On 04/03/2011 09:36 AM, Jim Cromie wrote: > 2011/3/29 Jürgen Lambrecht<J.Lambrecht@xxxxxxxxxxx>: >> 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> thanks, i'll use that to write a gpio driver for our own hw. > 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. > ok, interesting >> 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 ? It is ok now: i found it in arch/arm/plat-mxc/include/mach/gpio.h. Thanks, the backlight driver starts up now. Now I'm looking why udev (or mdev) does not create a /dev/fb0.. reading about it.. 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 _______________________________________________ Kernelnewbies mailing list Kernelnewbies@xxxxxxxxxxxxxxxxx http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
