Re: [PATCH 4/4] em28xx-v4l: get rid of field "users" in struct em28xx_v4l2

[Hans Verkuil <hverkuil@xs4all.nl>]

Hi Frank,

On 07/25/2014 07:48 PM, Frank Schäfer wrote:
> Instead of counting the number of opened file handles, use function
> v4l2_fh_is_singular_file() in em28xx_v4l2_open() and em28xx_v4l2_close() to
> determine if the file handle is the first/last opened one.

This won't work: if you capture from both /dev/video and /dev/vbi and close
one, then it stops all streaming.

I would just revert this patch completely.

There is currently no core support for detecting when all users of all devices
registered by a driver have left, so you don't have really have an alternative
but to use your old code.

Regards,

	Hans

> 
> Signed-off-by: Frank Schäfer <fschaefer.oss@googlemail.com>
> ---
>  drivers/media/usb/em28xx/em28xx-video.c | 23 +++++++++++++----------
>  drivers/media/usb/em28xx/em28xx.h       |  1 -
>  2 files changed, 13 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/media/usb/em28xx/em28xx-video.c b/drivers/media/usb/em28xx/em28xx-video.c
> index 3a7ec3b..087ccf9 100644
> --- a/drivers/media/usb/em28xx/em28xx-video.c
> +++ b/drivers/media/usb/em28xx/em28xx-video.c
> @@ -1883,9 +1883,8 @@ static int em28xx_v4l2_open(struct file *filp)
>  		return -EINVAL;
>  	}
>  
> -	em28xx_videodbg("open dev=%s type=%s users=%d\n",
> -			video_device_node_name(vdev), v4l2_type_names[fh_type],
> -			v4l2->users);
> +	em28xx_videodbg("open dev=%s type=%s\n",
> +			video_device_node_name(vdev), v4l2_type_names[fh_type]);
>  
>  	if (mutex_lock_interruptible(&dev->lock))
>  		return -ERESTARTSYS;
> @@ -1898,7 +1897,9 @@ static int em28xx_v4l2_open(struct file *filp)
>  		return ret;
>  	}
>  
> -	if (v4l2->users == 0) {
> +	if (v4l2_fh_is_singular_file(filp)) {
> +		em28xx_videodbg("first opened filehandle, initializing device\n");
> +
>  		em28xx_set_mode(dev, EM28XX_ANALOG_MODE);
>  
>  		if (vdev->vfl_type != VFL_TYPE_RADIO)
> @@ -1909,6 +1910,8 @@ static int em28xx_v4l2_open(struct file *filp)
>  		 * of some i2c devices
>  		 */
>  		em28xx_wake_i2c(dev);
> +	} else {
> +		em28xx_videodbg("further filehandles are already opened\n");
>  	}
>  
>  	if (vdev->vfl_type == VFL_TYPE_RADIO) {
> @@ -1918,7 +1921,6 @@ static int em28xx_v4l2_open(struct file *filp)
>  
>  	kref_get(&dev->ref);
>  	kref_get(&v4l2->ref);
> -	v4l2->users++;
>  
>  	mutex_unlock(&dev->lock);
>  
> @@ -2025,12 +2027,11 @@ static int em28xx_v4l2_close(struct file *filp)
>  	struct em28xx_v4l2    *v4l2 = dev->v4l2;
>  	int              errCode;
>  
> -	em28xx_videodbg("users=%d\n", v4l2->users);
> -
> -	vb2_fop_release(filp);
>  	mutex_lock(&dev->lock);
>  
> -	if (v4l2->users == 1) {
> +	if (v4l2_fh_is_singular_file(filp)) {
> +		em28xx_videodbg("last opened filehandle, shutting down device\n");
> +
>  		/* No sense to try to write to the device */
>  		if (dev->disconnected)
>  			goto exit;
> @@ -2049,10 +2050,12 @@ static int em28xx_v4l2_close(struct file *filp)
>  			em28xx_errdev("cannot change alternate number to "
>  					"0 (error=%i)\n", errCode);
>  		}
> +	} else {
> +		em28xx_videodbg("further opened filehandles left\n");
>  	}
>  
>  exit:
> -	v4l2->users--;
> +	vb2_fop_release(filp);
>  	kref_put(&v4l2->ref, em28xx_free_v4l2);
>  	mutex_unlock(&dev->lock);
>  	kref_put(&dev->ref, em28xx_free_device);
> diff --git a/drivers/media/usb/em28xx/em28xx.h b/drivers/media/usb/em28xx/em28xx.h
> index 4360338..84ef8ef 100644
> --- a/drivers/media/usb/em28xx/em28xx.h
> +++ b/drivers/media/usb/em28xx/em28xx.h
> @@ -524,7 +524,6 @@ struct em28xx_v4l2 {
>  	int sensor_yres;
>  	int sensor_xtal;
>  
> -	int users;		/* user count for exclusive use */
>  	int streaming_users;    /* number of actively streaming users */
>  
>  	u32 frequency;		/* selected tuner frequency */
>