Messages in this thread | | | Date | Mon, 21 Feb 2011 12:22:40 +0100 | From | Wolfram Sang <> | Subject | Re: [PATCH v2 1/4] gpiolib: Add "unknown" direction support |
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On Mon, Feb 21, 2011 at 12:07:27PM +0100, Alexander Stein wrote: > On Monday 21 February 2011, 10:47:56 Wolfram Sang wrote: > > > We had exported our 5V_enable gpio to sysfs to allow a user-space > > > application to enable/disable devices connected to 5V circuit. > > > But on the other hand we had to read the current status of this gpio in > > > the power-fail interrupt handler to distinguish between false-positive > > > (5V disabled) and a correct detection. > > > > What about gpio_export() (description in Documentation/gpio.txt)? > > Ah, I didn't know about this. I just expected this is only used from sysfs > part. But you have to make sure your .ko is loaded before userspace is > accessing sysfs and tries to export the GPIO.
Eh? Userspace doesn't export the GPIO in that case.
> Or is it "allowed" by the API convention to gpio_request and gpio_export (and > set direction) a GPIO in the machine startup code which will later be used in > a different place?
different place = userspace? Well, that's the main intention of gpio_export(). (I have the feeling we are missing each other here, thoguh) I'd suggest looking a bit further in the docs/code. It should make clear what is possible.
Regards,
Wolfram
-- Pengutronix e.K. | Wolfram Sang | Industrial Linux Solutions | http://www.pengutronix.de/ | [unhandled content-type:application/pgp-signature] | |