[PATCH] v4l: Build error with et61x251, if V4L1_COMPAT is not selected

[PATCH] v4l: Build error with et61x251, if V4L1_COMPAT is not selected

[aherrman]

With current git tree I get an build error
for et61x251, if V4L1_COMPAT is not selected:

drivers/media/video/et61x251/et61x251_core.c: In et61x251_show_:
drivers/media/video/et61x251/et61x251_core.c:718: error: implicit declaration of to_video_device

Fix: add VIDEO_V4L1_COMPAT as a dependency for this driver.

Signed-off-by: Andreas Herrmann <aherrman@arcor.de>
---
 drivers/media/video/et61x251/Kconfig |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/drivers/media/video/et61x251/Kconfig b/drivers/media/video/et61x251/Kconfig
index dcc1a03..9143424 100644
--- a/drivers/media/video/et61x251/Kconfig
+++ b/drivers/media/video/et61x251/Kconfig
@@ -1,6 +1,6 @@
 config USB_ET61X251
 	tristate "USB ET61X[12]51 PC Camera Controller support"
-	depends on VIDEO_V4L2
+	depends on VIDEO_V4L2 && VIDEO_V4L1_COMPAT
 	---help---
 	  Say Y here if you want support for cameras based on Etoms ET61X151
 	  or ET61X251 PC Camera Controllers.
-- 
1.5.3

Re: [PATCH] v4l: Build error with et61x251, if V4L1_COMPAT is not selected

[Luca Risolia]

On Thursday 13 September 2007 14:36:27 aherrman@arcor.de wrote:
> With current git tree I get an build error
> for et61x251, if V4L1_COMPAT is not selected:
>
> drivers/media/video/et61x251/et61x251_core.c: In et61x251_show_:
> drivers/media/video/et61x251/et61x251_core.c:718: error: implicit
> declaration of to_video_device
>
> Fix: add VIDEO_V4L1_COMPAT as a dependency for this driver.

No, wait. The driver really is V4L2 only. If you can, please fix it by 
replacing to_video_device() with container_of() instead:

cam = video_get_drvdata(container_of(cd, struct video_device, class_dev));

Best regards
Luca Risolia

>
> Signed-off-by: Andreas Herrmann <aherrman@arcor.de>
> ---
>  drivers/media/video/et61x251/Kconfig |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
>
> diff --git a/drivers/media/video/et61x251/Kconfig
> b/drivers/media/video/et61x251/Kconfig index dcc1a03..9143424 100644
> --- a/drivers/media/video/et61x251/Kconfig
> +++ b/drivers/media/video/et61x251/Kconfig
> @@ -1,6 +1,6 @@
>  config USB_ET61X251
>  	tristate "USB ET61X[12]51 PC Camera Controller support"
> -	depends on VIDEO_V4L2
> +	depends on VIDEO_V4L2 && VIDEO_V4L1_COMPAT
>  	---help---
>  	  Say Y here if you want support for cameras based on Etoms ET61X151
>  	  or ET61X251 PC Camera Controllers.

Re: [PATCH] v4l: Build error with et61x251, if V4L1_COMPAT is not selected

[aherrman]

On Thu, Sep 13, 2007 at 05:07:16PM +0200, Luca Risolia wrote:
> On Thursday 13 September 2007 14:36:27 aherrman@arcor.de wrote:
> > With current git tree I get an build error
> > for et61x251, if V4L1_COMPAT is not selected:
> >
> > drivers/media/video/et61x251/et61x251_core.c: In et61x251_show_:
> > drivers/media/video/et61x251/et61x251_core.c:718: error: implicit
> > declaration of to_video_device
> >
> > Fix: add VIDEO_V4L1_COMPAT as a dependency for this driver.
> 
> No, wait. The driver really is V4L2 only. If you can, please fix it by 
> replacing to_video_device() with container_of() instead:
> 
> cam = video_get_drvdata(container_of(cd, struct video_device, class_dev));

Ah just some v4l1 remainders.
I'll do that.


Regards,

Andreas

[PATCH] v4l: fix build error for et61x251 driver

[Andreas Herrmann]

This fixes a kernel build problem and
should make it into 2.6.23, I think.


Regards,

Andreas

--

Get rid of some v4l1 remainders to avoid kernel build errors if
V4L1_COMPAT is not selected:

  drivers/media/video/et61x251/et61x251_core.c: In et61x251_show_:
  drivers/media/video/et61x251/et61x251_core.c:718: error: implicit
    declaration of to_video_device

Fix as suggested by  Luca Risolia <luca.risolia@studio.unibo.it>

Signed-off-by: Andreas Herrmann <aherrman@arcor.de>
---
 drivers/media/video/et61x251/et61x251_core.c |   24 ++++++++++++++++--------
 1 files changed, 16 insertions(+), 8 deletions(-)

diff --git a/drivers/media/video/et61x251/et61x251_core.c b/drivers/media/video/et61x251/et61x251_core.c
index 585bd1f..a3ee968 100644
--- a/drivers/media/video/et61x251/et61x251_core.c
+++ b/drivers/media/video/et61x251/et61x251_core.c
@@ -715,7 +715,8 @@ static ssize_t et61x251_show_reg(struct class_device* cd, char* buf)
 	if (mutex_lock_interruptible(&et61x251_sysfs_lock))
 		return -ERESTARTSYS;
 
