diff mbox series

[1/2] media: dvbdev: make dvb_class constant

Message ID 20240305-class_cleanup-media-v1-1-53e1538973cd@marliere.net (mailing list archive)
State New, archived
Headers show
Series media: constify struct class usage | expand

Commit Message

Ricardo B. Marliere March 5, 2024, 1:26 p.m. UTC 
Since commit 43a7206b0963 ("driver core: class: make class_register() take
a const *"), the driver core allows for struct class to be in read-only
memory, so move the dvb_class structure to be declared at build time
placing it into read-only memory, instead of having to be dynamically
allocated at boot time.

Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Suggested-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ricardo B. Marliere <ricardo@marliere.net>
---
 drivers/media/dvb-core/dvbdev.c | 23 +++++++++++++----------
 1 file changed, 13 insertions(+), 10 deletions(-)

Comments

Hans Verkuil April 8, 2024, 9:47 a.m. UTC | #1 
On 05/03/2024 14:26, Ricardo B. Marliere wrote:
> Since commit 43a7206b0963 ("driver core: class: make class_register() take
> a const *"), the driver core allows for struct class to be in read-only
> memory, so move the dvb_class structure to be declared at build time
> placing it into read-only memory, instead of having to be dynamically
> allocated at boot time.
> 
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Suggested-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Signed-off-by: Ricardo B. Marliere <ricardo@marliere.net>
> ---
>  drivers/media/dvb-core/dvbdev.c | 23 +++++++++++++----------
>  1 file changed, 13 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/media/dvb-core/dvbdev.c b/drivers/media/dvb-core/dvbdev.c
> index 733d0bc4b4cc..dcbf68b00240 100644
> --- a/drivers/media/dvb-core/dvbdev.c
> +++ b/drivers/media/dvb-core/dvbdev.c
> @@ -78,7 +78,13 @@ static const u8 minor_type[] = {
>  #define MAX_DVB_MINORS		(DVB_MAX_ADAPTERS * 64)
>  #endif
>  
> -static struct class *dvb_class;
> +static int dvb_uevent(const struct device *dev, struct kobj_uevent_env *env);
> +static char *dvb_devnode(const struct device *dev, umode_t *mode);

Forward references are typically something you want to avoid.

Looking at the code, I think it makes sense to just move those two functions
to just before this dvb_class.

> +static const struct class dvb_class = {
> +	.name = "dvb",
> +	.dev_uevent = dvb_uevent,
> +	.devnode = dvb_devnode,
> +};
>  
>  static struct dvb_device *dvb_minors[MAX_DVB_MINORS];
>  static DECLARE_RWSEM(minor_rwsem);

Also move the dvb_class (+ the two functions) to after this line. I think that's
a more suitable place for this.

> @@ -561,7 +567,7 @@ int dvb_register_device(struct dvb_adapter *adap, struct dvb_device **pdvbdev,
>  		return ret;
>  	}
>  
> -	clsdev = device_create(dvb_class, adap->device,
> +	clsdev = device_create(&dvb_class, adap->device,
>  			       MKDEV(DVB_MAJOR, minor),
>  			       dvbdev, "dvb%d.%s%d", adap->num, dnames[type], id);
>  	if (IS_ERR(clsdev)) {
> @@ -600,7 +606,7 @@ void dvb_remove_device(struct dvb_device *dvbdev)
>  
>  	dvb_media_device_free(dvbdev);
>  
> -	device_destroy(dvb_class, MKDEV(DVB_MAJOR, dvbdev->minor));
> +	device_destroy(&dvb_class, MKDEV(DVB_MAJOR, dvbdev->minor));
>  
>  	list_del(&dvbdev->list_head);
>  }
> @@ -1096,13 +1102,10 @@ static int __init init_dvbdev(void)
>  		goto error;
>  	}
>  
> -	dvb_class = class_create("dvb");
> -	if (IS_ERR(dvb_class)) {
> -		retval = PTR_ERR(dvb_class);
> +	retval = class_register(&dvb_class);
> +	if (retval != 0)

This can just be 'if (retval)'.

>  		goto error;
> -	}
> -	dvb_class->dev_uevent = dvb_uevent;
> -	dvb_class->devnode = dvb_devnode;
> +
>  	return 0;
>  
>  error:
> @@ -1115,7 +1118,7 @@ static void __exit exit_dvbdev(void)
>  {
>  	struct dvbdevfops_node *node, *next;
>  
> -	class_destroy(dvb_class);
> +	class_unregister(&dvb_class);
>  	cdev_del(&dvb_device_cdev);
>  	unregister_chrdev_region(MKDEV(DVB_MAJOR, 0), MAX_DVB_MINORS);
>  
> 

Regards,

	Hans
Ricardo B. Marliere April 8, 2024, 10:47 a.m. UTC | #2 
Hi Hans!

