linux-device-driver

I am using get_user_pages in a Linux kernel driver to pin memory for the purposes of [hardware] DMA. It all seems to work fine - but I am having a hard time proving that the "pinning" is doing the proper thing. When I inspect the flags on the physical pages after doing get_user_pages - the pages don't appear "locked" (as one might think they should be). In fact, I see no difference between the flags of otherwise "active" pages vs. those I have "pinned" via get_user_pages . The only difference I see is that get_user_pages has taken a refcount on the page. So I guess my question is - is holding

I am new to linux device drivers. I would like to know if there are man pages for the driver functions like register_chrdev. If yes, then how do I get them? Is there a package that I can download using apt-get? The Linux kernel pages in the man program reside in section 9, which is (un)fortunately a non-standard section. See this . Popular Linux distributions like Ubuntu don't distribute the man pages that fall under this section through their software channels (?). They're still available, for example, Debian provides one . There are also online versions of the man pages. Actually the kernel

Today I am getting started with developing Linux modules. It was rather hard to write, compile and work with Helloworld, but I've done it. My second module with open, write, read functions is ready, but I really dont know how to test it. Write method just makes printk(). My module is loaded, its name is iamnoob. How to test this write(...) function and to find smth in var/log/syslog? cat > iamnoob just writes a file to the dir. Same with cp and other. Sorry for noob question, i've googled, but no answer has been found. Sorry for poor English. A basic kernel module would normally include

I'm trying to be able to execute "make debug" at the command line and it will build my driver module with the -DDEBUG_OUTPUT define, which will cause certain sections of code to be compiled in. In 2.4 kernel makefiles, this is pretty easy. I just create a debug: target and included "-DDEBUG_OUTPUT" in the cc compilation command arguments for that target. Easy. Unfortunately (for me), 2.6 completely changed how modules are compiled, and I can ONLY seem to find the trivial "all" and "clean" examples, which don't show adding custom defines at compilation time. I tried this: debug: make -C $

In the function declaration int request_irq(unsigned int irq, irqreturn_t (*handler)(int, void *, struct pt_regs *), unsigned long irqflags, const char *devname, void *dev_id); Is dev_id an 'in' parameter or an 'out' parameter ? Where do we get this number from ? Dev_id is an input argument and must be globally unique. Normally the address of the device data structure is used as the Dev_id . It has value NULL if the interrupt line is NOT shared. It holds relevance only when the interrupt line is being shared. When it is shared, this parameter uniquely identifies the interrupt handler on the

I have a Linux kernel module that implements a character device driver. I've read through Linux Device Drivers and followed several tutorials. At this point, I have a simple module that provides open , release , and write file operations. I'm trying to use the Generic DMA Layer to create a streaming DMA mapping. I'm confused by the following excerpt from LDD: Many of the functions below require a struct device . This structure is the low-level representation of a device within the Linux device model. It is not something that drivers often have to work with directly, but you do need ot when