On 03/28/2016 12:28 PM, Mauro Carvalho Chehab wrote: > Em Fri, 25 Mar 2016 22:38:43 -0600 > Shuah Khan <shuahkh@xxxxxxxxxxxxxxx> escreveu: > >> Add Media Device Allocator API documentation. > > Please merge this with the previous patch. Yes. I will merge them. -- Shuah > >> >> Signed-off-by: Shuah Khan <shuahkh@xxxxxxxxxxxxxxx> >> --- >> 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 > > _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
