On Tue, Dec 16, 2014 at 06:05:29PM -0500, Rob Clark wrote:
> We can already have object properties, which technically can be fb's.
> Switch the property validation logic over to a get/put style interface
> so it can take a ref to refcnt'd objects, and then drop that ref after
> the driver has a chance to take it's own ref.
>
> Signed-off-by: Rob Clark <robdclark at gmail.com>
Yeah I think of all the options we've looked at this is the best wrt to
interface safety.
Reviewed-by: Daniel Vetter <daniel.vetter at ffwll.ch>
> ---
> drivers/gpu/drm/drm_crtc.c | 58
> ++++++++++++++++++++++++++++++++++------------
> 1 file changed, 43 insertions(+), 15 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_crtc.c b/drivers/gpu/drm/drm_crtc.c
> index 5213da4..5ee4b88 100644
> --- a/drivers/gpu/drm/drm_crtc.c
> +++ b/drivers/gpu/drm/drm_crtc.c
> @@ -4193,12 +4193,22 @@ int drm_mode_connector_update_edid_property(struct
> drm_connector *connector,
> }
> EXPORT_SYMBOL(drm_mode_connector_update_edid_property);
>
> -static bool drm_property_change_is_valid(struct drm_property *property,
> - uint64_t value)
> +/* Some properties could refer to dynamic refcnt'd objects, or things that
> + * need special locking to handle lifetime issues (ie. to ensure the prop
> + * value doesn't become invalid part way through the property update due to
> + * race). The value returned by reference via 'obj' should be passed back
> + * to drm_property_change_valid_put() after the property is set (and the
> + * object to which the property is attached has a chance to take it's own
> + * reference).
> + */
> +static bool drm_property_change_valid_get(struct drm_property *property,
> + uint64_t value, struct drm_mode_object
> **ref)
> {
> if (property->flags & DRM_MODE_PROP_IMMUTABLE)
> return false;
>
> + *ref = NULL;
> +
> if (drm_property_type_is(property, DRM_MODE_PROP_RANGE)) {
> if (value < property->values[0] || value > property->values[1])
> return false;
> @@ -4219,19 +4229,23 @@ static bool drm_property_change_is_valid(struct
> drm_property *property,
> /* Only the driver knows */
> return true;
> } else if (drm_property_type_is(property, DRM_MODE_PROP_OBJECT)) {
> - struct drm_mode_object *obj;
> /* a zero value for an object property translates to null: */
> if (value == 0)
> return true;
> - /*
> - * NOTE: use _object_find() directly to bypass restriction on
> - * looking up refcnt'd objects (ie. fb's). For a refcnt'd
> - * object this could race against object finalization, so it
> - * simply tells us that the object *was* valid. Which is good
> - * enough.
> - */
> - obj = _object_find(property->dev, value, property->values[0]);
> - return obj != NULL;
> +
> + /* handle refcnt'd objects specially: */
> + if (property->values[0] == DRM_MODE_OBJECT_FB) {
> + struct drm_framebuffer *fb;
> + fb = drm_framebuffer_lookup(property->dev, value);
> + if (fb) {
> + *ref = &fb->base;
> + return true;
> + } else {
> + return false;
> + }
> + } else {
> + return _object_find(property->dev, value,
> property->values[0]) != NULL;
> + }
> } else {
> int i;
> for (i = 0; i < property->num_values; i++)
> @@ -4241,6 +4255,18 @@ static bool drm_property_change_is_valid(struct
> drm_property *property,
> }
> }
>
> +static void drm_property_change_valid_put(struct drm_property *property,
> + struct drm_mode_object *ref)
> +{
> + if (!ref)
> + return;
> +
> + if (drm_property_type_is(property, DRM_MODE_PROP_OBJECT)) {
> + if (property->values[0] == DRM_MODE_OBJECT_FB)
> + drm_framebuffer_unreference(obj_to_fb(ref));
> + }
> +}
> +
> /**
> * drm_mode_connector_property_set_ioctl - set the current value of a
> connector property
> * @dev: DRM device
> @@ -4429,8 +4455,8 @@ int drm_mode_obj_set_property_ioctl(struct drm_device
> *dev, void *data,
> struct drm_mode_object *arg_obj;
> struct drm_mode_object *prop_obj;
> struct drm_property *property;
> - int ret = -EINVAL;
> - int i;
> + int i, ret = -EINVAL;
> + struct drm_mode_object *ref;
>
> if (!drm_core_check_feature(dev, DRIVER_MODESET))
> return -EINVAL;
> @@ -4460,7 +4486,7 @@ int drm_mode_obj_set_property_ioctl(struct drm_device
> *dev, void *data,
> }
> property = obj_to_property(prop_obj);
>
> - if (!drm_property_change_is_valid(property, arg->value))
> + if (!drm_property_change_valid_get(property, arg->value, &ref))
> goto out;
>
> switch (arg_obj->type) {
> @@ -4477,6 +4503,8 @@ int drm_mode_obj_set_property_ioctl(struct drm_device
> *dev, void *data,
> break;
> }
>
> + drm_property_change_valid_put(property, ref);
> +
> out:
> drm_modeset_unlock_all(dev);
> return ret;
> --
> 2.1.0
>
--
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch
