On Wednesday, January 3, 2018 12:58:47 PM CET Ognjen Galic wrote:
> This is a patch that implements a generic hooking API for the
> generic ACPI battery driver.
>
> With this new generic API, drivers can expose platform specific
> behaviour via sysfs attributes in /sys/class/power_supply/BATn/
> in a generic way.
>
> A perfect example of the need for this API are Lenovo ThinkPads.
>
> Lenovo ThinkPads have a ACPI extension that allows the setting of
> start and stop charge thresholds in the EC and battery firmware
> via ACPI. The thinkpad_acpi module can use this API to expose
> sysfs attributes that it controls inside the ACPI battery driver
> sysfs tree, under /sys/class/power_supply/BATN/.
>
> The file drivers/acpi/battery.h has been moved to
> include/acpi/battery.h and the includes inside ac.c, sbs.c, and
> battery.c have been adjusted to reflect that.
>
> When drivers hooks into the API, the API calls add_battery() for
> each battery in the system that passes it a acpi_battery
> struct. Then, the drivers can use device_create_file() to create
> new sysfs attributes with that struct and identify the batteries
> for per-battery attributes.
>
> Signed-off-by: Ognjen Galic <smclt30p@xxxxxxxxx>
> ---
>
> Notes:
> v7:
> * Implemented mutual exclusion for hooking methods and battery
> callbacks
> * Fixed a BUG where errors in other modules would occur when the
> modules that depend on battery get unloaded
>
> v8:
> * Use list_for_each_safe instead of list_for_each for the module
> exit function where deletion of nodes occurs
>
> v9:
> * No changes in this patch in v9
>
> v10:
> * Fix compiler warnings in Intel's 0-day CI
>
> v11:
> * Fix changelog formatting
> * Make lists and mutex static
>
> v12:
> * Change all applicable list_for_each to list_for_each_entry
> * Define pr_fmt to include module name for pr_*
>
> drivers/acpi/ac.c | 2 +-
> drivers/acpi/battery.c | 151 ++++++++++++++++++++++++++++++++++++++++++++++++-
> drivers/acpi/battery.h | 11 ----
> drivers/acpi/sbs.c | 2 +-
> include/acpi/battery.h | 21 +++++++
> 5 files changed, 171 insertions(+), 16 deletions(-)
> delete mode 100644 drivers/acpi/battery.h
> create mode 100644 include/acpi/battery.h
>
> diff --git a/drivers/acpi/ac.c b/drivers/acpi/ac.c
> index 47a7ed5..2d8de2f 100644
> --- a/drivers/acpi/ac.c
> +++ b/drivers/acpi/ac.c
> @@ -33,7 +33,7 @@
> #include <linux/platform_device.h>
> #include <linux/power_supply.h>
> #include <linux/acpi.h>
> -#include "battery.h"
> +#include <acpi/battery.h>
>
> #define PREFIX "ACPI: "
>
> diff --git a/drivers/acpi/battery.c b/drivers/acpi/battery.c
> index 13e7b56..7089e31 100644
> --- a/drivers/acpi/battery.c
> +++ b/drivers/acpi/battery.c
> @@ -21,8 +21,12 @@
> * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> */
>
> +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
> +
> #include <linux/kernel.h>
> +#include <linux/list.h>
> #include <linux/module.h>
> +#include <linux/mutex.h>
> #include <linux/init.h>
> #include <linux/types.h>
> #include <linux/jiffies.h>
> @@ -42,7 +46,7 @@
> #include <linux/acpi.h>
> #include <linux/power_supply.h>
>
> -#include "battery.h"
> +#include <acpi/battery.h>
>
> #define PREFIX "ACPI: "
>
> @@ -124,6 +128,7 @@ struct acpi_battery {
> struct power_supply_desc bat_desc;
> struct acpi_device *device;
> struct notifier_block pm_nb;
> + struct list_head list;
> unsigned long update_time;
> int revision;
> int rate_now;
> @@ -626,6 +631,142 @@ static const struct device_attribute alarm_attr = {
> .store = acpi_battery_alarm_store,
> };
>
> +/*
> + * The Battery Hooking API
> + *
> + * This API is used inside other drivers that need to expose
> + * platform-specific behaviour within the generic driver in a
> + * generic way.
> + *
> + */
> +
> +static LIST_HEAD(acpi_battery_list);
> +static LIST_HEAD(battery_hook_list);
> +static DEFINE_MUTEX(hook_mutex);
> +
> +void __battery_hook_unregister(struct acpi_battery_hook *hook, int lock)
> +{
> + struct list_head *position;
> + struct acpi_battery *battery;
> + /*
> + * In order to remove a hook, we first need to
> + * de-register all the batteries that are registered.
> + */
> + if (lock)
> + mutex_lock(&hook_mutex);
> + list_for_each(position, &acpi_battery_list) {
> + battery = list_entry(position, struct acpi_battery, list);
> + hook->remove_battery(battery->bat);
> + }
> + list_del(&hook->list);
> + if (lock)
> + mutex_unlock(&hook_mutex);
> + pr_info("extension unregistered: %s\n", hook->name);
> +}
> +
> +void battery_hook_unregister(struct acpi_battery_hook *hook)
> +{
> + __battery_hook_unregister(hook, 1);
> +}
> +EXPORT_SYMBOL_GPL(battery_hook_unregister);
> +
> +void battery_hook_register(struct acpi_battery_hook *hook)
> +{
> + struct acpi_battery *battery;
> +
> + mutex_lock(&hook_mutex);
> + INIT_LIST_HEAD(&hook->list);
> + list_add(&hook->list, &battery_hook_list);
> + /*
> + * Now that the driver is registered, we need
> + * to notify the hook that a battery is available
> + * for each battery, so that the driver may add
> + * its attributes.
> + */
> + list_for_each_entry(battery, &acpi_battery_list, list) {
> + if (hook->add_battery(battery->bat)) {
> + /*
> + * If a add-battery returns non-zero,
> + * the registration of the extension has failed,
> + * and we will not add it to the list of loaded
> + * hooks.
> + */
> + pr_err("extension failed to load: %s",
> + hook->name);
> + __battery_hook_unregister(hook, 0);
> + return;
> + }
> + }
> + pr_info("new extension: %s\n", hook->name);
> + mutex_unlock(&hook_mutex);
> +}
> +EXPORT_SYMBOL_GPL(battery_hook_register);
> +
> +static void battery_hook_add_battery(struct acpi_battery *battery)
> +{
> + /*
> + * This function gets called right after the battery sysfs
> + * attributes have been added, so that the drivers that
> + * define custom sysfs attributes can add their own.
> + */
> + struct acpi_battery_hook *hook_node;
> +
> + mutex_lock(&hook_mutex);
> + INIT_LIST_HEAD(&battery->list);
> + list_add(&battery->list, &acpi_battery_list);
> + /*
> + * Since we added a new battery to the list, we need to
> + * iterate over the hooks and call add_battery for each
> + * hook that was registered. This usually happens
> + * when a battery gets hotplugged or initialized
> + * during the battery module initialization.
> + */
> + list_for_each_entry(hook_node, &battery_hook_list, list) {
> + if (hook_node->add_battery(battery->bat)) {
> + /*
> + * The notification of the extensions has failed, to
> + * prevent further errors we will unload the extension.
> + */
> + __battery_hook_unregister(hook_node, 0);
> + pr_err("error in extension, unloading: %s",
> + hook_node->name);
> + }
> + }
> + mutex_unlock(&hook_mutex);
> +}
> +
> +static void battery_hook_remove_battery(struct acpi_battery *battery)
> +{
> + struct acpi_battery_hook *hook;
> +
> + mutex_lock(&hook_mutex);
> + /*
> + * Before removing the hook, we need to remove all
> + * custom attributes from the battery.
> + */
> + list_for_each_entry(hook, &battery_hook_list, list) {
> + hook->remove_battery(battery->bat);
> + }
> + /* Then, just remove the battery from the list */
> + list_del(&battery->list);
> + mutex_unlock(&hook_mutex);
> +}
> +
> +static void __exit battery_hook_exit(void)
> +{
> + struct acpi_battery_hook *hook;
> + struct acpi_battery_hook *ptr;
> + /*
> + * At this point, the acpi_bus_unregister_driver
> + * has called remove for all batteries. We just
> + * need to remove the hooks.
> + */
> + list_for_each_entry_safe(hook, ptr, &battery_hook_list, list) {
> + __battery_hook_unregister(hook, 1);
> + }
> + mutex_destroy(&hook_mutex);
> +}
> +
> static int sysfs_add_battery(struct acpi_battery *battery)
> {
> struct power_supply_config psy_cfg = { .drv_data = battery, };
> @@ -647,6 +788,8 @@ static int sysfs_add_battery(struct acpi_battery *battery)
> battery->bat = power_supply_register_no_ws(&battery->device->dev,
> &battery->bat_desc, &psy_cfg);
>
> + battery_hook_add_battery(battery);
I seem to see a problem here, as this may be called before
battery_hook_register() in some cases if I'm not mistaken and there seems to
be nothing to ensure that the "hook" code will actually see the battery then.
Thanks,
Rafael
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