Then from user space using /sys/class/gpio sysfs interface, I can not make the pin to be gpio until I change the kernel code? -----Original Message----- From: Colin Cross [mailto:ccross@xxxxxxxxxx] Sent: Thursday, May 05, 2011 10:19 PM To: Laxman Dewangan Cc: linux-tegra@xxxxxxxxxxxxxxx; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx Subject: Re: Tegra gpio driver: Need to configure pins in gpio mode/nontristate with gpio-request On Thu, May 5, 2011 at 3:16 AM, Laxman Dewangan <ldewangan@xxxxxxxxxx> wrote: > Hi All, > When working on gpio driver for tegra, I found that gpio_request() does not > make the corresponding soc pins to gpio mode. It still keeps the pins in SFIO mode. > So we need to call two extra function along with gpio_request(): > Tegra_gpio_enable() and function for setting the pins in no non-tristate. > > Sue to this, the gpio sysfs interface does not work properly from user space /sys/class/gpio/. > To make the pin in gpio mode fom user space, need to have changes in kernel. > > I think the gpio_request() should make the pins to gpio mode and make ready for use. > Similarly gpio_free() should again put the pin into sfio mode with tristate disable. > > Please comment if there is any better way.. >From Documentation/gpio.txt: Note that requesting a GPIO does NOT cause it to be configured in any way; it just marks that GPIO as in use. Separate code must handle any pin setup (e.g. controlling which pin the GPIO uses, pullup/pulldown). -- To unsubscribe from this list: send the line "unsubscribe linux-tegra" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
