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SubjectRe: [PATCH v3 34/47] acpi: Register power-off handler with kernel power-off handler
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On Monday, October 27, 2014 08:55:41 AM Guenter Roeck wrote:
> Register with kernel power-off handler instead of setting pm_power_off
> directly. Register with high priority to reflect that the driver explicitly
> overrides existing power-off handlers.

Well, I'm still rather unconvinced that notifiers are particularly suitable for
this purpose.

Specifically ->

> Cc: Rafael J. Wysocki <rjw@rjwysocki.net>
> Cc: Len Brown <lenb@kernel.org>
> Signed-off-by: Guenter Roeck <linux@roeck-us.net>
> ---
> v3:
> - Replace poweroff in all newly introduced variables and in text
> with power_off or power-off as appropriate
> - Replace POWEROFF_PRIORITY_xxx with POWER_OFF_PRIORITY_xxx
> - Replace acpi: with ACPI: in log message
> v2:
> - Use define to specify poweroff handler priority
> - Use pr_warn instead of pr_err
>
> drivers/acpi/sleep.c | 15 +++++++++++++--
> 1 file changed, 13 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/acpi/sleep.c b/drivers/acpi/sleep.c
> index 05a31b5..7875b92 100644
> --- a/drivers/acpi/sleep.c
> +++ b/drivers/acpi/sleep.c
> @@ -16,6 +16,8 @@
> #include <linux/device.h>
> #include <linux/interrupt.h>
> #include <linux/suspend.h>
> +#include <linux/notifier.h>
> +#include <linux/pm.h>
> #include <linux/reboot.h>
> #include <linux/acpi.h>
> #include <linux/module.h>
> @@ -827,14 +829,22 @@ static void acpi_power_off_prepare(void)
> acpi_disable_all_gpes();
> }
>
> -static void acpi_power_off(void)
> +static int acpi_power_off(struct notifier_block *this,
> + unsigned long unused1, void *unused2)
> {

-> Is there any reason why any notifier in the new chain would use the
second argument for anything meaningful? And the third argument for
that matter?

> /* acpi_sleep_prepare(ACPI_STATE_S5) should have already been called */
> printk(KERN_DEBUG "%s called\n", __func__);
> local_irq_disable();
> acpi_enter_sleep_state(ACPI_STATE_S5);
> +
> + return NOTIFY_DONE;

Also is there any reason for any notifier in the new chain to return anything
different from NOTIFY_DONE and if so, then what happens when anything else
is returned?

> }
>
> +static struct notifier_block acpi_power_off_nb = {
> + .notifier_call = acpi_power_off,
> + .priority = POWER_OFF_PRIORITY_HIGH,
> +};
> +
> int __init acpi_sleep_init(void)
> {
> char supported[ACPI_S_STATE_COUNT * 3 + 1];
> @@ -851,7 +861,8 @@ int __init acpi_sleep_init(void)
> if (acpi_sleep_state_supported(ACPI_STATE_S5)) {
> sleep_states[ACPI_STATE_S5] = 1;
> pm_power_off_prepare = acpi_power_off_prepare;
> - pm_power_off = acpi_power_off;
> + if (register_power_off_handler(&acpi_power_off_nb))
> + pr_warn("ACPI: Failed to register power-off handler\n");
> }
>
> supported[0] = 0;
>

--
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.


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