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* [PATCH] staging/vc04_services/bcm2835-camera: distinct numeration and names for devices
@ 2019-12-06  8:54 Michael Kupfer
  2020-01-10 13:25 ` Hans Verkuil
  0 siblings, 1 reply; 4+ messages in thread
From: Michael Kupfer @ 2019-12-06  8:54 UTC (permalink / raw)
  To: eric, wahrenst, bcm-kernel-feedback-list, linux-rpi-kernel,
	linux-arm-kernel, mchehab+samsung, hverkuil-cisco, linux-media
  Cc: devel, f.fainelli, Michael Kupfer, sbranden, linux-kernel,
	gregkh, linux-kernel, daniela.mormocea, dave.stevenson, rjui,
	Kay Friedrich

Create a static atomic counter for numerating cameras.
Use the Media Subsystem Kernel Internal API to create distinct
device-names, so that the camera-number (given by the counter)
matches the camera-name.

Co-developed-by: Kay Friedrich <kay.friedrich@fau.de>
Signed-off-by: Kay Friedrich <kay.friedrich@fau.de>
Signed-off-by: Michael Kupfer <michael.kupfer@fau.de>
---
 .../vc04_services/bcm2835-camera/bcm2835-camera.c        | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/drivers/staging/vc04_services/bcm2835-camera/bcm2835-camera.c b/drivers/staging/vc04_services/bcm2835-camera/bcm2835-camera.c
index beb6a0063bb8..be5f90a8b49d 100644
--- a/drivers/staging/vc04_services/bcm2835-camera/bcm2835-camera.c
+++ b/drivers/staging/vc04_services/bcm2835-camera/bcm2835-camera.c
@@ -60,6 +60,9 @@ MODULE_PARM_DESC(max_video_width, "Threshold for video mode");
 module_param(max_video_height, int, 0644);
 MODULE_PARM_DESC(max_video_height, "Threshold for video mode");
 
+/* camera instance counter */
+static atomic_t camera_instance = ATOMIC_INIT(0);
+
 /* global device data array */
 static struct bm2835_mmal_dev *gdev[MAX_BCM2835_CAMERAS];
 
@@ -1870,7 +1873,6 @@ static int bcm2835_mmal_probe(struct platform_device *pdev)
 
 		/* v4l2 core mutex used to protect all fops and v4l2 ioctls. */
 		mutex_init(&dev->mutex);
-		dev->camera_num = camera;
 		dev->max_width = resolutions[camera][0];
 		dev->max_height = resolutions[camera][1];
 
@@ -1886,8 +1888,9 @@ static int bcm2835_mmal_probe(struct platform_device *pdev)
 		dev->capture.fmt = &formats[3]; /* JPEG */
 
 		/* v4l device registration */
-		snprintf(dev->v4l2_dev.name, sizeof(dev->v4l2_dev.name),
-			 "%s", BM2835_MMAL_MODULE_NAME);
+		dev->camera_num = v4l2_device_set_name(&dev->v4l2_dev,
+						       BM2835_MMAL_MODULE_NAME,
+						       &camera_instance);
 		ret = v4l2_device_register(NULL, &dev->v4l2_dev);
 		if (ret) {
 			dev_err(&pdev->dev, "%s: could not register V4L2 device: %d\n",
-- 
2.20.1

_______________________________________________
devel mailing list
devel@linuxdriverproject.org
http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel

^ permalink raw reply	[flat|nested] 4+ messages in thread

* Re: [PATCH] staging/vc04_services/bcm2835-camera: distinct numeration and names for devices
  2019-12-06  8:54 [PATCH] staging/vc04_services/bcm2835-camera: distinct numeration and names for devices Michael Kupfer
@ 2020-01-10 13:25 ` Hans Verkuil
  2020-01-10 14:35   ` Dave Stevenson
  0 siblings, 1 reply; 4+ messages in thread
From: Hans Verkuil @ 2020-01-10 13:25 UTC (permalink / raw)
  To: Michael Kupfer, eric, wahrenst, bcm-kernel-feedback-list,
	linux-rpi-kernel, linux-arm-kernel, mchehab+samsung, linux-media
  Cc: devel, f.fainelli, Kay Friedrich, sbranden, linux-kernel, gregkh,
	linux-kernel, daniela.mormocea, dave.stevenson, rjui

