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

["Frank Schäfer" <fschaefer.oss@googlemail.com>]

Hi Hans,

Am 18.09.2014 um 21:13 schrieb Hans Verkuil:
> 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.
You are 100% right, v4l2_fh_is_singular() is a per device _node_ check.
How could I miss that ? :/

> 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.
Indeed. I will send a revert patch.
Thanks for the hint !

Regards,
Frank


>
> 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 */
>>