Em Mon, 23 Nov 2015 23:10:04 +0200
Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx> escreveu:
> Hi Mauro,
>
> Thank you for the patch.
>
> On Sunday 06 September 2015 09:03:13 Mauro Carvalho Chehab wrote:
> > V4L2 device (and subdevice) nodes should create an interface, if the
> > Media Controller support is enabled.
> >
> > Please notice that radio devices should not create an entity, as radio
> > input/output is either via wires or via ALSA.
>
> I'd go one step further, video nodes should not create an entity, ever. This
> was one of the design principles behind the MC rework. We'll need to patch
> drivers to create DMA engine entity explicitly, possibly through a helper
> function (maybe a function to create and initialize a DMA engine entity based
> on a struct video_device). This can of course be done on a separate patch, but
> removing the entity field from struct video_device should be part of the
> series.
Not sure what exactly you mean here.
There are two separate things happening with regards to device
nodes that do stream I/O:
1) They may have a DMA engine somewhere at the hardware pipeline.
On some drivers, like USB ones, the DMA engine is actually not
responsible to deliver the data to userspace. This is also
true on ALSA and DVB (right now). Also, eventually, some
drivers may not have a DMA engine (they may eventually use PIO
like some old sound cards);
2) The I/O interface to where the data stream is delivered. This is
actually not a hardware interface, but a software implementation
on Linux. Ok, on V4L2, this is typically associated with a DMA
engine, but the actual interface is a buffer that could be
obtained by one of the delivery methods: read()/write() sysctl,
mmapped buffer and/or DMABUF.
IMHO, (2) would ideally be mapped as a media_interface, as this is
not hardware, but linux software. However, such change won't be
backward compatible. So, as agreed at the MC workshop, we're using
a media entity for such I/O interface, calling its function as
MEDIA_ENT_F_IO (as you may see at the review comments from the
others, Shuah requested to actually split this function into one
I/O function per type of interface, in order to be able to easily
distinguish ALSA I/O from V4L2 I/O).
I agree that (1) should be driver-specific, as only the driver knows
where the DMA engine is at the pipeline.
However, (2) should be created by the media core. So, I can't see
any rationale to remove the entity field from struct video_device.
>
> > Signed-off-by: Mauro Carvalho Chehab <mchehab@xxxxxxxxxxxxxxx>
> >
> > diff --git a/drivers/media/v4l2-core/v4l2-dev.c
> > b/drivers/media/v4l2-core/v4l2-dev.c index 44b330589787..07123dd569c4
> > 100644
> > --- a/drivers/media/v4l2-core/v4l2-dev.c
> > +++ b/drivers/media/v4l2-core/v4l2-dev.c
> > @@ -194,9 +194,12 @@ static void v4l2_device_release(struct device *cd)
> > mutex_unlock(&videodev_lock);
> >
> > #if defined(CONFIG_MEDIA_CONTROLLER)
> > - if (v4l2_dev->mdev &&
> > - vdev->vfl_type != VFL_TYPE_SUBDEV)
> > - media_device_unregister_entity(&vdev->entity);
> > + if (v4l2_dev->mdev) {
> > + /* Remove interfaces and interface links */
> > + media_devnode_remove(vdev->intf_devnode);
> > + if (vdev->entity.type != MEDIA_ENT_T_UNKNOWN)
> > + media_device_unregister_entity(&vdev->entity);
> > + }
> > #endif
> >
> > /* Do not call v4l2_device_put if there is no release callback set.
> > @@ -713,6 +716,92 @@ static void determine_valid_ioctls(struct video_device
> > *vdev) BASE_VIDIOC_PRIVATE);
> > }
> >
> > +
>
> Extra blank line.
>
> > +static int video_register_media_controller(struct video_device *vdev, int
> > type)
> > +{
> > +#if defined(CONFIG_MEDIA_CONTROLLER)
> > + u32 intf_type;
> > + int ret;
> > +
> > + if (!vdev->v4l2_dev->mdev)
> > + return 0;
> > +
> > + vdev->entity.type = MEDIA_ENT_T_UNKNOWN;
> > +
> > + switch (type) {
> > + case VFL_TYPE_GRABBER:
> > + intf_type = MEDIA_INTF_T_V4L_VIDEO;
> > + vdev->entity.type = MEDIA_ENT_T_V4L2_VIDEO;
> > + break;
> > + case VFL_TYPE_VBI:
> > + intf_type = MEDIA_INTF_T_V4L_VBI;
> > + vdev->entity.type = MEDIA_ENT_T_V4L2_VBI;
> > + break;
> > + case VFL_TYPE_SDR:
> > + intf_type = MEDIA_INTF_T_V4L_SWRADIO;
> > + vdev->entity.type = MEDIA_ENT_T_V4L2_SWRADIO;
> > + break;
> > + case VFL_TYPE_RADIO:
> > + intf_type = MEDIA_INTF_T_V4L_RADIO;
> > + /*
> > + * Radio doesn't have an entity at the V4L2 side to represent
> > + * radio input or output. Instead, the audio input/output goes
> > + * via either physical wires or ALSA.
