[PATCH] mei: make mei_class a static const structure

[PATCH] mei: make mei_class a static const structure

[Ivan Orlov]

Now that the driver core allows for struct class to be in read-only
memory, move the mei_class structure to be declared at build time
placing it into read-only memory, instead of having to be dynamically
allocated at boot time.

Suggested-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ivan Orlov <ivan.orlov0322@gmail.com>
---
 drivers/misc/mei/main.c | 19 ++++++++++---------
 1 file changed, 10 insertions(+), 9 deletions(-)

diff --git a/drivers/misc/mei/main.c b/drivers/misc/mei/main.c
index 51876da3fd65..902789d3106b 100644
--- a/drivers/misc/mei/main.c
+++ b/drivers/misc/mei/main.c
@@ -27,7 +27,9 @@
 #include "mei_dev.h"
 #include "client.h"
 
-static struct class *mei_class;
+static const struct class mei_class = {
+	.name = "mei",
+};
 static dev_t mei_devt;
 #define MEI_MAX_DEVS  MINORMASK
 static DEFINE_MUTEX(mei_minor_lock);
@@ -1115,7 +1117,7 @@ void mei_set_devstate(struct mei_device *dev, enum mei_dev_state state)
 
 	dev->dev_state = state;
 
-	clsdev = class_find_device_by_devt(mei_class, dev->cdev.dev);
+	clsdev = class_find_device_by_devt(&mei_class, dev->cdev.dev);
 	if (clsdev) {
 		sysfs_notify(&clsdev->kobj, NULL, "dev_state");
 		put_device(clsdev);
@@ -1232,7 +1234,7 @@ int mei_register(struct mei_device *dev, struct device *parent)
 		goto err_dev_add;
 	}
 
-	clsdev = device_create_with_groups(mei_class, parent, devno,
+	clsdev = device_create_with_groups(&mei_class, parent, devno,
 					   dev, mei_groups,
 					   "mei%d", dev->minor);
 
@@ -1264,7 +1266,7 @@ void mei_deregister(struct mei_device *dev)
 
 	mei_dbgfs_deregister(dev);
 
-	device_destroy(mei_class, devno);
+	device_destroy(&mei_class, devno);
 
 	mei_minor_free(dev);
 }
@@ -1274,10 +1276,9 @@ static int __init mei_init(void)
 {
 	int ret;
 
-	mei_class = class_create("mei");
-	if (IS_ERR(mei_class)) {
+	ret = class_register(&mei_class);
+	if (ret) {
 		pr_err("couldn't create class\n");
-		ret = PTR_ERR(mei_class);
 		goto err;
 	}
 
@@ -1298,7 +1299,7 @@ static int __init mei_init(void)
 err_chrdev:
 	unregister_chrdev_region(mei_devt, MEI_MAX_DEVS);
 err_class:
-	class_destroy(mei_class);
+	class_unregister(&mei_class);
 err:
 	return ret;
 }
@@ -1306,7 +1307,7 @@ static int __init mei_init(void)
 static void __exit mei_exit(void)
 {
 	unregister_chrdev_region(mei_devt, MEI_MAX_DEVS);
-	class_destroy(mei_class);
+	class_unregister(&mei_class);
 	mei_cl_bus_exit();
 }
 
-- 
2.34.1

Re: [PATCH] mei: make mei_class a static const structure

[Greg KH]

On Thu, Aug 10, 2023 at 11:46:52PM +0400, Ivan Orlov wrote:
> Now that the driver core allows for struct class to be in read-only
> memory, move the mei_class structure to be declared at build time
> placing it into read-only memory, instead of having to be dynamically
> allocated at boot time.
> 
> Suggested-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Signed-off-by: Ivan Orlov <ivan.orlov0322@gmail.com>
> ---
>  drivers/misc/mei/main.c | 19 ++++++++++---------
>  1 file changed, 10 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/misc/mei/main.c b/drivers/misc/mei/main.c
> index 51876da3fd65..902789d3106b 100644
> --- a/drivers/misc/mei/main.c
> +++ b/drivers/misc/mei/main.c
> @@ -27,7 +27,9 @@
>  #include "mei_dev.h"
>  #include "client.h"
>  
> -static struct class *mei_class;
> +static const struct class mei_class = {
> +	.name = "mei",
> +};
>  static dev_t mei_devt;

Extra line after the new structure?

