Hi Jacopo,
Thank you for the patch.
On Wednesday, 13 December 2017 20:26:19 EET Jacopo Mondi wrote:
> Currently, subdevice notifiers are tested against all available
> subdevices as soon as they get registered. It often happens anyway
> that the subdevice they are connected to is not yet initialized, as
> it usually gets registered later in drivers' code. This makes debug
> of v4l2_async particularly painful, as identifying a notifier with
> an unitialized subdevice is tricky as they don't have a valid
> 'struct device *' or 'struct fwnode_handle *' to be identified with.
>
> In order to make sure that the notifier's subdevices is initialized
> when the notifier is tesed against available subdevices post-pone the
> actual notifier registration at subdevice registration time.
Aren't you piling yet another hack on top of an already dirty framework ? How
about fixing the root cause of the issue and ensuring that subdevs are
properly initialized when the notifier is registered ?
> It is worth noting that post-poning registration of a subdevice notifier
> does not impact on the completion of the notifiers chain, as even if a
> subdev notifier completes as soon as it gets registered, the complete()
> call chain cannot be upscaled as long as the subdevice the notifiers
> belongs to is not registered.
>
> Also, it is now safe to access a notifier 'struct device *' as we're now
> sure it is properly initialized when the notifier is actually
> registered.
>
> Signed-off-by: Jacopo Mondi <jacopo+rene...@jmondi.org>
> ---
> drivers/media/v4l2-core/v4l2-async.c | 65 +++++++++++++++++++++-----------
> include/media/v4l2-async.h | 2 ++
> 2 files changed, 43 insertions(+), 24 deletions(-)
>
> diff --git a/drivers/media/v4l2-core/v4l2-async.c
> b/drivers/media/v4l2-core/v4l2-async.c index 0a1bf1d..c13a781 100644
> --- a/drivers/media/v4l2-core/v4l2-async.c
> +++ b/drivers/media/v4l2-core/v4l2-async.c
[snip]
> @@ -548,6 +551,20 @@ int v4l2_async_register_subdev(struct v4l2_subdev *sd)
> sd->fwnode = dev_fwnode(sd->dev);
> }
>
> + /*
> + * If the subdevice has an unregisterd notifier, it's now time
> + * to register it.
> + */
> + subdev_notifier = sd->subdev_notifier;
> + if (subdev_notifier && !subdev_notifier->registered) {
> + ret = __v4l2_async_notifier_register(subdev_notifier);
> + if (ret) {
> + sd->fwnode = NULL;
> + subdev_notifier->owner = NULL;
> + return ret;
> + }
> + }
This is the part I like the least in this patch set. The
v4l2_subdev::subdev_notifier field should really disappear, there's no reason
to limit subdevs to a single notifier. Implicit registration of notifiers is a
dirty hack in my opinion.
> mutex_lock(&list_lock);
>
> INIT_LIST_HEAD(&sd->async_list);
[snip]
--
Regards,
Laurent Pinchart