-	cam = video_get_drvdata(to_video_device(cd));
+	cam = video_get_drvdata(container_of(cd, struct video_device,
+					     class_dev));
 	if (!cam) {
 		mutex_unlock(&et61x251_sysfs_lock);
 		return -ENODEV;
@@ -739,7 +740,8 @@ et61x251_store_reg(struct class_device* cd, const char* buf, size_t len)
 	if (mutex_lock_interruptible(&et61x251_sysfs_lock))
 		return -ERESTARTSYS;
 
-	cam = video_get_drvdata(to_video_device(cd));
+	cam = video_get_drvdata(container_of(cd, struct video_device,
+					     class_dev));
 	if (!cam) {
 		mutex_unlock(&et61x251_sysfs_lock);
 		return -ENODEV;
@@ -771,7 +773,8 @@ static ssize_t et61x251_show_val(struct class_device* cd, char* buf)
 	if (mutex_lock_interruptible(&et61x251_sysfs_lock))
 		return -ERESTARTSYS;
 
-	cam = video_get_drvdata(to_video_device(cd));
+	cam = video_get_drvdata(container_of(cd, struct video_device,
+					     class_dev));
 	if (!cam) {
 		mutex_unlock(&et61x251_sysfs_lock);
 		return -ENODEV;
@@ -803,7 +806,8 @@ et61x251_store_val(struct class_device* cd, const char* buf, size_t len)
 	if (mutex_lock_interruptible(&et61x251_sysfs_lock))
 		return -ERESTARTSYS;
 
-	cam = video_get_drvdata(to_video_device(cd));
+	cam = video_get_drvdata(container_of(cd, struct video_device,
+					     class_dev));
 	if (!cam) {
 		mutex_unlock(&et61x251_sysfs_lock);
 		return -ENODEV;
@@ -839,7 +843,8 @@ static ssize_t et61x251_show_i2c_reg(struct class_device* cd, char* buf)
 	if (mutex_lock_interruptible(&et61x251_sysfs_lock))
 		return -ERESTARTSYS;
 
-	cam = video_get_drvdata(to_video_device(cd));
+	cam = video_get_drvdata(container_of(cd, struct video_device,
+					     class_dev));
 	if (!cam) {
 		mutex_unlock(&et61x251_sysfs_lock);
 		return -ENODEV;
@@ -865,7 +870,8 @@ et61x251_store_i2c_reg(struct class_device* cd, const char* buf, size_t len)
 	if (mutex_lock_interruptible(&et61x251_sysfs_lock))
 		return -ERESTARTSYS;
 
-	cam = video_get_drvdata(to_video_device(cd));
+	cam = video_get_drvdata(container_of(cd, struct video_device,
+					     class_dev));
 	if (!cam) {
 		mutex_unlock(&et61x251_sysfs_lock);
 		return -ENODEV;
@@ -897,7 +903,8 @@ static ssize_t et61x251_show_i2c_val(struct class_device* cd, char* buf)
 	if (mutex_lock_interruptible(&et61x251_sysfs_lock))
 		return -ERESTARTSYS;
 
-	cam = video_get_drvdata(to_video_device(cd));
+	cam = video_get_drvdata(container_of(cd, struct video_device,
+					     class_dev));
 	if (!cam) {
 		mutex_unlock(&et61x251_sysfs_lock);
 		return -ENODEV;
@@ -934,7 +941,8 @@ et61x251_store_i2c_val(struct class_device* cd, const char* buf, size_t len)
 	if (mutex_lock_interruptible(&et61x251_sysfs_lock))
 		return -ERESTARTSYS;
 
-	cam = video_get_drvdata(to_video_device(cd));
+	cam = video_get_drvdata(container_of(cd, struct video_device,
+					     class_dev));
 	if (!cam) {
 		mutex_unlock(&et61x251_sysfs_lock);
 		return -ENODEV;
-- 
1.5.3

Re: [PATCH] v4l: fix build error for et61x251 driver

[Luca Risolia]

