linux-kernel - Re: [RFC][PATCH] gpiolib: add irq_wake (power-management) sysfs file

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Date:	Tue, 15 Nov 2011 13:16:37 +0000
From:	Mark Brown <broonie@...nsource.wolfsonmicro.com>
To:	Patrick Combes <p-combes@...com>
Cc:	grant.likely@...retlab.ca, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, Hugo Dupras <h-dupras@...com>
Subject: Re: [RFC][PATCH] gpiolib: add irq_wake (power-management) sysfs
 file

On Fri, Nov 11, 2011 at 10:40:06AM +0100, Patrick Combes wrote:

> By calling poll() on the /sys/class/gpio/gpioN/value sysfs file, usermode
> application can take benefit of gpio interrupts.
> However, depending on the power state reached, this interrupt may not wake-up
> the CPU.
> This patch creates a new sysfs file /sys/class/gpio/gpioN/irq_wake to enable
> usermode application to set the wake properties of a gpio IRQ.
> This option can be set or not for each gpio to preserve power consumption (e.g
> embedded systems).

There's already device global control for this in sysfs via the power
framework - 

Also...

> +	else if (sysfs_streq(buf, "enable") || sysfs_streq(buf, "1"))
> +		status = enable_irq_wake(gpio_to_irq(gpio));
> +	else if (sysfs_streq(buf, "disable") || sysfs_streq(buf, "0"))
> +		status = disable_irq_wake(gpio_to_irq(gpio));
> +	else
> +		status = -EINVAL;

...this doesn't do anything to stop userspace doing multiple enables and
disables.

> +	if (gpio_irq_data)
> +		status = sprintf(buf, " Wakeup %s\n",
> +					irqd_is_wakeup_set(gpio_irq_data)
> +					? " enable" : "disable");

This is *really* non-idiomatic for sysfs output, you'd expect the sysfs
output to look like the input.  It's supposed to machine parsable...
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