Message-ID: <5422B1B8.1080401@xs4all.nl>
Date:	Wed, 24 Sep 2014 13:57:44 +0200
From:	Hans Verkuil <hverkuil@...all.nl>
To:	Shuah Khan <shuahkh@....samsung.com>, m.chehab@...sung.com,
	akpm@...ux-foundation.org, gregkh@...uxfoundation.org,
	crope@....fi, olebowle@....com, dheitmueller@...nellabs.co,
	ramakrmu@...co.com, sakari.ailus@...ux.intel.com,
	laurent.pinchart@...asonboard.com
CC:	linux-kernel@...r.kernel.org, linux-media@...r.kernel.org
Subject: Re: [PATCH 2/5] media: v4l2-core changes to use media tuner token
 api

Hi Shuah,

Here is my review...

On 09/22/2014 05:00 PM, Shuah Khan wrote:
> Changes to v4l2-core to hold tuner token in v4l2 ioctl that change
> the tuner modes, and reset the token from fh exit. The changes are
> limited to vb2 calls that disrupt digital stream. vb1 changes are
> made in the driver. The following ioctls are changed:
>
> S_INPUT, S_OUTPUT, S_FMT, S_TUNER, S_MODULATOR, S_FREQUENCY,

S_MODULATOR doesn't need to take a token. Certainly not a tuner token,
since it is a modulator, not a tuner. There aren't many modulator drivers,
and none of them have different modes.

The same is true for S_OUTPUT: it deals with outputs, so it has nothing
to do with tuners since those are for input.

> S_STD, S_HW_FREQ_SEEK:
>
> - hold tuner in shared analog mode before calling appropriate
>    ops->vidioc_s_*
> - return leaving tuner in shared mode.
> - Note that S_MODULATOR is now implemented in the core
>    previously FCN.
>
> QUERYSTD:
> - hold tuner in shared analog mode before calling
>    ops->vidioc_querystd
> - return after calling put tuner - this simply decrements the
>    owners. Leaves tuner in shared analog mode if owners > 0

I would handle QUERYSTD the same as the ones in the first group.
It's a fair assumption that once you call QUERYSTD you expect to
switch the tuner to analog mode and keep it there.

I'm missing STREAMON in this list as well.

With regards to G_TUNER and ENUM_INPUT, I will reply to the post that
discusses that topic.

>
> v4l2_fh_exit:
> - resets the media tuner token. A simple put token could leave
>    the token in shared mode. The nature of analog token holds
>    is unbalanced requiring a reset to clear it.

Nack on the reset. It should just put the tuner token.

The way it should work is that whenever an ioctl is issued that needs to
take a tuner token, then it should check if the filehandle already has a
token. If not, then take the token if possible. If it has, then check if
the token is in the right mode and continue if that's the case, otherwise
return EBUSY. I don't think it can ever be in the wrong mode, but it
doesn't hurt to check. Or do WARN_ON or something like that.

This way each filehandle will take a token only once, and it is released
when the filehandle is closed.

You do need to store in struct v4l2_fh whether or not a token was obtained
so the v4l2_fh_exit knows to release it.

Almost all drivers support v4l2_fh by now, so I wouldn't bother with drivers
that don't support v4l2_fh.

>
> Signed-off-by: Shuah Khan <shuahkh@....samsung.com>
> ---
>   drivers/media/v4l2-core/v4l2-fh.c    |   16 ++++++
>   drivers/media/v4l2-core/v4l2-ioctl.c |   96 +++++++++++++++++++++++++++++++++-
>   2 files changed, 110 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/media/v4l2-core/v4l2-fh.c b/drivers/media/v4l2-core/v4l2-fh.c
> index c97067a..81ce3f9 100644
> --- a/drivers/media/v4l2-core/v4l2-fh.c
> +++ b/drivers/media/v4l2-core/v4l2-fh.c
> @@ -25,7 +25,10 @@
>   #include <linux/bitops.h>
>   #include <linux/slab.h>
>   #include <linux/export.h>
> +#include <linux/device.h>
> +#include <linux/media_tknres.h>
>   #include <media/v4l2-dev.h>
> +#include <media/v4l2-device.h>
>   #include <media/v4l2-fh.h>
>   #include <media/v4l2-event.h>
>   #include <media/v4l2-ioctl.h>
> @@ -92,6 +95,19 @@ void v4l2_fh_exit(struct v4l2_fh *fh)
>   {
>   	if (fh->vdev == NULL)
>   		return;
> +
> +	if (fh->vdev->dev_parent) {
> +		enum media_tkn_mode mode;
> +
> +		mode = (fh->vdev->vfl_type == V4L2_TUNER_RADIO) ?
> +			MEDIA_MODE_RADIO : MEDIA_MODE_ANALOG;
> +		/* reset the token - the nature of token get in
> +		   analog mode is shared and unbalanced. There is
> +		   no clear start and stop, so shared token might
> +		   never get cleared */
> +		media_reset_shared_tuner_tkn(fh->vdev->dev_parent, mode);