Hacked-by: Luca Risolia <luca.risolia@studio.unibo.it>

On Friday 14 September 2007 00:27:17 Andreas Herrmann wrote:
> This fixes a kernel build problem and
> should make it into 2.6.23, I think.
>
>
> Regards,
>
> Andreas
>
> --
>
> Get rid of some v4l1 remainders to avoid kernel build errors if
> V4L1_COMPAT is not selected:
>
>   drivers/media/video/et61x251/et61x251_core.c: In et61x251_show_:
>   drivers/media/video/et61x251/et61x251_core.c:718: error: implicit
>     declaration of to_video_device
>
> Fix as suggested by  Luca Risolia <luca.risolia@studio.unibo.it>
>
> Signed-off-by: Andreas Herrmann <aherrman@arcor.de>
> ---
>  drivers/media/video/et61x251/et61x251_core.c |   24
> ++++++++++++++++-------- 1 files changed, 16 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/media/video/et61x251/et61x251_core.c
> b/drivers/media/video/et61x251/et61x251_core.c index 585bd1f..a3ee968
> 100644
> --- a/drivers/media/video/et61x251/et61x251_core.c
> +++ b/drivers/media/video/et61x251/et61x251_core.c
> @@ -715,7 +715,8 @@ static ssize_t et61x251_show_reg(struct class_device*
> cd, char* buf) if (mutex_lock_interruptible(&et61x251_sysfs_lock))
>  		return -ERESTARTSYS;
>
> -	cam = video_get_drvdata(to_video_device(cd));
> +	cam = video_get_drvdata(container_of(cd, struct video_device,
> +					     class_dev));
>  	if (!cam) {
>  		mutex_unlock(&et61x251_sysfs_lock);
>  		return -ENODEV;
> @@ -739,7 +740,8 @@ et61x251_store_reg(struct class_device* cd, const char*
> buf, size_t len) if (mutex_lock_interruptible(&et61x251_sysfs_lock))
>  		return -ERESTARTSYS;
>
> -	cam = video_get_drvdata(to_video_device(cd));
> +	cam = video_get_drvdata(container_of(cd, struct video_device,
> +					     class_dev));
>  	if (!cam) {
>  		mutex_unlock(&et61x251_sysfs_lock);
>  		return -ENODEV;
> @@ -771,7 +773,8 @@ static ssize_t et61x251_show_val(struct class_device*
> cd, char* buf) if (mutex_lock_interruptible(&et61x251_sysfs_lock))
>  		return -ERESTARTSYS;
>
> -	cam = video_get_drvdata(to_video_device(cd));
> +	cam = video_get_drvdata(container_of(cd, struct video_device,
> +					     class_dev));
>  	if (!cam) {
>  		mutex_unlock(&et61x251_sysfs_lock);
>  		return -ENODEV;
> @@ -803,7 +806,8 @@ et61x251_store_val(struct class_device* cd, const char*
> buf, size_t len) if (mutex_lock_interruptible(&et61x251_sysfs_lock))
>  		return -ERESTARTSYS;
>
> -	cam = video_get_drvdata(to_video_device(cd));
> +	cam = video_get_drvdata(container_of(cd, struct video_device,
> +					     class_dev));
>  	if (!cam) {
>  		mutex_unlock(&et61x251_sysfs_lock);
>  		return -ENODEV;
> @@ -839,7 +843,8 @@ static ssize_t et61x251_show_i2c_reg(struct
> class_device* cd, char* buf) if
> (mutex_lock_interruptible(&et61x251_sysfs_lock))
>  		return -ERESTARTSYS;
>
> -	cam = video_get_drvdata(to_video_device(cd));
> +	cam = video_get_drvdata(container_of(cd, struct video_device,
> +					     class_dev));
>  	if (!cam) {
>  		mutex_unlock(&et61x251_sysfs_lock);
>  		return -ENODEV;
> @@ -865,7 +870,8 @@ et61x251_store_i2c_reg(struct class_device* cd, const
> char* buf, size_t len) if (mutex_lock_interruptible(&et61x251_sysfs_lock))
>  		return -ERESTARTSYS;
>
> -	cam = video_get_drvdata(to_video_device(cd));
> +	cam = video_get_drvdata(container_of(cd, struct video_device,
> +					     class_dev));
>  	if (!cam) {
>  		mutex_unlock(&et61x251_sysfs_lock);
>  		return -ENODEV;
> @@ -897,7 +903,8 @@ static ssize_t et61x251_show_i2c_val(struct
> class_device* cd, char* buf) if
> (mutex_lock_interruptible(&et61x251_sysfs_lock))
>  		return -ERESTARTSYS;
>
> -	cam = video_get_drvdata(to_video_device(cd));
> +	cam = video_get_drvdata(container_of(cd, struct video_device,
> +					     class_dev));
>  	if (!cam) {
>  		mutex_unlock(&et61x251_sysfs_lock);
>  		return -ENODEV;
> @@ -934,7 +941,8 @@ et61x251_store_i2c_val(struct class_device* cd, const
> char* buf, size_t len) if (mutex_lock_interruptible(&et61x251_sysfs_lock))
>  		return -ERESTARTSYS;
>
> -	cam = video_get_drvdata(to_video_device(cd));
> +	cam = video_get_drvdata(container_of(cd, struct video_device,
> +					     class_dev));
>  	if (!cam) {
>  		mutex_unlock(&et61x251_sysfs_lock);
>  		return -ENODEV;

Re: [PATCH] v4l: fix build error for et61x251 driver

[Linus Torvalds]

On Fri, 14 Sep 2007, Luca Risolia wrote:

> Hacked-by: Luca Risolia <luca.risolia@studio.unibo.it>
> 
> On Friday 14 September 2007 00:27:17 Andreas Herrmann wrote:
> > This fixes a kernel build problem and
> > should make it into 2.6.23, I think.
> >
> >
> > Regards,
> >
> > Andreas
> >
> > --
> >
> > Get rid of some v4l1 remainders to avoid kernel build errors if
> > V4L1_COMPAT is not selected:
> >
> >   drivers/media/video/et61x251/et61x251_core.c: In et61x251_show_:
> >   drivers/media/video/et61x251/et61x251_core.c:718: error: implicit
> >     declaration of to_video_device
> >
> > Fix as suggested by  Luca Risolia <luca.risolia@studio.unibo.it>

This patch is really ugly.

