[PATCH] virt: coco: change tsm_class to a const struct

[PATCH] virt: coco: change tsm_class to a const struct

[Jori Koolstra]

The class_create() call has been deprecated in favor of class_register()
as the driver core now allows for a struct class to be in read-only
memory. Change tsm_class to be a const struct class and drop the
class_create() call. Compile tested only.

Link: https://lore.kernel.org/all/2023040244-duffel-pushpin-f738@gregkh/

Suggested-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Jori Koolstra <jkoolstra@xs4all.nl>
---
 drivers/virt/coco/tsm-core.c | 20 +++++++++++---------
 1 file changed, 11 insertions(+), 9 deletions(-)

diff --git a/drivers/virt/coco/tsm-core.c b/drivers/virt/coco/tsm-core.c
index 98dcf7d836df..04e347ea4b7c 100644
--- a/drivers/virt/coco/tsm-core.c
+++ b/drivers/virt/coco/tsm-core.c
@@ -9,7 +9,11 @@
 #include <linux/cleanup.h>
 #include <linux/pci-tsm.h>
 
-static struct class *tsm_class;
+static void tsm_release(struct device *);
+static const struct class tsm_class = {
+	.name		= "tsm",
+	.dev_release	= tsm_release
+};
 static DEFINE_IDA(tsm_ida);
 
 static int match_id(struct device *dev, const void *data)
@@ -22,7 +26,7 @@ static int match_id(struct device *dev, const void *data)
 
 struct tsm_dev *find_tsm_dev(int id)
 {
-	struct device *dev = class_find_device(tsm_class, NULL, &id, match_id);
+	struct device *dev = class_find_device(&tsm_class, NULL, &id, match_id);
 
 	if (!dev)
 		return NULL;
@@ -46,7 +50,7 @@ static struct tsm_dev *alloc_tsm_dev(struct device *parent)
 	tsm_dev->id = id;
 	dev = &tsm_dev->dev;
 	dev->parent = parent;
-	dev->class = tsm_class;
+	dev->class = &tsm_class;
 	device_initialize(dev);
 
 	return no_free_ptr(tsm_dev);
@@ -114,18 +118,16 @@ static void tsm_release(struct device *dev)
 
 static int __init tsm_init(void)
 {
-	tsm_class = class_create("tsm");
-	if (IS_ERR(tsm_class))
-		return PTR_ERR(tsm_class);
+	int err;
 
-	tsm_class->dev_release = tsm_release;
-	return 0;
+	err = class_register(&tsm_class);
+	return err;
 }
 module_init(tsm_init)
 
 static void __exit tsm_exit(void)
 {
-	class_destroy(tsm_class);
+	class_unregister(&tsm_class);
 }
 module_exit(tsm_exit)
 

base-commit: d466c332e106fe666d1e2f5a24d08e308bebbfa1
-- 
2.53.0

Re: [PATCH] virt: coco: change tsm_class to a const struct

[Thomas Weißschuh]

On Tue, Mar 03, 2026 at 08:05:55PM +0100, Jori Koolstra wrote:
> The class_create() call has been deprecated in favor of class_register()
> as the driver core now allows for a struct class to be in read-only
> memory. Change tsm_class to be a const struct class and drop the
> class_create() call. Compile tested only.
> 
> Link: https://lore.kernel.org/all/2023040244-duffel-pushpin-f738@gregkh/
> 
> Suggested-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Signed-off-by: Jori Koolstra <jkoolstra@xs4all.nl>

A small nitpick below, but in any case:

Reviewed-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>

(...)

> @@ -114,18 +118,16 @@ static void tsm_release(struct device *dev)
>  
>  static int __init tsm_init(void)
>  {
> -	tsm_class = class_create("tsm");
> -	if (IS_ERR(tsm_class))
> -		return PTR_ERR(tsm_class);
> +	int err;
>  
> -	tsm_class->dev_release = tsm_release;
> -	return 0;
> +	err = class_register(&tsm_class);
> +	return err;

'err' looks to be unnecessary now.

