Re: [PATCH v4 3/4] pmdomain: core: add genpd_for_each_child() helper

On 26-08-19 10:08:38, Kevin Hilman (TI) wrote:
> Add a new internal helper function genpd_for_each_child() that recursively
> iterates over all devices in a PM domain and its child domains (subdomains).
> This helper is useful for governors and other core PM domain code that needs
> to examine or apply operations to all devices within a domain hierarchy.
> 
> The function takes a callback that is invoked for each device, and supports
> early termination if the callback returns a non-zero value.
> 
> The helper is defined in a new internal header drivers/pmdomain/core.h and
> implemented in drivers/pmdomain/core.c, making it available to other PM
> domain subsystem components.
> 
> The first user of this helper is the cpu_system_power_down_ok() governor
> function, which uses it to check device QoS latency constraints across the
> entire domain hierarchy.
> 
> Signed-off-by: Kevin Hilman (TI) <[email protected]>
> ---
>  drivers/pmdomain/core.c | 45 +++++++++++++++++++++++++++++++++++++++++++++
>  drivers/pmdomain/core.h | 17 +++++++++++++++++
>  2 files changed, 62 insertions(+)
> 
> diff --git a/drivers/pmdomain/core.c b/drivers/pmdomain/core.c
> index 842c4169e290..ff27369d9a97 100644
> --- a/drivers/pmdomain/core.c
> +++ b/drivers/pmdomain/core.c
> @@ -24,6 +24,8 @@
>  #include <linux/cpu.h>
>  #include <linux/debugfs.h>
>  
> +#include "core.h"
> +
>  /* Provides a unique ID for each genpd device */
>  static DEFINE_IDA(genpd_ida);
>  
> @@ -276,6 +278,49 @@ static void genpd_sd_counter_inc(struct generic_pm_domain *genpd)
>  	smp_mb__after_atomic();
>  }
>  
> +/**
> + * genpd_for_each_child - Recursively iterate over all devices
> + *                        in a PM domain and its subdomains.
> + * @genpd: PM domain to iterate over.
> + * @fn: Callback function to invoke for each device.
> + * @data: Data to pass to the callback function.
> + *
> + * This function recursively walks through all devices in the given PM domain
> + * and all devices in its child PM domains (subdomains). For each device found,
> + * the callback function @fn is invoked with the device and @data as arguments.
> + *
> + * Note: this function is inteded for use by the core and governors,
> + * not for pmdomain providers.
> + *
> + * Returns: 0 on success, or the first non-zero value returned by @fn.
> + */
> +int genpd_for_each_child(struct generic_pm_domain *genpd,
> +			 int (*fn)(struct device *dev, void *data),
> +			 void *data)
> +{
> +	struct pm_domain_data *pdd;
> +	struct gpd_link *link;
> +	int ret;
> +
> +	/* First, iterate over all devices in this domain */
> +	list_for_each_entry(pdd, &genpd->dev_list, list_node) {
> +		ret = fn(pdd->dev, data);
> +		if (ret)
> +			return ret;
> +	}
> +
> +	/* Then, recursively iterate over all child domains (subdomains) */
> +	list_for_each_entry(link, &genpd->parent_links, parent_node) {
> +		struct generic_pm_domain *child_pd = link->child;
> +
> +		ret = genpd_for_each_child(child_pd, fn, data);
> +		if (ret)
> +			return ret;
> +	}
> +
> +	return 0;
> +}

This is usefull, I like it.

> +
>  #ifdef CONFIG_DEBUG_FS
>  static struct dentry *genpd_debugfs_dir;
>  
> diff --git a/drivers/pmdomain/core.h b/drivers/pmdomain/core.h
> new file mode 100644
> index 000000000000..7061891d31fb
> --- /dev/null
> +++ b/drivers/pmdomain/core.h
> @@ -0,0 +1,17 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * Internal header for PM domain core
> + *
> + * Copyright (C) 2011 Rafael J. Wysocki <[email protected]>, Renesas Electronics Corp.
> + */

Year and author are wrong.

With this addressed:

Reviewed-by: Abel Vesa <[email protected]>