Why can't the "to_video_device()" macro be used? Just move it to a place 
where it's usable! IOW, what's wrong with the *much* simpler patch below?

That "to_video_device()" macro has absolutely _nothing_ to do with 
CONFIG_VIDEO_V4L1_COMPAT, as far as I can tell!

			Linus
---
diff --git a/include/media/v4l2-dev.h b/include/media/v4l2-dev.h
index d62847f..17f8f3a 100644
--- a/include/media/v4l2-dev.h
+++ b/include/media/v4l2-dev.h
@@ -337,6 +337,9 @@ void *priv;
 	struct class_device class_dev; /* sysfs */
 };
 
+/* Class-dev to video-device */
+#define to_video_device(cd) container_of(cd, struct video_device, class_dev)
+
 /* Version 2 functions */
 extern int video_register_device(struct video_device *vfd, int type, int nr);
 void video_unregister_device(struct video_device *);
@@ -354,11 +357,9 @@ extern int video_usercopy(struct inode *inode, struct file *file,
 			  int (*func)(struct inode *inode, struct file *file,
 				      unsigned int cmd, void *arg));
 
-
 #ifdef CONFIG_VIDEO_V4L1_COMPAT
 #include <linux/mm.h>
 
-#define to_video_device(cd) container_of(cd, struct video_device, class_dev)
 static inline int __must_check
 video_device_create_file(struct video_device *vfd,
 			 struct class_device_attribute *attr)

Re: [PATCH] v4l: fix build error for et61x251 driver

[Luca Risolia]

On Friday 14 September 2007 02:09:01 Linus Torvalds wrote:
> On Fri, 14 Sep 2007, Luca Risolia wrote:
> > Hacked-by: Luca Risolia <luca.risolia@studio.unibo.it>
> >
> > On Friday 14 September 2007 00:27:17 Andreas Herrmann wrote:
> > > This fixes a kernel build problem and
> > > should make it into 2.6.23, I think.
> > >
> > >
> > > Regards,
> > >
> > > Andreas
> > >
> > > --
> > >
> > > Get rid of some v4l1 remainders to avoid kernel build errors if
> > > V4L1_COMPAT is not selected:
> > >
> > >   drivers/media/video/et61x251/et61x251_core.c: In et61x251_show_:
> > >   drivers/media/video/et61x251/et61x251_core.c:718: error: implicit
> > >     declaration of to_video_device
> > >
> > > Fix as suggested by  Luca Risolia <luca.risolia@studio.unibo.it>
>
> This patch is really ugly.
>
> Why can't the "to_video_device()" macro be used? Just move it to a place
> where it's usable! IOW, what's wrong with the *much* simpler patch below?

There's nothing wtong in my opinion. I do not know the exact reason why Mauro 
moved "to_video_device()" into CONFIG_VIDEO_V4L1_COMPAT. Pheraps he can give 
more details about this change.


> That "to_video_device()" macro has absolutely _nothing_ to do with
> CONFIG_VIDEO_V4L1_COMPAT, as far as I can tell!
>
> 			Linus
> ---
> diff --git a/include/media/v4l2-dev.h b/include/media/v4l2-dev.h
> index d62847f..17f8f3a 100644
> --- a/include/media/v4l2-dev.h
> +++ b/include/media/v4l2-dev.h
> @@ -337,6 +337,9 @@ void *priv;
>  	struct class_device class_dev; /* sysfs */
>  };
>
> +/* Class-dev to video-device */
> +#define to_video_device(cd) container_of(cd, struct video_device,
> class_dev) +
>  /* Version 2 functions */
>  extern int video_register_device(struct video_device *vfd, int type, int
> nr); void video_unregister_device(struct video_device *);
> @@ -354,11 +357,9 @@ extern int video_usercopy(struct inode *inode, struct
> file *file, int (*func)(struct inode *inode, struct file *file,
>  				      unsigned int cmd, void *arg));
>
> -
>  #ifdef CONFIG_VIDEO_V4L1_COMPAT
>  #include <linux/mm.h>
>
> -#define to_video_device(cd) container_of(cd, struct video_device,
> class_dev) static inline int __must_check
>  video_device_create_file(struct video_device *vfd,
>  			 struct class_device_attribute *attr)

Best regards
Luca Risolia

Re: [PATCH] v4l: fix build error for et61x251 driver

[aherrman]

On Fri, Sep 14, 2007 at 03:53:06AM +0200, Luca Risolia wrote:
> On Friday 14 September 2007 02:09:01 Linus Torvalds wrote:
> > On Fri, 14 Sep 2007, Luca Risolia wrote:
> > > Hacked-by: Luca Risolia <luca.risolia@studio.unibo.it>
> > >
> > > On Friday 14 September 2007 00:27:17 Andreas Herrmann wrote:
> > > > This fixes a kernel build problem and
> > > > should make it into 2.6.23, I think.
> > > >
> > > >



> > This patch is really ugly.