On  8 Apr 11:47, Hans Verkuil wrote:
> On 05/03/2024 14:26, Ricardo B. Marliere wrote:
> > Since commit 43a7206b0963 ("driver core: class: make class_register() take
> > a const *"), the driver core allows for struct class to be in read-only
> > memory, so move the dvb_class structure to be declared at build time
> > placing it into read-only memory, instead of having to be dynamically
> > allocated at boot time.
> > 
> > Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> > Suggested-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> > Signed-off-by: Ricardo B. Marliere <ricardo@marliere.net>
> > ---
> >  drivers/media/dvb-core/dvbdev.c | 23 +++++++++++++----------
> >  1 file changed, 13 insertions(+), 10 deletions(-)
> > 
> > diff --git a/drivers/media/dvb-core/dvbdev.c b/drivers/media/dvb-core/dvbdev.c
> > index 733d0bc4b4cc..dcbf68b00240 100644
> > --- a/drivers/media/dvb-core/dvbdev.c
> > +++ b/drivers/media/dvb-core/dvbdev.c
> > @@ -78,7 +78,13 @@ static const u8 minor_type[] = {
> >  #define MAX_DVB_MINORS		(DVB_MAX_ADAPTERS * 64)
> >  #endif
> >  
> > -static struct class *dvb_class;
> > +static int dvb_uevent(const struct device *dev, struct kobj_uevent_env *env);
> > +static char *dvb_devnode(const struct device *dev, umode_t *mode);
> 
> Forward references are typically something you want to avoid.
> 
> Looking at the code, I think it makes sense to just move those two functions
> to just before this dvb_class.

Ack.

> 
> > +static const struct class dvb_class = {
> > +	.name = "dvb",
> > +	.dev_uevent = dvb_uevent,
> > +	.devnode = dvb_devnode,
> > +};
> >  
> >  static struct dvb_device *dvb_minors[MAX_DVB_MINORS];
> >  static DECLARE_RWSEM(minor_rwsem);
> 
> Also move the dvb_class (+ the two functions) to after this line. I think that's
> a more suitable place for this.

Ack.

> 
> > @@ -561,7 +567,7 @@ int dvb_register_device(struct dvb_adapter *adap, struct dvb_device **pdvbdev,
> >  		return ret;
> >  	}
> >  
> > -	clsdev = device_create(dvb_class, adap->device,
> > +	clsdev = device_create(&dvb_class, adap->device,
> >  			       MKDEV(DVB_MAJOR, minor),
> >  			       dvbdev, "dvb%d.%s%d", adap->num, dnames[type], id);
> >  	if (IS_ERR(clsdev)) {
> > @@ -600,7 +606,7 @@ void dvb_remove_device(struct dvb_device *dvbdev)
> >  
> >  	dvb_media_device_free(dvbdev);
> >  
> > -	device_destroy(dvb_class, MKDEV(DVB_MAJOR, dvbdev->minor));
> > +	device_destroy(&dvb_class, MKDEV(DVB_MAJOR, dvbdev->minor));
> >  
> >  	list_del(&dvbdev->list_head);
> >  }
> > @@ -1096,13 +1102,10 @@ static int __init init_dvbdev(void)
> >  		goto error;
> >  	}
> >  
> > -	dvb_class = class_create("dvb");
> > -	if (IS_ERR(dvb_class)) {
> > -		retval = PTR_ERR(dvb_class);
> > +	retval = class_register(&dvb_class);
> > +	if (retval != 0)
> 
> This can just be 'if (retval)'.

But then it would be on a different style than the rest of the function:

static int __init init_dvbdev(void)
{
	int retval;
	dev_t dev = MKDEV(DVB_MAJOR, 0);

	retval = register_chrdev_region(dev, MAX_DVB_MINORS, "DVB");
	if (retval != 0) {
		pr_err("dvb-core: unable to get major %d\n", DVB_MAJOR);
		return retval;
	}

	cdev_init(&dvb_device_cdev, &dvb_device_fops);
	retval = cdev_add(&dvb_device_cdev, dev, MAX_DVB_MINORS);
	if (retval != 0) {
		pr_err("dvb-core: unable register character device\n");
		goto error;
	}

	retval = class_register(&dvb_class);
	if (retval != 0)
		goto error;

	return 0;

error:
	cdev_del(&dvb_device_cdev);
	unregister_chrdev_region(dev, MAX_DVB_MINORS);
	return retval;
}


