linux-device-driver

How to make a character device for i2c device, with open, close, ioctl etc. functions? I was looking for information about it last two weeks and couldn't find anything working. I found some information in Essential Linux Device Drivers, but it was written for 2.6 kernel, and i use 3.4.79 (i'm trying to write this driver for cubieboard2 on cubian distr) so this book has many deprecated functions, i tried to write my driver like there, but it still don't work (give me kernel errors while i'm truing to cat character device). Can anyone explain me what to do with it, or at least give me a working

I have a simple character device driver that allows you to read from a custom hardware device. It uses a DMA to copy data from the device's memory into kernel space (and then up to the user). The read call is very simple. It starts a DMA write, and then waits on a wait queue. When the DMA completes, the interrupt handler sets a flag and wakes up the wait queue. The important thing to note is that I can start the DMA at any time, even before the device has data to provide . The DMA engine will sit and wait until there is data to copy. This works well. I can implement a simple blocking read call

Currently, I am learning Linux device drivers. And got stuck over how opening a device file works ? What I got until now... Consider the a simple code that opens a normal file.. #incldue<stdio.h> int main() { FILE fp; char buffer[20]; fp = fopen(/home/yoggi/foo.txt, "r"); fread(buffer, 5, 1, fp); } In above program, The fopen(), c-library function, is a wrapper function to the system call open() , which intern calls sys_open() or file_open() in VFS layer function. As linux supports a number of file system, virtual file system then transfer the control to actual file system handler to the

I am trying to understand I2C client drivers. As per my understanding before registering I2C driver we have to define i2c_device_id table and device tree compatible table. I have following doubts. Could please help me to understand. 1) The definition of i2c_device_id structure contains two members ( name , driver_data ). The 1st member ( name ) is used to define the device name which will be used during driver binding, what is the use of the 2nd member ( driver_data ). 2) Driver binding will happen based on i2c_device_id table or device tree compatible string. Thanks in advance. 1) The

remap_pfn_range function (used in mmap call in driver) can be used to map kernel memory to user space. How is it done? Can anyone explain precise steps? Kernel Mode is a privileged mode (PM) while user space is non privileged (NPM). In PM CPU can access all memory while in NPM some memory is restricted - cannot be accessed by CPU. When remap_pfn_range is called, how is that range of memory which was restricted only to PM is now accessible to user space? Looking at remap_pfn_range code there is pgprot_t struct . This is protection mapping related struct. What is protection mapping? Is it the