As mentioned above, this should just be a put, not a reset.

> +	}
> +
>   	v4l2_event_unsubscribe_all(fh);
>   	fh->vdev = NULL;
>   }
> diff --git a/drivers/media/v4l2-core/v4l2-ioctl.c b/drivers/media/v4l2-core/v4l2-ioctl.c
> index d15e167..9e1f042 100644
> --- a/drivers/media/v4l2-core/v4l2-ioctl.c
> +++ b/drivers/media/v4l2-core/v4l2-ioctl.c
> @@ -17,6 +17,7 @@
>   #include <linux/types.h>
>   #include <linux/kernel.h>
>   #include <linux/version.h>
> +#include <linux/media_tknres.h>
>
>   #include <linux/videodev2.h>
>
> @@ -1003,6 +1004,37 @@ static void v4l_sanitize_format(struct v4l2_format *fmt)
>   	       sizeof(fmt->fmt.pix) - offset);
>   }
>
> +static int v4l_get_tuner_tkn(struct video_device *vfd,
> +				enum v4l2_tuner_type type)
> +{
> +	int ret = 0;
> +
> +	if (vfd->dev_parent) {
> +		enum media_tkn_mode mode;
> +
> +		mode = (type == V4L2_TUNER_RADIO) ?
> +			MEDIA_MODE_RADIO : MEDIA_MODE_ANALOG;
> +		ret = media_get_shared_tuner_tkn(vfd->dev_parent, mode);
> +		if (ret)
> +			dev_info(vfd->dev_parent,
> +				"%s: Tuner is busy\n", __func__);
> +	}
> +	dev_dbg(vfd->dev_parent, "%s: No token?? %d\n", __func__, ret);

Shouldn't this be in a 'else'? Now the 'No token' message is also printed when
media_get_shared_tuner_tkn got the tuner.

> +	return ret;
> +}
> +
> +static void v4l_put_tuner_tkn(struct video_device *vfd,
> +				enum v4l2_tuner_type type)
> +{
> +	if (vfd->dev_parent) {
> +		enum media_tkn_mode mode;
> +
> +		mode = (type == V4L2_TUNER_RADIO) ?
> +			MEDIA_MODE_RADIO : MEDIA_MODE_ANALOG;
> +		media_put_tuner_tkn(vfd->dev_parent, mode);
> +	}
> +}
> +
>   static int v4l_querycap(const struct v4l2_ioctl_ops *ops,
>   				struct file *file, void *fh, void *arg)
>   {
> @@ -1022,12 +1054,24 @@ static int v4l_querycap(const struct v4l2_ioctl_ops *ops,
>   static int v4l_s_input(const struct v4l2_ioctl_ops *ops,
>   				struct file *file, void *fh, void *arg)
>   {
> +	struct video_device *vfd = video_devdata(file);
> +	int ret = 0;
> +
> +	ret = v4l_get_tuner_tkn(vfd, V4L2_TUNER_ANALOG_TV);
> +	if (ret)
> +		return ret;
>   	return ops->vidioc_s_input(file, fh, *(unsigned int *)arg);
>   }
>
>   static int v4l_s_output(const struct v4l2_ioctl_ops *ops,
>   				struct file *file, void *fh, void *arg)
>   {
> +	struct video_device *vfd = video_devdata(file);
> +	int ret = 0;
> +
> +	ret = v4l_get_tuner_tkn(vfd, V4L2_TUNER_ANALOG_TV);
> +	if (ret)
> +		return ret;
>   	return ops->vidioc_s_output(file, fh, *(unsigned int *)arg);
>   }

As mentioned, tuner tokens make no sense for s_output.