Well, yes. I should have known as I converted so many occurences of
to_video_device to container_of in my second patch.

> > Why can't the "to_video_device()" macro be used? Just move it to a place
> > where it's usable! IOW, what's wrong with the *much* simpler patch below?
> 
> There's nothing wtong in my opinion. I do not know the exact reason why Mauro 
> moved "to_video_device()" into CONFIG_VIDEO_V4L1_COMPAT. Pheraps he can give 
> more details about this change.

BTW, just a few V4L2 drivers and videodev seem to use this construct:
  video/usbvision/usbvision-video.c:    container_of(cd, struct video_device, class_dev);

  video/sn9c102/sn9c102_core.c:   cam = video_get_drvdata(container_of(cd, struct video_device,
  video/sn9c102/sn9c102_core.c-                                        class_dev));

  video/videodev.c:       struct video_device *vfd = container_of(cd, struct video_device,
  video/videodev.c-                                               class_dev);

And then their are drivers with other variants of container_of, e.g.:
  video/pvrusb2/pvrusb2-v4l2.c:   vp = container_of(chp,struct pvr2_v4l2,channel);
  video/bt8xx/bttv-vbi.c: struct bttv_buffer *buf = container_of(vb,struct bttv_buffer,vb);
   ...

I think, there should be a to_video_device macro for usage in v4l2.
An most probable for the other container_of stuff (when more there is more
than one occurence of a particular construct), drivers should provide their own macro,
e.g. to_video_buffer() or so.

That's what other subsystems do. It is more self-explanatory than a direct usage
of container_of.

So why not apply (my first patch ... oh no, of course that's  rubbish ;-) 
Linus' below patch for 2.6.23 to fix the compilation for that particular driver.
And to work on the conversion of container_of() stuff to meaningful macros for the
next kernel release?


Regards,

Andreas


> 
> 
> > That "to_video_device()" macro has absolutely _nothing_ to do with
> > CONFIG_VIDEO_V4L1_COMPAT, as far as I can tell!
> >
> > 			Linus
> > ---
> > diff --git a/include/media/v4l2-dev.h b/include/media/v4l2-dev.h
> > index d62847f..17f8f3a 100644
> > --- a/include/media/v4l2-dev.h
> > +++ b/include/media/v4l2-dev.h
> > @@ -337,6 +337,9 @@ void *priv;
> >  	struct class_device class_dev; /* sysfs */
> >  };
> >
> > +/* Class-dev to video-device */
> > +#define to_video_device(cd) container_of(cd, struct video_device,
> > class_dev) +
> >  /* Version 2 functions */
> >  extern int video_register_device(struct video_device *vfd, int type, int
> > nr); void video_unregister_device(struct video_device *);
> > @@ -354,11 +357,9 @@ extern int video_usercopy(struct inode *inode, struct
> > file *file, int (*func)(struct inode *inode, struct file *file,
> >  				      unsigned int cmd, void *arg));
> >
> > -
> >  #ifdef CONFIG_VIDEO_V4L1_COMPAT
> >  #include <linux/mm.h>
> >
> > -#define to_video_device(cd) container_of(cd, struct video_device,
> > class_dev) static inline int __must_check
> >  video_device_create_file(struct video_device *vfd,
> >  			 struct class_device_attribute *attr)
> 
> Best regards
> Luca Risolia

Re: [PATCH] v4l: fix build error for et61x251 driver

[Mauro Carvalho Chehab]

> > > This patch is really ugly.
> 
> Well, yes. I should have known as I converted so many occurences of
> to_video_device to container_of in my second patch.
> 
> > > Why can't the "to_video_device()" macro be used? Just move it to a place
> > > where it's usable! IOW, what's wrong with the *much* simpler patch below?
> > 
> > There's nothing wtong in my opinion. I do not know the exact reason why Mauro 
> > moved "to_video_device()" into CONFIG_VIDEO_V4L1_COMPAT. Pheraps he can give 
> > more details about this change.
> 
> BTW, just a few V4L2 drivers and videodev seem to use this construct:
>   video/usbvision/usbvision-video.c:    container_of(cd, struct video_device, class_dev);
> 
>   video/sn9c102/sn9c102_core.c:   cam = video_get_drvdata(container_of(cd, struct video_device,
>   video/sn9c102/sn9c102_core.c-                                        class_dev));
> 
>   video/videodev.c:       struct video_device *vfd = container_of(cd, struct video_device,
>   video/videodev.c-                                               class_dev);
> 
> And then their are drivers with other variants of container_of, e.g.:
>   video/pvrusb2/pvrusb2-v4l2.c:   vp = container_of(chp,struct pvr2_v4l2,channel);
>   video/bt8xx/bttv-vbi.c: struct bttv_buffer *buf = container_of(vb,struct bttv_buffer,vb);
>    ...
> 
> I think, there should be a to_video_device macro for usage in v4l2.
> An most probable for the other container_of stuff (when more there is more
> than one occurence of a particular construct), drivers should provide their own macro,
> e.g. to_video_buffer() or so.
> 
> That's what other subsystems do. It is more self-explanatory than a direct usage
> of container_of.
> 
> So why not apply (my first patch ... oh no, of course that's  rubbish ;-) 
> Linus' below patch for 2.6.23 to fix the compilation for that particular driver.
> And to work on the conversion of container_of() stuff to meaningful macros for the
> next kernel release?

