2011/3/29 Jürgen Lambrecht <J.Lambrecht@televic.com>:
Hello,
I am new to linux (coming from eCos). My backlight driver does not start up because the reset gpio pin is not correct specified. How does gpio work in Linux?
theres no single way. the new way is in drivers/gpio/* , implemented in gpiolib.c defined in #include <linux/gpio.h> there are also char drivers, with which Im more familiar. ./char/nsc_gpio.c ./char/pc8736x_gpio.c ./char/scx200_gpio.c
I have 2 platforms that use the same backlight driver, under arm, for freescale imx: imx31_3ds and imx27_3ds. I don't think that matters, I just need to understand the linux gpio.
The imx31 platform gives the number 88 as gpio number to the backlight driver. That number comes out of 'iomux-mx3.h'. In 'iomux-mx27.h' the GPIO's are specified in an other way, the "hardware" way, specifying bank and port. I think Linux GPIO needs a sort of general gpio number.
The problem here is that board IDs are somewhat arbitrary, whereas driver IDs are predictable. Take soekris 4801 as an example; it has gpio on the CPU-SOC (scx200_gpio), and on a peripheral chip (pc8736x_gpio) The board uses CPU pins for Leds (and reset button I think), but the GPIO exposed to connector is on pc87366 chip. The char drivers use major device numbers to select the chip & driver, and minor numbers to select the bank/pin on the chip. THis lets users create device files with suitable names / numbers.
But how do I calculate that number out of the datasheet? In the imx31 datasheet, I cannot find that number 88 (or the other numbers in 'iomux-mx3.h').
what driver supports your boards ? is it a new gpio driver ?
Kind regards, Jürgen
-- Jürgen Lambrecht R&D Associate Tel: +32 (0)51 303045 Fax: +32 (0)51 310670 http://www.televic-rail.com Televic Rail NV - Leo Bekaertlaan 1 - 8870 Izegem - Belgium Company number 0825.539.581 - RPR Kortrijk
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