linux-kernel - Re: [PATCH] platform/x86: ISST: Simplify isst_misc_reg() and isst_misc

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Message-ID: <f6f3ca5a-8179-e678-aa8d-aeeacdcddb31@linux.intel.com>
Date: Mon, 12 Aug 2024 13:55:50 +0300 (EEST)
From: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
To: Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
cc: Hans de Goede <hdegoede@...hat.com>, 
    Andy Shevchenko <andriy.shevchenko@...ux.intel.com>, 
    platform-driver-x86@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] platform/x86: ISST: Simplify isst_misc_reg() and
 isst_misc_unreg()

On Wed, 31 Jul 2024, Srinivas Pandruvada wrote:

> After commit '1630dc626c87 ("platform/x86: ISST: Add model specific
> loading for common module")' isst_misc_reg() and isst_misc_unreg() can be
> simplified. Since these functions are only called during module_init()
> and module_exit() respectively, there is no contention while calling
> misc_register()/misc_deregister or isst_if_cpu_info_init()/
> isst_if_cpu_info_exit().
> 
> Hence remove mutex and reference counting.
> 
> Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
> ---
>  .../intel/speed_select_if/isst_if_common.c    | 42 +++++--------------
>  1 file changed, 11 insertions(+), 31 deletions(-)
> 
> diff --git a/drivers/platform/x86/intel/speed_select_if/isst_if_common.c b/drivers/platform/x86/intel/speed_select_if/isst_if_common.c
> index 3065f149e721..febfd5eeceb4 100644
> --- a/drivers/platform/x86/intel/speed_select_if/isst_if_common.c
> +++ b/drivers/platform/x86/intel/speed_select_if/isst_if_common.c
> @@ -651,10 +651,6 @@ static long isst_if_def_ioctl(struct file *file, unsigned int cmd,
>  
>  /* Lock to prevent module registration when already opened by user space */
>  static DEFINE_MUTEX(punit_misc_dev_open_lock);
> -/* Lock to allow one shared misc device for all ISST interfaces */
> -static DEFINE_MUTEX(punit_misc_dev_reg_lock);
> -static int misc_usage_count;
> -static int misc_device_ret;
>  static int misc_device_open;
>  
>  static int isst_if_open(struct inode *inode, struct file *file)
> @@ -720,39 +716,23 @@ static struct miscdevice isst_if_char_driver = {
>  
>  static int isst_misc_reg(void)
>  {
> -	mutex_lock(&punit_misc_dev_reg_lock);
> -	if (misc_device_ret)
> -		goto unlock_exit;
> -
> -	if (!misc_usage_count) {
> -		misc_device_ret = isst_if_cpu_info_init();
> -		if (misc_device_ret)
> -			goto unlock_exit;
> -
> -		misc_device_ret = misc_register(&isst_if_char_driver);
> -		if (misc_device_ret) {
> -			isst_if_cpu_info_exit();
> -			goto unlock_exit;
> -		}
> -	}
> -	misc_usage_count++;
> +	int ret;
>  
> -unlock_exit:
> -	mutex_unlock(&punit_misc_dev_reg_lock);
> +	ret = isst_if_cpu_info_init();
> +	if (ret)
> +		return ret;
>  
> -	return misc_device_ret;
> +	ret = misc_register(&isst_if_char_driver);
> +	if (ret)
> +		isst_if_cpu_info_exit();
> +
> +	return ret;
>  }
>  
>  static void isst_misc_unreg(void)
>  {
> -	mutex_lock(&punit_misc_dev_reg_lock);
> -	if (misc_usage_count)
> -		misc_usage_count--;
> -	if (!misc_usage_count && !misc_device_ret) {
> -		misc_deregister(&isst_if_char_driver);
> -		isst_if_cpu_info_exit();
> -	}
> -	mutex_unlock(&punit_misc_dev_reg_lock);
> +	misc_deregister(&isst_if_char_driver);
> +	isst_if_cpu_info_exit();
>  }
>  
>  /**
> 

Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>

-- 
 i.