The to_video_device and the container_of (cd, struct video_device,
class_dev) (as you noticed at the above drivers) are used to provide
procfs interface.

On videodev, there's the v4l2 core stuff, used on all V4L drivers. It
allows some control to the V4L devices (basically, see/change the
modprobe loading parameters).

The other drivers that uses to_video_device (or the container_of
alternative) to create other userspace interfaces, specific to each
driver and not documented at V4L2 API:

bttv-driver.c:static CLASS_DEVICE_ATTR(card, S_IRUGO, show_card, NULL);
et61x251_core.c:static CLASS_DEVICE_ATTR(reg, S_IRUGO | S_IWUSR,
et61x251_core.c:static CLASS_DEVICE_ATTR(val, S_IRUGO | S_IWUSR,
et61x251_core.c:static CLASS_DEVICE_ATTR(i2c_reg, S_IRUGO | S_IWUSR,
et61x251_core.c:static CLASS_DEVICE_ATTR(i2c_val, S_IRUGO | S_IWUSR,
ov511.c:static CLASS_DEVICE_ATTR(custom_id, S_IRUGO, show_custom_id, NULL);
ov511.c:static CLASS_DEVICE_ATTR(model, S_IRUGO, show_model, NULL);
ov511.c:static CLASS_DEVICE_ATTR(bridge, S_IRUGO, show_bridge, NULL);
ov511.c:static CLASS_DEVICE_ATTR(sensor, S_IRUGO, show_sensor, NULL);
ov511.c:static CLASS_DEVICE_ATTR(brightness, S_IRUGO, show_brightness, NULL);
ov511.c:static CLASS_DEVICE_ATTR(saturation, S_IRUGO, show_saturation, NULL);
ov511.c:static CLASS_DEVICE_ATTR(contrast, S_IRUGO, show_contrast, NULL);
ov511.c:static CLASS_DEVICE_ATTR(hue, S_IRUGO, show_hue, NULL);
ov511.c:static CLASS_DEVICE_ATTR(exposure, S_IRUGO, show_exposure, NULL);
pwc-if.c:static CLASS_DEVICE_ATTR(pan_tilt, S_IRUGO | S_IWUSR, show_pan_tilt,
pwc-if.c:static CLASS_DEVICE_ATTR(button, S_IRUGO | S_IWUSR, show_snapshot_button_status,
sn9c102_core.c:static CLASS_DEVICE_ATTR(reg, S_IRUGO | S_IWUSR,
sn9c102_core.c:static CLASS_DEVICE_ATTR(val, S_IRUGO | S_IWUSR,
sn9c102_core.c:static CLASS_DEVICE_ATTR(i2c_reg, S_IRUGO | S_IWUSR,
sn9c102_core.c:static CLASS_DEVICE_ATTR(i2c_val, S_IRUGO | S_IWUSR,
sn9c102_core.c:static CLASS_DEVICE_ATTR(green, S_IWUGO, NULL, sn9c102_store_green);
sn9c102_core.c:static CLASS_DEVICE_ATTR(blue, S_IWUGO, NULL, sn9c102_store_blue);
sn9c102_core.c:static CLASS_DEVICE_ATTR(red, S_IWUGO, NULL, sn9c102_store_red);
sn9c102_core.c:static CLASS_DEVICE_ATTR(frame_header, S_IRUGO,
stv680.c:static CLASS_DEVICE_ATTR(name, S_IRUGO, show_##name, NULL);
usbvision-video.c:static CLASS_DEVICE_ATTR(version, S_IRUGO, show_version, NULL);
usbvision-video.c:static CLASS_DEVICE_ATTR(model, S_IRUGO, show_model, NULL);
usbvision-video.c:static CLASS_DEVICE_ATTR(hue, S_IRUGO, show_hue, NULL);
usbvision-video.c:static CLASS_DEVICE_ATTR(contrast, S_IRUGO, show_contrast, NULL);
usbvision-video.c:static CLASS_DEVICE_ATTR(brightness, S_IRUGO, show_brightness, NULL);
usbvision-video.c:static CLASS_DEVICE_ATTR(saturation, S_IRUGO, show_saturation, NULL);
usbvision-video.c:static CLASS_DEVICE_ATTR(streaming, S_IRUGO, show_streaming, NULL);
usbvision-video.c:static CLASS_DEVICE_ATTR(compression, S_IRUGO, show_compression, NULL);
usbvision-video.c:static CLASS_DEVICE_ATTR(bridge, S_IRUGO, show_device_bridge, NULL);

>From the above, you can clearly see that et62x251 and s9c102 provides an
interface to directly change a register at the device. The other drivers
allows reading/changing a few controls directly via /proc (this is also
possible, using V4L2 interface). This is not recommended, since V4L2 API
should be the proper way to control the devices.

