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    SubjectRe: [RFC PATCH 2/4] media: Add Media Device Allocator API documentation
    Em Fri, 25 Mar 2016 22:38:43 -0600
    Shuah Khan <shuahkh@osg.samsung.com> escreveu:

    > Add Media Device Allocator API documentation.

    Please merge this with the previous patch.

    >
    > Signed-off-by: Shuah Khan <shuahkh@osg.samsung.com>
    > ---
    > include/media/media-dev-allocator.h | 32 ++++++++++++++++++++++++++++++++
    > 1 file changed, 32 insertions(+)
    >
    > diff --git a/include/media/media-dev-allocator.h b/include/media/media-dev-allocator.h
    > index 2932c90..174840c 100644
    > --- a/include/media/media-dev-allocator.h
    > +++ b/include/media/media-dev-allocator.h
    > @@ -20,6 +20,38 @@
    >
    > #ifdef CONFIG_MEDIA_CONTROLLER
    > /**
    > + * DOC: Media Controller Device Allocator API
    > + * There are known problems with media device life time management. When media
    > + * device is released while an media ioctl is in progress, ioctls fail with
    > + * use-after-free errors and kernel hangs in some cases.
    > + *
    > + * Media Device can be in any the following states:
    > + *
    > + * - Allocated
    > + * - Registered (could be tied to more than one driver)
    > + * - Unregistered, not in use (media device file is not open)
    > + * - Unregistered, in use (media device file is not open)
    > + * - Released
    > + *
    > + * When media device belongs to more than one driver, registrations should be
    > + * refcounted to avoid unregistering when one of the drivers does unregister.
    > + * A refcount field in the struct media_device covers this case. Unregister on
    > + * a Media Allocator media device is a kref_put() call. The media device should
    > + * be unregistered only when the last unregister occurs.
    > + *
    > + * When a media device is in use when it is unregistered, it should not be
    > + * released until the application exits when it detects the unregistered
    > + * status. Media device that is in use when it is unregistered is moved to
    > + * to_delete_list. When the last unregister occurs, media device is unregistered
    > + * and becomes an unregistered, still allocated device. Unregister marks the
    > + * device to be deleted.
    > + *
    > + * When media device belongs to more than one driver, as both drivers could be
    > + * unbound/bound, driver should not end up getting stale media device that is
    > + * on its way out. Moving the unregistered media device to to_delete_list helps
    > + * this case as well.
    > + */
    > +/**
    > * media_device_get() - Allocate and return global media device
    > *
    > * @mdev


    --
    Thanks,
    Mauro

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