> 
> >  		goto error;
> > -	}
> > -	dvb_class->dev_uevent = dvb_uevent;
> > -	dvb_class->devnode = dvb_devnode;
> > +
> >  	return 0;
> >  
> >  error:
> > @@ -1115,7 +1118,7 @@ static void __exit exit_dvbdev(void)
> >  {
> >  	struct dvbdevfops_node *node, *next;
> >  
> > -	class_destroy(dvb_class);
> > +	class_unregister(&dvb_class);
> >  	cdev_del(&dvb_device_cdev);
> >  	unregister_chrdev_region(MKDEV(DVB_MAJOR, 0), MAX_DVB_MINORS);
> >  
> > 
> 
> Regards,
> 
> 	Hans
Hans Verkuil April 8, 2024, 11:23 a.m. UTC | #3 
On 08/04/2024 12:47, Ricardo B. Marliere wrote:
> Hi Hans!
> 
> On  8 Apr 11:47, Hans Verkuil wrote:
>> On 05/03/2024 14:26, Ricardo B. Marliere wrote:
>>> Since commit 43a7206b0963 ("driver core: class: make class_register() take
>>> a const *"), the driver core allows for struct class to be in read-only
>>> memory, so move the dvb_class structure to be declared at build time
>>> placing it into read-only memory, instead of having to be dynamically
>>> allocated at boot time.
>>>
>>> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
>>> Suggested-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
>>> Signed-off-by: Ricardo B. Marliere <ricardo@marliere.net>
>>> ---
>>>  drivers/media/dvb-core/dvbdev.c | 23 +++++++++++++----------
>>>  1 file changed, 13 insertions(+), 10 deletions(-)
>>>
>>> diff --git a/drivers/media/dvb-core/dvbdev.c b/drivers/media/dvb-core/dvbdev.c
>>> index 733d0bc4b4cc..dcbf68b00240 100644
>>> --- a/drivers/media/dvb-core/dvbdev.c
>>> +++ b/drivers/media/dvb-core/dvbdev.c
>>> @@ -78,7 +78,13 @@ static const u8 minor_type[] = {
>>>  #define MAX_DVB_MINORS		(DVB_MAX_ADAPTERS * 64)
>>>  #endif
>>>  
>>> -static struct class *dvb_class;
>>> +static int dvb_uevent(const struct device *dev, struct kobj_uevent_env *env);
>>> +static char *dvb_devnode(const struct device *dev, umode_t *mode);
>>
>> Forward references are typically something you want to avoid.
>>
>> Looking at the code, I think it makes sense to just move those two functions
>> to just before this dvb_class.
> 
> Ack.
> 
>>
>>> +static const struct class dvb_class = {
>>> +	.name = "dvb",
>>> +	.dev_uevent = dvb_uevent,
>>> +	.devnode = dvb_devnode,
>>> +};
>>>  
>>>  static struct dvb_device *dvb_minors[MAX_DVB_MINORS];
>>>  static DECLARE_RWSEM(minor_rwsem);
>>
>> Also move the dvb_class (+ the two functions) to after this line. I think that's
>> a more suitable place for this.
> 
> Ack.
> 
>>
>>> @@ -561,7 +567,7 @@ int dvb_register_device(struct dvb_adapter *adap, struct dvb_device **pdvbdev,
>>>  		return ret;
>>>  	}
>>>  
>>> -	clsdev = device_create(dvb_class, adap->device,
>>> +	clsdev = device_create(&dvb_class, adap->device,
>>>  			       MKDEV(DVB_MAJOR, minor),
>>>  			       dvbdev, "dvb%d.%s%d", adap->num, dnames[type], id);
>>>  	if (IS_ERR(clsdev)) {
>>> @@ -600,7 +606,7 @@ void dvb_remove_device(struct dvb_device *dvbdev)
>>>  
>>>  	dvb_media_device_free(dvbdev);
>>>  
>>> -	device_destroy(dvb_class, MKDEV(DVB_MAJOR, dvbdev->minor));
>>> +	device_destroy(&dvb_class, MKDEV(DVB_MAJOR, dvbdev->minor));
>>>  
>>>  	list_del(&dvbdev->list_head);
>>>  }
>>> @@ -1096,13 +1102,10 @@ static int __init init_dvbdev(void)
>>>  		goto error;
>>>  	}
>>>  
>>> -	dvb_class = class_create("dvb");
>>> -	if (IS_ERR(dvb_class)) {
>>> -		retval = PTR_ERR(dvb_class);
>>> +	retval = class_register(&dvb_class);
>>> +	if (retval != 0)
>>
>> This can just be 'if (retval)'.
> 
> But then it would be on a different style than the rest of the function:

Ah, I hadn't noticed that. Let's keep it as you proposed then.