Hi Michael, Kay,

On 12/6/19 9:54 AM, Michael Kupfer wrote:
> Create a static atomic counter for numerating cameras.
> Use the Media Subsystem Kernel Internal API to create distinct
> device-names, so that the camera-number (given by the counter)
> matches the camera-name.
> 
> Co-developed-by: Kay Friedrich <kay.friedrich@fau.de>
> Signed-off-by: Kay Friedrich <kay.friedrich@fau.de>
> Signed-off-by: Michael Kupfer <michael.kupfer@fau.de>
> ---
>  .../vc04_services/bcm2835-camera/bcm2835-camera.c        | 9 ++++++---
>  1 file changed, 6 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/staging/vc04_services/bcm2835-camera/bcm2835-camera.c b/drivers/staging/vc04_services/bcm2835-camera/bcm2835-camera.c
> index beb6a0063bb8..be5f90a8b49d 100644
> --- a/drivers/staging/vc04_services/bcm2835-camera/bcm2835-camera.c
> +++ b/drivers/staging/vc04_services/bcm2835-camera/bcm2835-camera.c
> @@ -60,6 +60,9 @@ MODULE_PARM_DESC(max_video_width, "Threshold for video mode");
>  module_param(max_video_height, int, 0644);
>  MODULE_PARM_DESC(max_video_height, "Threshold for video mode");
>  
> +/* camera instance counter */
> +static atomic_t camera_instance = ATOMIC_INIT(0);
> +
>  /* global device data array */
>  static struct bm2835_mmal_dev *gdev[MAX_BCM2835_CAMERAS];
>  
> @@ -1870,7 +1873,6 @@ static int bcm2835_mmal_probe(struct platform_device *pdev)
>  
>  		/* v4l2 core mutex used to protect all fops and v4l2 ioctls. */
>  		mutex_init(&dev->mutex);
> -		dev->camera_num = camera;
>  		dev->max_width = resolutions[camera][0];
>  		dev->max_height = resolutions[camera][1];
>  
> @@ -1886,8 +1888,9 @@ static int bcm2835_mmal_probe(struct platform_device *pdev)
>  		dev->capture.fmt = &formats[3]; /* JPEG */
>  
>  		/* v4l device registration */
> -		snprintf(dev->v4l2_dev.name, sizeof(dev->v4l2_dev.name),
> -			 "%s", BM2835_MMAL_MODULE_NAME);
> +		dev->camera_num = v4l2_device_set_name(&dev->v4l2_dev,
> +						       BM2835_MMAL_MODULE_NAME,
> +						       &camera_instance);
>  		ret = v4l2_device_register(NULL, &dev->v4l2_dev);
>  		if (ret) {
>  			dev_err(&pdev->dev, "%s: could not register V4L2 device: %d\n",
> 

Actually, in this specific case I would not use v4l2_device_set_name().

Instead just use:

		snprintf(dev->v4l2_dev.name, sizeof(dev->v4l2_dev.name),
			 "%s-%u", BM2835_MMAL_MODULE_NAME, camera);

It would be even better if there would be just one top-level v4l2_device used
for all the camera instances. After all, there really is just one platform
device for all of the cameras, and I would expect to see just a single
v4l2_device as well.

It doesn't hurt to have multiple v4l2_device structs, but it introduces a
slight memory overhead since one would have been sufficient.

v4l2_device_set_name() is meant for pci-like devices. And it really
is a bit overkill to have it as a helper function.

