Re: [PATCH v4] gpio: lib-sysfs: Add 'wakeup' attribute

On Thu, Jan 15, 2015 at 11:49:49AM -0800, Soren Brinkmann wrote:

Add an attribute 'wakeup' to the GPIO sysfs interface which allows
marking/unmarking a GPIO as wake IRQ.
The file 'wakeup' is created in each exported GPIOs directory, if an IRQ
is associated with that GPIO and the irqchip implements set_wake().
Writing 'enabled' to that file will enable wake for that GPIO, while
writing 'disabled' will disable wake.
Reading that file will return either 'disabled' or 'enabled' depening on
the currently set flag for the GPIO's IRQ.

Signed-off-by: Soren Brinkmann <redacted>
Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>
---
Hi Linus, Johan,

I rebased my patch. And things look good.

I took at closer look at this patch now and I really don't think it
should be merged at all.

We have a mechanism for handling wake-up sources (documented in
Documentation/power/devices.txt) as well as an ABI to enable/disable
them using the power/wakeup device attribute from userspace.

Implementing proper wakeup support for unclaimed GPIOs would take some
work (if at all desired), but that is not a reason to be adding custom
implementations that violates the kernel's power policies and new ABIs
that would need to be maintained forever.

[ And we really shouldn't be adding anything to the broken gpio sysfs
interface until it's been redesigned. ]

Meanwhile you can (should) use gpio-keys if you need to wake your system
on gpio events.

But the 'is_visible' things does not behave the way I expected it to.
It seems to be only triggered on an export but not when attributes
change. Hence, in my case, everything was visiible since the inital
state matches that, but even when changing the direction or things
like that, attributes don't disappear. Is that something still worked
on? Expected

That's expected. We generally don't want attributes to appear or
disappear after the device has been registered (although there is a
mechanism for cases were it makes sense). This is no different from
how your v3 patch worked either.

Johan