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> 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 > > > _______________________________________________ > Kernelnewbies mailing list > Kernelnewbies@xxxxxxxxxxxxxxxxx > http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies > _______________________________________________ Kernelnewbies mailing list Kernelnewbies@xxxxxxxxxxxxxxxxx http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