Regards,

	Hans
_______________________________________________
devel mailing list
devel@linuxdriverproject.org
http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel

^ permalink raw reply	[flat|nested] 4+ messages in thread

* Re: [PATCH] staging/vc04_services/bcm2835-camera: distinct numeration and names for devices
  2020-01-10 13:25 ` Hans Verkuil
@ 2020-01-10 14:35   ` Dave Stevenson
  2020-01-10 14:49     ` Hans Verkuil
  0 siblings, 1 reply; 4+ messages in thread
From: Dave Stevenson @ 2020-01-10 14:35 UTC (permalink / raw)
  To: Hans Verkuil
  Cc: devel, f.fainelli, sbranden, Michael Kupfer, linux-kernel,
	gregkh, linux-kernel, eric, daniela.mormocea,
	bcm-kernel-feedback-list, wahrenst, Dave Stevenson, rjui,
	mchehab+samsung, linux-media, Kay Friedrich, linux-arm-kernel,
	linux-rpi-kernel

Hi Hans

On Fri, 10 Jan 2020 at 13:25, Hans Verkuil <hverkuil-cisco@xs4all.nl> wrote:
>
> Hi Michael, Kay,
>
> On 12/6/19 9:54 AM, Michael Kupfer wrote:
> > Create a static atomic counter for numerating cameras.
> > Use the Media Subsystem Kernel Internal API to create distinct
> > device-names, so that the camera-number (given by the counter)
> > matches the camera-name.
> >
> > Co-developed-by: Kay Friedrich <kay.friedrich@fau.de>
> > Signed-off-by: Kay Friedrich <kay.friedrich@fau.de>
> > Signed-off-by: Michael Kupfer <michael.kupfer@fau.de>
> > ---
> >  .../vc04_services/bcm2835-camera/bcm2835-camera.c        | 9 ++++++---
> >  1 file changed, 6 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/staging/vc04_services/bcm2835-camera/bcm2835-camera.c b/drivers/staging/vc04_services/bcm2835-camera/bcm2835-camera.c
> > index beb6a0063bb8..be5f90a8b49d 100644
> > --- a/drivers/staging/vc04_services/bcm2835-camera/bcm2835-camera.c
> > +++ b/drivers/staging/vc04_services/bcm2835-camera/bcm2835-camera.c
> > @@ -60,6 +60,9 @@ MODULE_PARM_DESC(max_video_width, "Threshold for video mode");
> >  module_param(max_video_height, int, 0644);
> >  MODULE_PARM_DESC(max_video_height, "Threshold for video mode");
> >
> > +/* camera instance counter */
> > +static atomic_t camera_instance = ATOMIC_INIT(0);
> > +
> >  /* global device data array */
> >  static struct bm2835_mmal_dev *gdev[MAX_BCM2835_CAMERAS];
> >
> > @@ -1870,7 +1873,6 @@ static int bcm2835_mmal_probe(struct platform_device *pdev)
> >
> >               /* v4l2 core mutex used to protect all fops and v4l2 ioctls. */
> >               mutex_init(&dev->mutex);
> > -             dev->camera_num = camera;
> >               dev->max_width = resolutions[camera][0];
> >               dev->max_height = resolutions[camera][1];
> >
> > @@ -1886,8 +1888,9 @@ static int bcm2835_mmal_probe(struct platform_device *pdev)
> >               dev->capture.fmt = &formats[3]; /* JPEG */
> >
> >               /* v4l device registration */
> > -             snprintf(dev->v4l2_dev.name, sizeof(dev->v4l2_dev.name),
> > -                      "%s", BM2835_MMAL_MODULE_NAME);
> > +             dev->camera_num = v4l2_device_set_name(&dev->v4l2_dev,
> > +                                                    BM2835_MMAL_MODULE_NAME,
> > +                                                    &camera_instance);
> >               ret = v4l2_device_register(NULL, &dev->v4l2_dev);
> >               if (ret) {
> >                       dev_err(&pdev->dev, "%s: could not register V4L2 device: %d\n",
> >
>
> Actually, in this specific case I would not use v4l2_device_set_name().
>
> Instead just use:
>
>                 snprintf(dev->v4l2_dev.name, sizeof(dev->v4l2_dev.name),
>                          "%s-%u", BM2835_MMAL_MODULE_NAME, camera);
>
> It would be even better if there would be just one top-level v4l2_device used
> for all the camera instances. After all, there really is just one platform
> device for all of the cameras, and I would expect to see just a single
> v4l2_device as well.
>
> It doesn't hurt to have multiple v4l2_device structs, but it introduces a
> slight memory overhead since one would have been sufficient.

