool enabled;
> >  };
> >
> > +void *__devm_drm_panel_alloc(struct device *dev, size_t size, size_t
> offset,
> > +                          const struct drm_panel_funcs *funcs,
> > +                          int connector_type);
> > +
> > +/**
> > + * devm_drm_panel_alloc - Allocate and initialize an refcounted panel
> > + * @dev: struct device of the panel device
> > + * @type: the type of the struct which contains struct &drm_panel
> > + * @member: the name of the &drm_panel within @type
> > + * @funcs: callbacks for this panel
> > + * @connector_type: the connector type (DRM_MODE_CONNECTOR_*)
> corresponding to
> > + * the panel interface
> > + * Returns:
> > + * Pointer to container structure embedding the panel, ERR_PTR on
> failure.
> > + * The reference count is initialised to 1 and is automatically  given
> back
> > + * by devm action.
>
> Sorry, I noticed after the facts, but this can't be in the Returns
> section, it needs to be in the main one.
>
> Maxime, Not really following you. Are you suggesting this explanation
needs to be in the helper documentation
instead of in returns?

Anusha

> Maxime
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.freedesktop.org/archives/dri-devel/attachments/20250327/4c6d2f23/attachment.htm>