>
> @@ -1236,6 +1280,10 @@ static int v4l_s_fmt(const struct v4l2_ioctl_ops *ops,
>   	bool is_tx = vfd->vfl_dir != VFL_DIR_RX;
>   	int ret;
>
> +	ret = v4l_get_tuner_tkn(vfd, V4L2_TUNER_ANALOG_TV);
> +	if (ret)
> +		return ret;
> +
>   	v4l_sanitize_format(p);
>
>   	switch (p->type) {
> @@ -1415,9 +1463,13 @@ static int v4l_s_tuner(const struct v4l2_ioctl_ops *ops,
>   {
>   	struct video_device *vfd = video_devdata(file);
>   	struct v4l2_tuner *p = arg;
> +	int ret;
>
>   	p->type = (vfd->vfl_type == VFL_TYPE_RADIO) ?
>   			V4L2_TUNER_RADIO : V4L2_TUNER_ANALOG_TV;
> +	ret = v4l_get_tuner_tkn(vfd, p->type);
> +	if (ret)
> +		return ret;
>   	return ops->vidioc_s_tuner(file, fh, p);
>   }
>
> @@ -1433,6 +1485,26 @@ static int v4l_g_modulator(const struct v4l2_ioctl_ops *ops,
>   	return err;
>   }
>
> +static int v4l_s_modulator(const struct v4l2_ioctl_ops *ops,
> +				struct file *file, void *fh, void *arg)
> +{
> +	struct video_device *vfd = video_devdata(file);
> +	struct v4l2_fh *vfh =
> +		test_bit(V4L2_FL_USES_V4L2_FH, &vfd->flags) ? fh : NULL;
> +
> +	if (vfh != NULL) {
> +		int ret;
> +		enum v4l2_tuner_type type;
> +
> +		type = (vfd->vfl_type == VFL_TYPE_RADIO) ?
> +				V4L2_TUNER_RADIO : V4L2_TUNER_ANALOG_TV;
> +		ret = v4l_get_tuner_tkn(vfd, type);
> +		if (ret)
> +			return ret;
> +	}
> +	return ops->vidioc_s_modulator(file, fh, arg);
> +}

Again, tuner tokens make no sense for a modulator.

> +
>   static int v4l_g_frequency(const struct v4l2_ioctl_ops *ops,
>   				struct file *file, void *fh, void *arg)
>   {
> @@ -1453,6 +1525,7 @@ static int v4l_s_frequency(const struct v4l2_ioctl_ops *ops,
>   	struct video_device *vfd = video_devdata(file);
>   	const struct v4l2_frequency *p = arg;
>   	enum v4l2_tuner_type type;
> +	int ret;
>
>   	if (vfd->vfl_type == VFL_TYPE_SDR) {
>   		if (p->type != V4L2_TUNER_ADC && p->type != V4L2_TUNER_RF)
> @@ -1462,6 +1535,9 @@ static int v4l_s_frequency(const struct v4l2_ioctl_ops *ops,
>   				V4L2_TUNER_RADIO : V4L2_TUNER_ANALOG_TV;
>   		if (type != p->type)
>   			return -EINVAL;
> +		ret = v4l_get_tuner_tkn(vfd, type);
> +		if (ret)
> +			return ret;
>   	}
>   	return ops->vidioc_s_frequency(file, fh, p);
>   }
> @@ -1508,11 +1584,16 @@ static int v4l_s_std(const struct v4l2_ioctl_ops *ops,
>   {
>   	struct video_device *vfd = video_devdata(file);
>   	v4l2_std_id id = *(v4l2_std_id *)arg, norm;
> +	int ret = 0;
>
>   	norm = id & vfd->tvnorms;
>   	if (vfd->tvnorms && !norm)	/* Check if std is supported */
>   		return -EINVAL;
>
> +	ret = v4l_get_tuner_tkn(vfd, V4L2_TUNER_ANALOG_TV);
> +	if (ret)
> +		return ret;
> +
>   	/* Calls the specific handler */
>   	return ops->vidioc_s_std(file, fh, norm);
>   }
> @@ -1522,7 +1603,11 @@ static int v4l_querystd(const struct v4l2_ioctl_ops *ops,
>   {
>   	struct video_device *vfd = video_devdata(file);
>   	v4l2_std_id *p = arg;
> +	int ret = 0;
>
> +	ret = v4l_get_tuner_tkn(vfd, V4L2_TUNER_ANALOG_TV);
> +	if (ret)
> +		return ret;
>   	/*
>   	 * If no signal is detected, then the driver should return
>   	 * V4L2_STD_UNKNOWN. Otherwise it should return tvnorms with
> @@ -1532,7 +1617,9 @@ static int v4l_querystd(const struct v4l2_ioctl_ops *ops,
>   	 * their efforts to improve the standards detection.
>   	 */
>   	*p = vfd->tvnorms;
> -	return ops->vidioc_querystd(file, fh, arg);
> +	ret = ops->vidioc_querystd(file, fh, arg);
> +	v4l_put_tuner_tkn(vfd, V4L2_TUNER_ANALOG_TV);