Regards,

	Hans

> 
> static int __init init_dvbdev(void)
> {
> 	int retval;
> 	dev_t dev = MKDEV(DVB_MAJOR, 0);
> 
> 	retval = register_chrdev_region(dev, MAX_DVB_MINORS, "DVB");
> 	if (retval != 0) {
> 		pr_err("dvb-core: unable to get major %d\n", DVB_MAJOR);
> 		return retval;
> 	}
> 
> 	cdev_init(&dvb_device_cdev, &dvb_device_fops);
> 	retval = cdev_add(&dvb_device_cdev, dev, MAX_DVB_MINORS);
> 	if (retval != 0) {
> 		pr_err("dvb-core: unable register character device\n");
> 		goto error;
> 	}
> 
> 	retval = class_register(&dvb_class);
> 	if (retval != 0)
> 		goto error;
> 
> 	return 0;
> 
> error:
> 	cdev_del(&dvb_device_cdev);
> 	unregister_chrdev_region(dev, MAX_DVB_MINORS);
> 	return retval;
> }
> 
> 
>>
>>>  		goto error;
>>> -	}
>>> -	dvb_class->dev_uevent = dvb_uevent;
>>> -	dvb_class->devnode = dvb_devnode;
>>> +
>>>  	return 0;
>>>  
>>>  error:
>>> @@ -1115,7 +1118,7 @@ static void __exit exit_dvbdev(void)
>>>  {
>>>  	struct dvbdevfops_node *node, *next;
>>>  
>>> -	class_destroy(dvb_class);
>>> +	class_unregister(&dvb_class);
>>>  	cdev_del(&dvb_device_cdev);
>>>  	unregister_chrdev_region(MKDEV(DVB_MAJOR, 0), MAX_DVB_MINORS);
>>>  
>>>
>>
>> Regards,
>>
>> 	Hans
diff mbox series

Patch

diff --git a/drivers/media/dvb-core/dvbdev.c b/drivers/media/dvb-core/dvbdev.c
index 733d0bc4b4cc..dcbf68b00240 100644
--- a/drivers/media/dvb-core/dvbdev.c
+++ b/drivers/media/dvb-core/dvbdev.c
@@ -78,7 +78,13 @@  static const u8 minor_type[] = {
 #define MAX_DVB_MINORS		(DVB_MAX_ADAPTERS * 64)
 #endif
 
-static struct class *dvb_class;
+static int dvb_uevent(const struct device *dev, struct kobj_uevent_env *env);
+static char *dvb_devnode(const struct device *dev, umode_t *mode);
+static const struct class dvb_class = {
+	.name = "dvb",
+	.dev_uevent = dvb_uevent,
+	.devnode = dvb_devnode,
+};
 
 static struct dvb_device *dvb_minors[MAX_DVB_MINORS];
 static DECLARE_RWSEM(minor_rwsem);
@@ -561,7 +567,7 @@  int dvb_register_device(struct dvb_adapter *adap, struct dvb_device **pdvbdev,
 		return ret;
 	}
 
-	clsdev = device_create(dvb_class, adap->device,
+	clsdev = device_create(&dvb_class, adap->device,
 			       MKDEV(DVB_MAJOR, minor),
 			       dvbdev, "dvb%d.%s%d", adap->num, dnames[type], id);
 	if (IS_ERR(clsdev)) {
@@ -600,7 +606,7 @@  void dvb_remove_device(struct dvb_device *dvbdev)
 
 	dvb_media_device_free(dvbdev);
 
-	device_destroy(dvb_class, MKDEV(DVB_MAJOR, dvbdev->minor));
+	device_destroy(&dvb_class, MKDEV(DVB_MAJOR, dvbdev->minor));
 
 	list_del(&dvbdev->list_head);
 }
@@ -1096,13 +1102,10 @@  static int __init init_dvbdev(void)
 		goto error;
 	}
 
-	dvb_class = class_create("dvb");
-	if (IS_ERR(dvb_class)) {
-		retval = PTR_ERR(dvb_class);
+	retval = class_register(&dvb_class);
+	if (retval != 0)
 		goto error;
-	}
-	dvb_class->dev_uevent = dvb_uevent;
-	dvb_class->devnode = dvb_devnode;
+
 	return 0;
 
 error:
@@ -1115,7 +1118,7 @@  static void __exit exit_dvbdev(void)
 {
 	struct dvbdevfops_node *node, *next;
 
-	class_destroy(dvb_class);
+	class_unregister(&dvb_class);
 	cdev_del(&dvb_device_cdev);
 	unregister_chrdev_region(MKDEV(DVB_MAJOR, 0), MAX_DVB_MINORS);