Doesn't that make all controls for all cameras common? The struct
v4l2_ctrl_handler is part of struct v4l2_device.

Or do we:
- ditch the use of ctrl_handler in struct v4l2_device
- create and initialise a ctrl_handler per camera on an internal
structure so we retain the control state
- assign ctrl_handler in struct v4l2_fh to it every time a file handle
on the device is opened?

And if we only have one struct v4l2_device then is there the
possibility of the unique names that Michael and Kay are trying to
introduce?

I'm a little confused as to whether there really is a gain in having a
single v4l2_device. In this case the two cameras are independent
devices, even if they are loaded by a single platform driver.

  Dave

> v4l2_device_set_name() is meant for pci-like devices. And it really
> is a bit overkill to have it as a helper function.
>
> Regards,
>
>         Hans
_______________________________________________
devel mailing list
devel@linuxdriverproject.org
http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel

^ permalink raw reply	[flat|nested] 4+ messages in thread

* Re: [PATCH] staging/vc04_services/bcm2835-camera: distinct numeration and names for devices
  2020-01-10 14:35   ` Dave Stevenson
@ 2020-01-10 14:49     ` Hans Verkuil
  0 siblings, 0 replies; 4+ messages in thread
From: Hans Verkuil @ 2020-01-10 14:49 UTC (permalink / raw)
  To: Dave Stevenson
  Cc: devel, f.fainelli, sbranden, Michael Kupfer, linux-kernel,
	gregkh, linux-kernel, eric, daniela.mormocea,
	bcm-kernel-feedback-list, wahrenst, Dave Stevenson, rjui,
	mchehab+samsung, linux-media, Kay Friedrich, linux-arm-kernel,
	linux-rpi-kernel