No put needed.

> +	return ret;
>   }
>
>   static int v4l_s_hw_freq_seek(const struct v4l2_ioctl_ops *ops,
> @@ -1541,6 +1628,7 @@ static int v4l_s_hw_freq_seek(const struct v4l2_ioctl_ops *ops,
>   	struct video_device *vfd = video_devdata(file);
>   	struct v4l2_hw_freq_seek *p = arg;
>   	enum v4l2_tuner_type type;
> +	int ret;
>
>   	/* s_hw_freq_seek is not supported for SDR for now */
>   	if (vfd->vfl_type == VFL_TYPE_SDR)
> @@ -1550,6 +1638,9 @@ static int v4l_s_hw_freq_seek(const struct v4l2_ioctl_ops *ops,
>   		V4L2_TUNER_RADIO : V4L2_TUNER_ANALOG_TV;
>   	if (p->type != type)
>   		return -EINVAL;
> +	ret = v4l_get_tuner_tkn(vfd, type);
> +	if (ret)
> +		return ret;
>   	return ops->vidioc_s_hw_freq_seek(file, fh, p);
>   }
>
> @@ -2217,7 +2308,8 @@ static struct v4l2_ioctl_info v4l2_ioctls[] = {
>   	IOCTL_INFO_STD(VIDIOC_G_AUDOUT, vidioc_g_audout, v4l_print_audioout, 0),
>   	IOCTL_INFO_STD(VIDIOC_S_AUDOUT, vidioc_s_audout, v4l_print_audioout, INFO_FL_PRIO),
>   	IOCTL_INFO_FNC(VIDIOC_G_MODULATOR, v4l_g_modulator, v4l_print_modulator, INFO_FL_CLEAR(v4l2_modulator, index)),
> -	IOCTL_INFO_STD(VIDIOC_S_MODULATOR, vidioc_s_modulator, v4l_print_modulator, INFO_FL_PRIO),
> +	IOCTL_INFO_FNC(VIDIOC_S_FREQUENCY, v4l_s_modulator,
> +			v4l_print_frequency, INFO_FL_PRIO),

Huh? S_MODULATOR is removed and a duplicate S_FREQUENCY is added?

>   	IOCTL_INFO_FNC(VIDIOC_G_FREQUENCY, v4l_g_frequency, v4l_print_frequency, INFO_FL_CLEAR(v4l2_frequency, tuner)),
>   	IOCTL_INFO_FNC(VIDIOC_S_FREQUENCY, v4l_s_frequency, v4l_print_frequency, INFO_FL_PRIO),
>   	IOCTL_INFO_FNC(VIDIOC_CROPCAP, v4l_cropcap, v4l_print_cropcap, INFO_FL_CLEAR(v4l2_cropcap, type)),
>

BTW, I still haven't seen how you are going to handle snd-usb-audio. I want to
see how that is going to be handled before I will Ack anything.

Regards,

	Hans
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