>From my POV, a driver that is creating its own userspace API is not
fully compliant with V4L2 API.

So, the proper fix is to make those drivers dependent of V4L1, where
this kind of usage were valid.

Cheers,
Mauro

Re: [PATCH] v4l: fix build error for et61x251 driver

[Luca Risolia]

On Friday 14 September 2007 14:50:11 Mauro Carvalho Chehab wrote:
> > > > This patch is really ugly.
> >
> > Well, yes. I should have known as I converted so many occurences of
> > to_video_device to container_of in my second patch.
> >
> > > > Why can't the "to_video_device()" macro be used? Just move it to a
> > > > place where it's usable! IOW, what's wrong with the *much* simpler
> > > > patch below?
> > >
> > > There's nothing wtong in my opinion. I do not know the exact reason why
> > > Mauro moved "to_video_device()" into CONFIG_VIDEO_V4L1_COMPAT. Pheraps
> > > he can give more details about this change.
> >
> > BTW, just a few V4L2 drivers and videodev seem to use this construct:
> >   video/usbvision/usbvision-video.c:    container_of(cd, struct
> > video_device, class_dev);
> >
> >   video/sn9c102/sn9c102_core.c:   cam =
> > video_get_drvdata(container_of(cd, struct video_device,
> > video/sn9c102/sn9c102_core.c-                                       
> > class_dev));
> >
> >   video/videodev.c:       struct video_device *vfd = container_of(cd,
> > struct video_device, video/videodev.c-                                   
> >            class_dev);
> >
> > And then their are drivers with other variants of container_of, e.g.:
> >   video/pvrusb2/pvrusb2-v4l2.c:   vp = container_of(chp,struct
> > pvr2_v4l2,channel); video/bt8xx/bttv-vbi.c: struct bttv_buffer *buf =
> > container_of(vb,struct bttv_buffer,vb); ...
> >
> > I think, there should be a to_video_device macro for usage in v4l2.
> > An most probable for the other container_of stuff (when more there is
> > more than one occurence of a particular construct), drivers should
> > provide their own macro, e.g. to_video_buffer() or so.
> >
> > That's what other subsystems do. It is more self-explanatory than a
> > direct usage of container_of.
> >
> > So why not apply (my first patch ... oh no, of course that's  rubbish ;-)
> > Linus' below patch for 2.6.23 to fix the compilation for that particular
> > driver. And to work on the conversion of container_of() stuff to
> > meaningful macros for the next kernel release?
>
> The to_video_device and the container_of (cd, struct video_device,
> class_dev) (as you noticed at the above drivers) are used to provide
> procfs interface.
>
> On videodev, there's the v4l2 core stuff, used on all V4L drivers. It
> allows some control to the V4L devices (basically, see/change the
> modprobe loading parameters).
>
> The other drivers that uses to_video_device (or the container_of
> alternative) to create other userspace interfaces, specific to each
> driver and not documented at V4L2 API:
>
> bttv-driver.c:static CLASS_DEVICE_ATTR(card, S_IRUGO, show_card, NULL);
> et61x251_core.c:static CLASS_DEVICE_ATTR(reg, S_IRUGO | S_IWUSR,
> et61x251_core.c:static CLASS_DEVICE_ATTR(val, S_IRUGO | S_IWUSR,
> et61x251_core.c:static CLASS_DEVICE_ATTR(i2c_reg, S_IRUGO | S_IWUSR,
> et61x251_core.c:static CLASS_DEVICE_ATTR(i2c_val, S_IRUGO | S_IWUSR,
> ov511.c:static CLASS_DEVICE_ATTR(custom_id, S_IRUGO, show_custom_id, NULL);
> ov511.c:static CLASS_DEVICE_ATTR(model, S_IRUGO, show_model, NULL);
> ov511.c:static CLASS_DEVICE_ATTR(bridge, S_IRUGO, show_bridge, NULL);
> ov511.c:static CLASS_DEVICE_ATTR(sensor, S_IRUGO, show_sensor, NULL);
> ov511.c:static CLASS_DEVICE_ATTR(brightness, S_IRUGO, show_brightness,
> NULL); ov511.c:static CLASS_DEVICE_ATTR(saturation, S_IRUGO,
> show_saturation, NULL); ov511.c:static CLASS_DEVICE_ATTR(contrast, S_IRUGO,
> show_contrast, NULL); ov511.c:static CLASS_DEVICE_ATTR(hue, S_IRUGO,
> show_hue, NULL);
> ov511.c:static CLASS_DEVICE_ATTR(exposure, S_IRUGO, show_exposure, NULL);
> pwc-if.c:static CLASS_DEVICE_ATTR(pan_tilt, S_IRUGO | S_IWUSR,
> show_pan_tilt, pwc-if.c:static CLASS_DEVICE_ATTR(button, S_IRUGO | S_IWUSR,
> show_snapshot_button_status, sn9c102_core.c:static CLASS_DEVICE_ATTR(reg,
> S_IRUGO | S_IWUSR,
> sn9c102_core.c:static CLASS_DEVICE_ATTR(val, S_IRUGO | S_IWUSR,
> sn9c102_core.c:static CLASS_DEVICE_ATTR(i2c_reg, S_IRUGO | S_IWUSR,
> sn9c102_core.c:static CLASS_DEVICE_ATTR(i2c_val, S_IRUGO | S_IWUSR,
> sn9c102_core.c:static CLASS_DEVICE_ATTR(green, S_IWUGO, NULL,
> sn9c102_store_green); sn9c102_core.c:static CLASS_DEVICE_ATTR(blue,
> S_IWUGO, NULL, sn9c102_store_blue); sn9c102_core.c:static
> CLASS_DEVICE_ATTR(red, S_IWUGO, NULL, sn9c102_store_red);
> sn9c102_core.c:static CLASS_DEVICE_ATTR(frame_header, S_IRUGO,
> stv680.c:static CLASS_DEVICE_ATTR(name, S_IRUGO, show_##name, NULL);
> usbvision-video.c:static CLASS_DEVICE_ATTR(version, S_IRUGO, show_version,
> NULL); usbvision-video.c:static CLASS_DEVICE_ATTR(model, S_IRUGO,
> show_model, NULL); usbvision-video.c:static CLASS_DEVICE_ATTR(hue, S_IRUGO,
> show_hue, NULL); usbvision-video.c:static CLASS_DEVICE_ATTR(contrast,
> S_IRUGO, show_contrast, NULL); usbvision-video.c:static
> CLASS_DEVICE_ATTR(brightness, S_IRUGO, show_brightness, NULL);
> usbvision-video.c:static CLASS_DEVICE_ATTR(saturation, S_IRUGO,
> show_saturation, NULL); usbvision-video.c:static
> CLASS_DEVICE_ATTR(streaming, S_IRUGO, show_streaming, NULL);
> usbvision-video.c:static CLASS_DEVICE_ATTR(compression, S_IRUGO,
> show_compression, NULL); usbvision-video.c:static CLASS_DEVICE_ATTR(bridge,
> S_IRUGO, show_device_bridge, NULL);
>
> From the above, you can clearly see that et62x251 and s9c102 provides an
> interface to directly change a register at the device. The other drivers
> allows reading/changing a few controls directly via /proc (this is also
> possible, using V4L2 interface). This is not recommended, since V4L2 API
> should be the proper way to control the devices.


