Re: Compile program using XGpio

On Thu, Oct 23, 2008 at 10:58 AM, Bruno Monteiro [off-list ref] wrote:

Hi,

I'm a new driver writer and i'm trying to understand how to deal with XGpio.
My goal is writing a small piece of code that can turn leds on and off. I
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!
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 = ioremap([address of GPIO block], 0x100);
    if (regs == 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.