LinuxQuestions.org - [SOLVED] I/O error in code example from "Essential Linux Device Drivers"

- Linux - Kernel (https://www.linuxquestions.org/questions/linux-kernel-70/)

- - I/O error in code example from "Essential Linux Device Drivers" (https://www.linuxquestions.org/questions/linux-kernel-70/i-o-error-in-code-example-from-essential-linux-device-drivers-4175470197/)

I/O error in code example from "Essential Linux Device Drivers"

Hi,

I'm trying to run a code example from the book "Essential Linux Device Drivers". It's a driver module that's supposed to access the CMOS memory banks (port 0x70). Inserting the module fails with -EIO, which is caused by the following section of the code:

Code:

/* Request I/O region */

sprintf(cmos_devp[i]->name, "cmos%d", i);

if (!(request_region(addrports[i], 2, cmos_devp[i]->name))) {

    printk("cmos: I/O port 0x%x is not free.\n", addrports[i]);

    return -EIO;

}

My guess is that this fails because the memory region has been reserved already by the RTC driver (?). How can I fix the code? I'm using kernel version 3.2.46, the book code was written for a 2.6 kernel. I had to make some minor changes to get the code compiled.

Many thanks!

if you do not need the RTC driver then remove it. The port should become free. Else you will have to change the memory region.

Thanks, that did the trick! I removed the RTC driver from the kernel config and did a recompile. The kernel has a legacy RTC driver that can be compiled as a module. I used that driver as a replacement for the new driver, which cannot be modularized.