through ioctl()? It's not as immediate and safe as controlling the device 
registers through /sysfs (not /proc). However, the sysfs interface in those 
drivers appeared before V4L2 had its own ioctls and we agreed to keep and 
export the interface to the only users selecting CONFIG_VIDEO_ADV_DEBUG (ok, 
this is actually valid for the sn9c102, I'll submit a patch for the et61x251 
in the future). 


> From my POV, a driver that is creating its own userspace API is not
> fully compliant with V4L2 API.

Isn't Video4Linux2 ioctl() supersedeing sysfs in this case?


> Cheers,
> Mauro

Best regards
Luca Risolia

Re: [PATCH] v4l: fix build error for et61x251 driver

[Mauro Carvalho Chehab]

> through ioctl()? It's not as immediate and safe as controlling the device
> registers through /sysfs (not /proc). However, the sysfs interface in those
> drivers appeared before V4L2 had its own ioctls and we agreed to keep and
> export the interface to the only users selecting CONFIG_VIDEO_ADV_DEBUG (ok,
> this is actually valid for the sn9c102, I'll submit a patch for the et61x251
> in the future).

Direct register access for debug ok, but not this is not ok for 
normal usage.
>
>
>> From my POV, a driver that is creating its own userspace API is not
>> fully compliant with V4L2 API.
>
> Isn't Video4Linux2 ioctl() supersedeing sysfs in this case?

It should be. However, things like direct register access (for non-debug 
mode) may allow some controls that weren't visible via ioctl. That's why 
the sysfs usage may be evil: a driver may have some parts accessible only 
via sysfs interface, on a non-standard way, without offering the official 
API support. So, some device functionalities may be hidden from userspace 
apps that are compliant with V4L2.

Summarizing:

Linus patch seems to be the better solution to solve the V4L1_COMPAT bug.

I would also convert the other container_of stuff to to_video_device (to 
have code uniformity).

et61x251 direct register interfaces should be available only if 
CONFIG_VIDEO_ADV_DEBUG is selected to avoid its miss-usage. If there are 
other device configurations that needs specific register settings not yet 
provided, this should be provided via V4L2 standard ioctls.

This way, et61x251 will be compliant with V4L2.

I still think that we should work at the remaining sysfs classes to make 
them coherent on all V4L devices.

Cheers,
Mauro.