RE: Compile program using XGpio

Hi Bruno,

If you're needing a GPIO driver (not wanting to write one) we have one
in the development branch of our GIT tree that's working.  This is
arch/powerpc only, no arch/ppc.

You could use it for turning LEDS on as I just tested it and updated the
wiki to show how to use it from user space.  There is also an LED driver
that is in the kernel that sits on top of a GPIO driver specifically for
LEDs.

http://xilinx.wikidot.com/osl-gpio-driver

Thanks,
John

-----Original Message-----
From: Grant Likely [mailto:grant.likely@secretlab.ca]
Sent: Thursday, October 23, 2008 11:46 AM
To: Bruno Monteiro
Cc: John Linn; linuxppc-embedded@ozlabs.org
Subject: Re: Compile program using XGpio
=

On Thu, Oct 23, 2008 at 10:58 AM, Bruno Monteiro

[off-list ref] wrote:

quoted

Hi,

I'm a new driver writer and i'm trying to understand how to deal

with XGpio.

quoted

My goal is writing a small piece of code that can turn leds on and

off. I

quoted

think this driver should do it:


#include <linux/init.h>
#include <linux/module.h>

#include "xgpio.h"
#include "xgpio_ioctl.h"
#include "xparameters.h"

XGpio led;

static int myteste_init(void)
{
    XGpio_Initialize (&led, LEDs_4Bit);
    XGpio_SetDataDirection(&led,1,0);
    XGpio_DiscreteWrite(&led,1,0xf);
    printk (KERN_ALERT "LEDS: Turn off\n");

    return 0;
}

static int myteste_exit(void)
{

    XGpio_DiscreteWrite(&led,1,0x0);
    printk (KERN_ALERT "LEDS: Turn on\n");
    return 0;
}

module_init(myteste_init);
module_exit(myteste_exit);

But i have this error:
ERROR: "XGpio_SetDataDirection" [drivers/char/mytest/mytest.ko]

undefined!

quoted

ERROR: "XGpio_Initialize" [drivers/char/mytest/mytest.ko] undefined!
ERROR: "XGpio_DiscreteWrite" [drivers/char/mytest/mytest.ko]

undefined!

=

None of the XGpio functions are available in Linux.  You need to use
the Linux kernel memory access functions instead (in_be32() and
out_be32()).
=

You also need to use the ioremap() function to map the physical
address of the GPIO block into a virtual address that the kernel can
use:
=

ie:
static int myteste_init(void)
{
    u32 __iomem *regs;
=

    regs =3D ioremap([address of GPIO block], 0x100);
    if (regs =3D=3D NULL)
        return -ENOMEM;
=

    /* configure as output */
    out_be32(regs + 4, 0);
    /* turn on leds */
    out_be32(regs, 0);
    printk (KERN_ALERT "LEDS: Turn on\n");
    return 0;
}
=

This is just a simple example though.  You should follow the pattern
of other device drivers and bind against the of_platform_bus so your
device can be described in the device tree (.dts) file.
=

Or, better yet, use the existing driver from the Xilinx linux-2.6 git

tree.

=

g.
=

--
Grant Likely, B.Sc., P.Eng.
Secret Lab Technologies Ltd.

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