Messages in this thread | | | Subject | Re: [PATCH v9 4/4] sound/usb: Use Media Controller API to share media resources | From | shuah <> | Date | Fri, 18 Jan 2019 14:54:18 -0700 |
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On 1/18/19 1:36 AM, Hans Verkuil wrote: > On 12/18/18 6:59 PM, shuah@kernel.org wrote: >> From: Shuah Khan <shuah@kernel.org> >> >> Media Device Allocator API to allows multiple drivers share a media device. >> This API solves a very common use-case for media devices where one physical >> device (an USB stick) provides both audio and video. When such media device >> exposes a standard USB Audio class, a proprietary Video class, two or more >> independent drivers will share a single physical USB bridge. In such cases, >> it is necessary to coordinate access to the shared resource. >> >> Using this API, drivers can allocate a media device with the shared struct >> device as the key. Once the media device is allocated by a driver, other >> drivers can get a reference to it. The media device is released when all >> the references are released. >> >> Change the ALSA driver to use the Media Controller API to share media >> resources with DVB, and V4L2 drivers on a AU0828 media device. >> >> The Media Controller specific initialization is done after sound card is >> registered. ALSA creates Media interface and entity function graph nodes >> for Control, Mixer, PCM Playback, and PCM Capture devices. >> >> snd_usb_hw_params() will call Media Controller enable source handler >> interface to request the media resource. If resource request is granted, >> it will release it from snd_usb_hw_free(). If resource is busy, -EBUSY is >> returned. >> >> Media specific cleanup is done in usb_audio_disconnect(). >> >> Signed-off-by: Shuah Khan <shuah@kernel.org> >> --- >> sound/usb/Kconfig | 4 + >> sound/usb/Makefile | 2 + >> sound/usb/card.c | 14 ++ >> sound/usb/card.h | 3 + >> sound/usb/media.c | 321 +++++++++++++++++++++++++++++++++++++++ >> sound/usb/media.h | 74 +++++++++ >> sound/usb/mixer.h | 3 + >> sound/usb/pcm.c | 29 +++- >> sound/usb/quirks-table.h | 1 + >> sound/usb/stream.c | 2 + >> sound/usb/usbaudio.h | 6 + >> 11 files changed, 455 insertions(+), 4 deletions(-) >> create mode 100644 sound/usb/media.c >> create mode 100644 sound/usb/media.h >> > > <snip> > >> +int snd_media_device_create(struct snd_usb_audio *chip, >> + struct usb_interface *iface) >> +{ >> + struct media_device *mdev; >> + struct usb_device *usbdev = interface_to_usbdev(iface); >> + int ret; >> + >> + /* usb-audio driver is probed for each usb interface, and >> + * there are multiple interfaces per device. Avoid calling >> + * media_device_usb_allocate() each time usb_audio_probe() >> + * is called. Do it only once. >> + */ >> + if (chip->media_dev) >> + goto snd_mixer_init; >> + >> + mdev = media_device_usb_allocate(usbdev, KBUILD_MODNAME); >> + if (!mdev) >> + return -ENOMEM; >> + >> + if (!media_devnode_is_registered(mdev->devnode)) { > > It looks like you missed my comment for v8: > > "You should first configure the media device before registering it." > > In other words, first create the media entities, and only then do you > register the media device. Otherwise it will come up without any alsa > entities, which are then added. So an application that immediately > opens the media device upon creation will see a topology that is still > in flux.
Yes. You are right. I saw your comment and thought I got it addressed. I will fix it. I have the logic correct in au0828, but not here.
Thanks, -- Shuah
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