gpio driver user mode irq

lyf sci

Hi Experts,

As per my understanding the GPIO can be controlled from userspace using sysfs entries. If I would like to change the state of a GPIO ( For illustration, When key pressed switch ON LED when released switch OFF LED) based on the input state of another GPIO . The kernel code can written and registered for IRQ for the particular pin to achieve it but is there any user mode driver option to register an IRQ/signal/event handler to sense the input status of GPIO pin ?

over 11 years ago

0 Norman Wong over 11 years ago

Guru 26430 points

I assume you don't want to poll the input GPIO level from userspace. The kernel level GPIO IRQs are available to userspace vai sysfs. Depends on your kernel version. A kernel that supports userspace GPIO IRQ access will have sysfs exported files that include "edge" in addition to "direction", "input" and "output". You then need to use the linux system poll() function to wait on the GPIO input. The poll() function doesn't sound very efficient but it can put your waiting process to sleep allowing other processes to run. Also, you cannot miss a level change that userspace polling would miss if it is polling too slow.

0 Titusrathinaraj Stalin over 11 years ago

TI__Guru** 116100 points

Hi Lyf,

We need kernel module driver to register the IRQ for the particular GPIO and we can write GUI app (c++) to notify to user.

Try to configure the GPIO which is used as user switches on your EVM board.

Please refer to the following TI E2E posts.

http://e2e.ti.com/support/dsp/omap_applications_processors/f/42/p/324801/1132400.aspx

http://e2e.ti.com/support/embedded/linux/f/354/t/364623.aspx?pi196120=1

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gpio driver user mode irq