On 1/10/20 3:35 PM, Dave Stevenson wrote:
> Hi Hans
> 
> On Fri, 10 Jan 2020 at 13:25, Hans Verkuil <hverkuil-cisco@xs4all.nl> wrote:
>>
>> Hi Michael, Kay,
>>
>> On 12/6/19 9:54 AM, Michael Kupfer wrote:
>>> Create a static atomic counter for numerating cameras.
>>> Use the Media Subsystem Kernel Internal API to create distinct
>>> device-names, so that the camera-number (given by the counter)
>>> matches the camera-name.
>>>
>>> Co-developed-by: Kay Friedrich <kay.friedrich@fau.de>
>>> Signed-off-by: Kay Friedrich <kay.friedrich@fau.de>
>>> Signed-off-by: Michael Kupfer <michael.kupfer@fau.de>
>>> ---
>>>  .../vc04_services/bcm2835-camera/bcm2835-camera.c        | 9 ++++++---
>>>  1 file changed, 6 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/drivers/staging/vc04_services/bcm2835-camera/bcm2835-camera.c b/drivers/staging/vc04_services/bcm2835-camera/bcm2835-camera.c
>>> index beb6a0063bb8..be5f90a8b49d 100644
>>> --- a/drivers/staging/vc04_services/bcm2835-camera/bcm2835-camera.c
>>> +++ b/drivers/staging/vc04_services/bcm2835-camera/bcm2835-camera.c
>>> @@ -60,6 +60,9 @@ MODULE_PARM_DESC(max_video_width, "Threshold for video mode");
>>>  module_param(max_video_height, int, 0644);
>>>  MODULE_PARM_DESC(max_video_height, "Threshold for video mode");
>>>
>>> +/* camera instance counter */
>>> +static atomic_t camera_instance = ATOMIC_INIT(0);
>>> +
>>>  /* global device data array */
>>>  static struct bm2835_mmal_dev *gdev[MAX_BCM2835_CAMERAS];
>>>
>>> @@ -1870,7 +1873,6 @@ static int bcm2835_mmal_probe(struct platform_device *pdev)
>>>
>>>               /* v4l2 core mutex used to protect all fops and v4l2 ioctls. */
>>>               mutex_init(&dev->mutex);
>>> -             dev->camera_num = camera;
>>>               dev->max_width = resolutions[camera][0];
>>>               dev->max_height = resolutions[camera][1];
>>>
>>> @@ -1886,8 +1888,9 @@ static int bcm2835_mmal_probe(struct platform_device *pdev)
>>>               dev->capture.fmt = &formats[3]; /* JPEG */
>>>
>>>               /* v4l device registration */
>>> -             snprintf(dev->v4l2_dev.name, sizeof(dev->v4l2_dev.name),
>>> -                      "%s", BM2835_MMAL_MODULE_NAME);
>>> +             dev->camera_num = v4l2_device_set_name(&dev->v4l2_dev,
>>> +                                                    BM2835_MMAL_MODULE_NAME,
>>> +                                                    &camera_instance);
>>>               ret = v4l2_device_register(NULL, &dev->v4l2_dev);
>>>               if (ret) {
>>>                       dev_err(&pdev->dev, "%s: could not register V4L2 device: %d\n",
>>>
>>
>> Actually, in this specific case I would not use v4l2_device_set_name().
>>
>> Instead just use:
>>
>>                 snprintf(dev->v4l2_dev.name, sizeof(dev->v4l2_dev.name),
>>                          "%s-%u", BM2835_MMAL_MODULE_NAME, camera);
>>
>> It would be even better if there would be just one top-level v4l2_device used
>> for all the camera instances. After all, there really is just one platform
>> device for all of the cameras, and I would expect to see just a single
>> v4l2_device as well.
>>
>> It doesn't hurt to have multiple v4l2_device structs, but it introduces a
>> slight memory overhead since one would have been sufficient.
> 
> Doesn't that make all controls for all cameras common? The struct
> v4l2_ctrl_handler is part of struct v4l2_device.
> 
> Or do we:
> - ditch the use of ctrl_handler in struct v4l2_device
> - create and initialise a ctrl_handler per camera on an internal
> structure so we retain the control state
> - assign ctrl_handler in struct v4l2_fh to it every time a file handle
> on the device is opened?

You can set ctrl_handlers at three levels: v4l2_device (common to all
video devices), video_device (specific to a single video device), or
for v4l2_fh (specific to that filehandle only).

In this case you would assign it to the video_device:

	dev->vdev.ctrl_handler = &dev->ctrl_handler;

> 
> And if we only have one struct v4l2_device then is there the
> possibility of the unique names that Michael and Kay are trying to
> introduce?
> 
> I'm a little confused as to whether there really is a gain in having a
> single v4l2_device. In this case the two cameras are independent
> devices, even if they are loaded by a single platform driver.

There probably is little to no gain. Hence my proposal to just stick the
camera index after the module name.

Regards,

	Hans

> 
>   Dave
> 
>> v4l2_device_set_name() is meant for pci-like devices. And it really
>> is a bit overkill to have it as a helper function.
>>
>> Regards,
>>
>>         Hans

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devel mailing list
devel@linuxdriverproject.org
http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel

^ permalink raw reply	[flat|nested] 4+ messages in thread

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Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2019-12-06  8:54 [PATCH] staging/vc04_services/bcm2835-camera: distinct numeration and names for devices Michael Kupfer
2020-01-10 13:25 ` Hans Verkuil
2020-01-10 14:35   ` Dave Stevenson
2020-01-10 14:49     ` Hans Verkuil

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