How to use mpc8xxx_gpio.c device driver

[Ravi Gupta]

> Looking at the device tree for this board, it appears U-Boot remaps the
> IMMR registers to 0xe0000000. They are no longer accessible at
> 0xff400000.
>
> I would recommend studying arch/powerpc/boot/dts/mpc8377_rdb.dts in the
> Linux source code. That describes the device layout on your board after
> U-Boot has run.
>
> A wonderful tool for testing devices from userspace is "busybox devmem".
> It allows you to poke any physical address with any value. The output of
> "busybox devmem --help" should get you started. As a quick example,
> "busybox devmem 0xe0000c00 w 0x1" will write the 32-bit value 0x1 to
> address 0xe0000c00.
>
> I would also recommend using the built-in Linux GPIO API. It works, you
> just need to figure out how to use it. It will be much easier to get
> your code upstream if you use the provided APIs.
>
> The Documentation/gpio.txt file should help you in understanding the
> in-kernel Linux GPIO API. I'm afraid I don't have much experience other
> than accessing it via sysfs from userspace.
>
> Ira
>

Hi Ira,

Thanks for another great reply. Now I can also access gpio memory map
registers.

Thanks and Regards,
Ravi Gupta
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