> > + */
> > + break;
> > + case VFL_TYPE_SUBDEV:
> > + intf_type = MEDIA_INTF_T_V4L_SUBDEV;
> > + /* Entity will be created via v4l2_device_register_subdev() */
> > + break;
> > + default:
> > + return 0;
> > + }
> > +
> > + if (vdev->entity.type != MEDIA_ENT_T_UNKNOWN) {
> > + vdev->entity.name = vdev->name;
> > +
> > + /* Needed just for backward compatibility with legacy MC API */
> > + vdev->entity.info.dev.major = VIDEO_MAJOR;
> > + vdev->entity.info.dev.minor = vdev->minor;
> > +
> > + ret = media_device_register_entity(vdev->v4l2_dev->mdev,
> > + &vdev->entity);
> > + if (ret < 0) {
> > + printk(KERN_WARNING
> > + "%s: media_device_register_entity failed\n",
> > + __func__);
> > + return ret;
> > + }
> > + }
> > +
> > + vdev->intf_devnode = media_devnode_create(vdev->v4l2_dev->mdev,
> > + intf_type,
> > + 0, VIDEO_MAJOR,
> > + vdev->minor,
> > + GFP_KERNEL);
> > + if (!vdev->intf_devnode) {
> > + media_device_unregister_entity(&vdev->entity);
> > + return -ENOMEM;
> > + }
> > +
> > + if (vdev->entity.type != MEDIA_ENT_T_UNKNOWN) {
> > + struct media_link *link;
> > +
> > + link = media_create_intf_link(&vdev->entity,
> > + &vdev->intf_devnode->intf, 0);
> > + if (!link) {
> > + media_devnode_remove(vdev->intf_devnode);
> > + media_device_unregister_entity(&vdev->entity);
> > + return -ENOMEM;
> > + }
> > + }
> > +
> > + /* FIXME: how to create the other interface links? */
>
> If they're needed (and I'm still not sure they are) they should be created by
> drivers, possibly with the help of helper functions.
>
> > +
> > +#endif
> > + return 0;
> > +}
> > +
> > /**
> > * __video_register_device - register video4linux devices
> > * @vdev: video device structure we want to register
> > @@ -908,22 +997,9 @@ int __video_register_device(struct video_device *vdev,
> > int type, int nr, /* Increase v4l2_device refcount */
> > v4l2_device_get(vdev->v4l2_dev);
> >
> > -#if defined(CONFIG_MEDIA_CONTROLLER)
> > /* Part 5: Register the entity. */
> > - if (vdev->v4l2_dev->mdev &&
> > - vdev->vfl_type != VFL_TYPE_SUBDEV) {
> > - vdev->entity.type = MEDIA_ENT_T_V4L2_VIDEO;
> > - vdev->entity.name = vdev->name;
> > - vdev->entity.info.dev.major = VIDEO_MAJOR;
> > - vdev->entity.info.dev.minor = vdev->minor;
> > - ret = media_device_register_entity(vdev->v4l2_dev->mdev,
> > - &vdev->entity);
> > - if (ret < 0)
> > - printk(KERN_WARNING
> > - "%s: media_device_register_entity failed\n",
> > - __func__);
> > - }
> > -#endif
> > + ret = video_register_media_controller(vdev, type);
> > +
> > /* Part 6: Activate this minor. The char device can now be used. */
> > set_bit(V4L2_FL_REGISTERED, &vdev->flags);
> >
> > diff --git a/drivers/media/v4l2-core/v4l2-device.c
> > b/drivers/media/v4l2-core/v4l2-device.c index 5b0a30b9252b..e788a085ba96
> > 100644
> > --- a/drivers/media/v4l2-core/v4l2-device.c
> > +++ b/drivers/media/v4l2-core/v4l2-device.c
> > @@ -249,6 +249,17 @@ int v4l2_device_register_subdev_nodes(struct
> > v4l2_device *v4l2_dev) #if defined(CONFIG_MEDIA_CONTROLLER)
> > sd->entity.info.dev.major = VIDEO_MAJOR;
> > sd->entity.info.dev.minor = vdev->minor;
> > +
> > + /* Interface is created by __video_register_device() */
> > + if (vdev->v4l2_dev->mdev) {
> > + struct media_link *link;
> > +
> > + link = media_create_intf_link(&sd->entity,
> > + &vdev->intf_devnode->intf,
> > + 0);
> > + if (!link)
> > + goto clean_up;
> > + }
> > #endif
> > sd->devnode = vdev;
> > }
> > @@ -285,7 +296,10 @@ void v4l2_device_unregister_subdev(struct v4l2_subdev
> > *sd)
> >
> > #if defined(CONFIG_MEDIA_CONTROLLER)
> > if (v4l2_dev->mdev) {
> > - media_entity_remove_links(&sd->entity);
> > + /*
> > + * No need to explicitly remove links, as both pads and
> > + * links are removed by the function below, in the right order
> > + */
> > media_device_unregister_entity(&sd->entity);
> > }
> > #endif
> > diff --git a/include/media/v4l2-dev.h b/include/media/v4l2-dev.h
> > index acbcd2f5fe7f..eeabf20e87a6 100644
> > --- a/include/media/v4l2-dev.h
> > +++ b/include/media/v4l2-dev.h
> > @@ -86,6 +86,7 @@ struct video_device
> > {
> > #if defined(CONFIG_MEDIA_CONTROLLER)
> > struct media_entity entity;
> > + struct media_intf_devnode *intf_devnode;
> > #endif
> > /* device ops */
> > const struct v4l2_file_operations *fops;
>
--
To unsubscribe from this list: send the line "unsubscribe linux-media" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
