linux-kernel - Re: [PATCH 20/36] cpufreq: amd-pstate: move to use bus_get_dev

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Date:   Tue, 14 Mar 2023 14:04:10 +0800
From:   Huang Rui <ray.huang@....com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "rafael@...nel.org" <rafael@...nel.org>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        "linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>
Subject: Re: [PATCH 20/36] cpufreq: amd-pstate: move to use bus_get_dev_root()

On Tue, Mar 14, 2023 at 02:29:02AM +0800, Greg Kroah-Hartman wrote:
> Direct access to the struct bus_type dev_root pointer is going away soon
> so replace that with a call to bus_get_dev_root() instead, which is what
> it is there for.
> 
> In doing so, remove the unneded kobject structure that was only being
> created to cause a subdirectory for the attributes.  The name of the
> attribute group is the correct way to do this, saving code and
> complexity as well as allowing the attributes to properly show up to
> userspace tools (the raw kobject would not allow that.)
> 
> Cc: Huang Rui <ray.huang@....com>
> Cc: "Rafael J. Wysocki" <rafael@...nel.org>
> Cc: Viresh Kumar <viresh.kumar@...aro.org>
> Cc: linux-pm@...r.kernel.org
> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> ---
> Note, this is a patch that is a prepatory cleanup as part of a larger
> series of patches that is working on resolving some old driver core
> design mistakes.  It will build and apply cleanly on top of 6.3-rc2 on
> its own, but I'd prefer if I could take it through my driver-core tree
> so that the driver core changes can be taken through there for 6.4-rc1.

Thanks Greg.

Acked-by: Huang Rui <ray.huang@...d.com>

> 
>  drivers/cpufreq/amd-pstate.c | 24 ++++++++++--------------
>  1 file changed, 10 insertions(+), 14 deletions(-)
> 
> diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
> index 73c7643b2697..b92454c50118 100644
> --- a/drivers/cpufreq/amd-pstate.c
> +++ b/drivers/cpufreq/amd-pstate.c
> @@ -63,7 +63,6 @@ static struct cpufreq_driver *current_pstate_driver;
>  static struct cpufreq_driver amd_pstate_driver;
>  static struct cpufreq_driver amd_pstate_epp_driver;
>  static int cppc_state = AMD_PSTATE_DISABLE;
> -struct kobject *amd_pstate_kobj;
>  
>  /*
>   * AMD Energy Preference Performance (EPP)
> @@ -932,6 +931,7 @@ static struct attribute *pstate_global_attributes[] = {
>  };
>  
>  static const struct attribute_group amd_pstate_global_attr_group = {
> +	.name = "amd_pstate",
>  	.attrs = pstate_global_attributes,
>  };
>  
> @@ -1253,6 +1253,7 @@ static struct cpufreq_driver amd_pstate_epp_driver = {
>  
>  static int __init amd_pstate_init(void)
>  {
> +	struct device *dev_root;
>  	int ret;
>  
>  	if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD)
> @@ -1299,24 +1300,19 @@ static int __init amd_pstate_init(void)
>  	if (ret)
>  		pr_err("failed to register with return %d\n", ret);
>  
> -	amd_pstate_kobj = kobject_create_and_add("amd_pstate", &cpu_subsys.dev_root->kobj);
> -	if (!amd_pstate_kobj) {
> -		ret = -EINVAL;
> -		pr_err("global sysfs registration failed.\n");
> -		goto kobject_free;
> -	}
> -
> -	ret = sysfs_create_group(amd_pstate_kobj, &amd_pstate_global_attr_group);
> -	if (ret) {
> -		pr_err("sysfs attribute export failed with error %d.\n", ret);
> -		goto global_attr_free;
> +	dev_root = bus_get_dev_root(&cpu_subsys);
> +	if (dev_root) {
> +		ret = sysfs_create_group(&dev_root->kobj, &amd_pstate_global_attr_group);
> +		put_device(dev_root);
> +		if (ret) {
> +			pr_err("sysfs attribute export failed with error %d.\n", ret);
> +			goto global_attr_free;
> +		}
>  	}
>  
>  	return ret;
>  
>  global_attr_free:
> -	kobject_put(amd_pstate_kobj);
> -kobject_free:
>  	cpufreq_unregister_driver(current_pstate_driver);
>  	return ret;
>  }
> -- 
> 2.39.2
>