>  }

(...)

Re: [PATCH] virt: coco: change tsm_class to a const struct

[Jori Koolstra]

Hi Thomas,

> Op 04-03-2026 08:12 CET schreef Thomas Weißschuh <thomas.weissschuh@linutronix.de>:
> 
> > @@ -114,18 +118,16 @@ static void tsm_release(struct device *dev)
> >  
> >  static int __init tsm_init(void)
> >  {
> > -	tsm_class = class_create("tsm");
> > -	if (IS_ERR(tsm_class))
> > -		return PTR_ERR(tsm_class);
> > +	int err;
> >  
> > -	tsm_class->dev_release = tsm_release;
> > -	return 0;
> > +	err = class_register(&tsm_class);
> > +	return err;
> 
> 'err' looks to be unnecessary now.
> 
> >  }

This was what I had before. I thought that returning class_register() immediately,
even though it saves two lines, might be less readable. You either have to click
through to class_register() or know that these init functions return an error.
Is there convention for this?

thanks,
Jori.

Re: [PATCH] virt: coco: change tsm_class to a const struct

[Greg Kroah-Hartman]

On Wed, Mar 04, 2026 at 10:35:03AM +0100, Jori Koolstra wrote:
> Hi Thomas,
> 
> > Op 04-03-2026 08:12 CET schreef Thomas Weißschuh <thomas.weissschuh@linutronix.de>:
> > 
> > > @@ -114,18 +118,16 @@ static void tsm_release(struct device *dev)
> > >  
> > >  static int __init tsm_init(void)
> > >  {
> > > -	tsm_class = class_create("tsm");
> > > -	if (IS_ERR(tsm_class))
> > > -		return PTR_ERR(tsm_class);
> > > +	int err;
> > >  
> > > -	tsm_class->dev_release = tsm_release;
> > > -	return 0;
> > > +	err = class_register(&tsm_class);
> > > +	return err;
> > 
> > 'err' looks to be unnecessary now.
> > 
> > >  }
> 
> This was what I had before. I thought that returning class_register() immediately,
> even though it saves two lines, might be less readable. You either have to click
> through to class_register() or know that these init functions return an error.
> Is there convention for this?

A single line function of:

static int __init tsm_init(void)
{
	return class_register(&tsm_class);
}

Is just fine.

thanks,

greg k-h

Re: [PATCH] virt: coco: change tsm_class to a const struct

[Jori Koolstra]

> Op 04-03-2026 08:12 CET schreef Thomas Weißschuh <thomas.weissschuh@linutronix.de>:
> 
>  
> On Tue, Mar 03, 2026 at 08:05:55PM +0100, Jori Koolstra wrote:
> > The class_create() call has been deprecated in favor of class_register()
> > as the driver core now allows for a struct class to be in read-only
> > memory. Change tsm_class to be a const struct class and drop the
> > class_create() call. Compile tested only.
> > 
> > Link: https://lore.kernel.org/all/2023040244-duffel-pushpin-f738@gregkh/
> > 
> > Suggested-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> > Signed-off-by: Jori Koolstra <jkoolstra@xs4all.nl>
> 
> A small nitpick below, but in any case:
> 
> Reviewed-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
> 
> (...)
> 
> > @@ -114,18 +118,16 @@ static void tsm_release(struct device *dev)
> >  
> >  static int __init tsm_init(void)
> >  {
> > -	tsm_class = class_create("tsm");
> > -	if (IS_ERR(tsm_class))
> > -		return PTR_ERR(tsm_class);
> > +	int err;
> >  
> > -	tsm_class->dev_release = tsm_release;
> > -	return 0;
> > +	err = class_register(&tsm_class);
> > +	return err;
> 
> 'err' looks to be unnecessary now.
> 
> >  }
> 
> (...)

Hi Thomas,

I sent a v2 a while ago; I am not sure how to check if it has been applied.
Just going over the remaining class_create() patches again.

Thanks,
Jori.