Find a power_supply of type

Question

My kernel driver needs to access battery's properties (get_property, set_property).
Problem: How to find the battery's struct power_supply?

I only find power_supply_get_by_name but there can be different names for the battery. I need to check the power_supply's type but this is where I am stuck.

A direct get_by_type or a get_all_power_supplies to check the type on my own or also a get_power_supply_names to pass to power_supply_get_by_name would be fine for me.

I want to avoid file accesses in the kernel so what is a better way to find the type="battery" power_supply?

I suspect I should grab the supply every time again because it may change or vanish / reappear? This driver can access the supply every couple of seconds in some situations so it would be nice to not spend a long time finding the battery.

Answer 1

Exactly a year late for the party. :) Here's the basic idea that loops over the all objects of power-supply class.

#include <linux/power_supply.h>

static int power_supply_printer(struct device *dev, const void *data)
{
    struct power_supply *psy = dev_get_drvdata(dev);

    (void)data;
    printk(KERN_INF "power-supply = %s\n", psy->desc->name);

    /* Return 1 if found, 0 if this is not valid. */
    return 0;
}

static __init int my_driver_init(void)
{
    struct device *dev;

    dev = class_find_device(power_supply_class, NULL, NULL /* data*/, power_supply_printer);
    ...
}

This function will iterate over all power_suppy_class drivers. Note, as long as the call-back function returns 0, it will check the next available device in that class.