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

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Message-ID: <2023081112-wistful-coping-f775@gregkh>
Date:   Fri, 11 Aug 2023 21:40:11 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Ivan Orlov <ivan.orlov0322@...il.com>
Cc:     tomas.winkler@...el.com, arnd@...db.de,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mei: make mei_class a static const structure

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@...uxfoundation.org>
> Signed-off-by: Ivan Orlov <ivan.orlov0322@...il.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