>  #define MEI_MAX_DEVS  MINORMASK
>  static DEFINE_MUTEX(mei_minor_lock);
> @@ -1115,7 +1117,7 @@ void mei_set_devstate(struct mei_device *dev, enum mei_dev_state state)
>  
>  	dev->dev_state = state;
>  
> -	clsdev = class_find_device_by_devt(mei_class, dev->cdev.dev);
> +	clsdev = class_find_device_by_devt(&mei_class, dev->cdev.dev);
>  	if (clsdev) {
>  		sysfs_notify(&clsdev->kobj, NULL, "dev_state");
>  		put_device(clsdev);
> @@ -1232,7 +1234,7 @@ int mei_register(struct mei_device *dev, struct device *parent)
>  		goto err_dev_add;
>  	}
>  
> -	clsdev = device_create_with_groups(mei_class, parent, devno,
> +	clsdev = device_create_with_groups(&mei_class, parent, devno,
>  					   dev, mei_groups,
>  					   "mei%d", dev->minor);
>  
> @@ -1264,7 +1266,7 @@ void mei_deregister(struct mei_device *dev)
>  
>  	mei_dbgfs_deregister(dev);
>  
> -	device_destroy(mei_class, devno);
> +	device_destroy(&mei_class, devno);
>  
>  	mei_minor_free(dev);
>  }
> @@ -1274,10 +1276,9 @@ static int __init mei_init(void)
>  {
>  	int ret;
>  
> -	mei_class = class_create("mei");
> -	if (IS_ERR(mei_class)) {
> +	ret = class_register(&mei_class);
> +	if (ret) {
>  		pr_err("couldn't create class\n");

This message doesn't make sense anymore.  No need for it either, just
remove it and do a simple:
		return err;
here instead.

thanks,

greg k-h

Re: [PATCH] mei: make mei_class a static const structure

[Ivan Orlov]

On 8/11/23 23:40, Greg KH wrote:
> On Thu, Aug 10, 2023 at 11:46:52PM +0400, Ivan Orlov wrote:
>> Now that the driver core allows for struct class to be in read-only
>> memory, move the mei_class structure to be declared at build time
>> placing it into read-only memory, instead of having to be dynamically
>> allocated at boot time.
>>
>> Suggested-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
>> Signed-off-by: Ivan Orlov <ivan.orlov0322@gmail.com>
>> ---
>>   drivers/misc/mei/main.c | 19 ++++++++++---------
>>   1 file changed, 10 insertions(+), 9 deletions(-)
>>
>> diff --git a/drivers/misc/mei/main.c b/drivers/misc/mei/main.c
>> index 51876da3fd65..902789d3106b 100644
>> --- a/drivers/misc/mei/main.c
>> +++ b/drivers/misc/mei/main.c
>> @@ -27,7 +27,9 @@
>>   #include "mei_dev.h"
>>   #include "client.h"
>>   
>> -static struct class *mei_class;
>> +static const struct class mei_class = {
>> +	.name = "mei",
>> +};
>>   static dev_t mei_devt;
> 
> Extra line after the new structure?
> 
>>   #define MEI_MAX_DEVS  MINORMASK
>>   static DEFINE_MUTEX(mei_minor_lock);
>> @@ -1115,7 +1117,7 @@ void mei_set_devstate(struct mei_device *dev, enum mei_dev_state state)
>>   
>>   	dev->dev_state = state;
>>   
>> -	clsdev = class_find_device_by_devt(mei_class, dev->cdev.dev);
>> +	clsdev = class_find_device_by_devt(&mei_class, dev->cdev.dev);
>>   	if (clsdev) {
>>   		sysfs_notify(&clsdev->kobj, NULL, "dev_state");
>>   		put_device(clsdev);
>> @@ -1232,7 +1234,7 @@ int mei_register(struct mei_device *dev, struct device *parent)
>>   		goto err_dev_add;
>>   	}
>>   
>> -	clsdev = device_create_with_groups(mei_class, parent, devno,
>> +	clsdev = device_create_with_groups(&mei_class, parent, devno,
>>   					   dev, mei_groups,
>>   					   "mei%d", dev->minor);
>>   
>> @@ -1264,7 +1266,7 @@ void mei_deregister(struct mei_device *dev)
>>   
>>   	mei_dbgfs_deregister(dev);
>>   
>> -	device_destroy(mei_class, devno);
>> +	device_destroy(&mei_class, devno);
>>   
>>   	mei_minor_free(dev);
>>   }
>> @@ -1274,10 +1276,9 @@ static int __init mei_init(void)
>>   {
>>   	int ret;
>>   
>> -	mei_class = class_create("mei");
>> -	if (IS_ERR(mei_class)) {
>> +	ret = class_register(&mei_class);
>> +	if (ret) {
>>   		pr_err("couldn't create class\n");
> 
> This message doesn't make sense anymore.  No need for it either, just
> remove it and do a simple:
> 		return err;
> here instead.
> 
> thanks,
> 
> greg k-h


Hi Greg,

Thank you for the review, I'll make the suggested changes and send you 
the V2.

--
Kind regards,
Ivan Orlov