Re: [PATCH v3 34/47] acpi: Register power-off handler with kernel power-off handler

[Rafael J. Wysocki]

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@xxxxxxxxxxxxx>
> Cc: Len Brown <lenb@xxxxxxxxxx>
> Signed-off-by: Guenter Roeck <linux@xxxxxxxxxxxx>
> ---
> 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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