Tài liệu Linux Device Drivers-Chapter 3: Char Drivers docx

... 3: Char Drivers The goal of this chapter is to write a complete char device driver. We'll develop a character driver because this class is suitable for most simple hardware devices. Char ... /dev/$ {device} [0-3] major=`awk "\\$2==\"$module\" {print \\$1}" /proc/devices` mknod /dev/$ {device} 0 c $major 0 mknod /dev/$ {device} 1 c $major 1 mknod /dev/$ {device} 2 ... random-access device, one device or many, and so on. To make scull be useful as a template for writing real drivers for real devices, we'll show you how to implement several device abstractions...

Tài liệu Linux Device Drivers-Chapter 5 : Enhanced Char Driver Operations pptx

... Chapter 5 : Enhanced Char Driver Operations In Chapter 3, " ;Char Drivers& quot;, we built a complete device driver that the user can write to and read from. But a real device usually offers ... same device. Different device files will, for example, cause the drive to record with or without compression, or to automatically rewind the tape when the device is closed. Cloning the Device ... the same device) is best solved by implementing one device node for each access policy. An example of this practice can be found in the Linux tape driver, which provides multiple device files...

Tài liệu Linux Device Drivers-Chapter 1 :An Introduction to Device Drivers ppt

... 1 :An Introduction to Device Drivers As the popularity of the Linux system continues to grow, the interest in writing Linux device drivers steadily increases. Most of Linux is independent ... the open source nature of the Character devices A character (char) device is one that can be accessed as a stream of bytes (like a file); a char driver is in charge of implementing this behavior. ... by Linux, somebody somewhere has written a driver to make it work with the system. Without device drivers, there is no functioning system. Device drivers take on a special role in the Linux...

Tài liệu Linux Device Drivers-Chapter 2 : Building and Running Modules pptx

... to Device Drivers& quot;. #define MODULE #include < ;linux/ module.h> buffer-based graphics environments, where the X server acts only as a server based on a real kernel-space device ... users.  The most important devices can't be handled in user space, including, but not limited to, network interfaces and block devices. As you see, user-space drivers can't do that ... example, support for SCSI scanner devices (implemented by the SANE package) and CD writers (implemented by cdrecord and other tools). In both cases, user-level device drivers rely on If your code...

Tài liệu Linux Device Drivers-Chapter 4 : Debugging Techniques pptx

... Time for an example. Here is a simple read_procimplementation for the scull device: int scull_read_procmem (char *buf, char **start, off_t offset, int count, int *eof, void *data) { int ... in its read implementation: char faulty_buf[1024]; ssize_t faulty_read (struct file *filp, char *buf, size_t count, loff_t *pos) { int ret, ret2; char stack_buf[4]; printk(KERN_DEBUG ... limit; i++) { Scull_Dev *d = &scull_devices[i]; if (down_interruptible(&d->sem)) return -ERESTARTSYS; len += sprintf(buf+len,"\nDevice %i: qset %i, q %i, sz %li\n",...

Tài liệu Linux Device Drivers-Chapter 6 : Flow of Time pptx

... #include < ;linux/ delay.h> void udelay(unsigned long usecs); Chapter 6 : Flow of Time At this point, we know the basics of how to write a full-featured char module. Real-world drivers, however, ... available in Linux 2.0, sysdep.h fills the gap. Task Queues One feature many drivers need is the ability to schedule execution of some tasks at a later time without resorting to interrupts. Linux ... introduced the following symbols: #include < ;linux/ param.h> HZ The HZ symbol specifies the number of clock ticks generated per second. #include < ;linux/ sched.h> volatile unsigned long...

Tài liệu Linux Device Drivers-Chapter 7 : Getting Hold of Memory doc

... that describes the allocation interface it offers to device drivers. The Zoran 36120 frame grabber driver, part of the 2.4 kernel (in drivers /char/ zr36120.c) uses the bigphysarea extension if ... GFP_KERNEL and GFP_ATOMIC, although those two cover most of the needs of device drivers. All the flags are defined in < ;linux/ mm.h>: individual flags are prefixed with a double underscore, ... happens, the Linux kernel takes advantage of the feature, and both the kernel and get_free_pages addresses lie in one of those memory ranges. The difference is transparent to device drivers and...

Tài liệu Linux Device Drivers-Chapter 8 :Hardware Management docx

... scull and similar toys is a good introduction to the software interface of a Linux device driver, implementing a real device requires hardware. The driver is the abstraction layer between software ... easy to use. I/O Ports and I/O Memory Every peripheral device is controlled by writing and reading its registers. Most of the time a device has several registers, and they are accessed at These ... 32-bit (maximum) data path. The functions just described are primarily meant to be used by device drivers, but they can also be used from user space, at least on PC-class computers. The GNU...

Tài liệu Linux Device Drivers-Chapter 9 :Interrupt Handling Although doc

... :Interrupt Handling Although some devices can be controlled using nothing but their I/O regions, most real-world devices are a bit more complicated than that. Devices have to deal with the external ... can explicitly be shared. So Linux supports shared interrupts and on all buses where it makes any sense, not just the PCI. Thus, suitably aware drivers for ISA devices can also share an IRQ ... interrupt line, the peripheral device asserts the IRQ signal until software clears the pending interrupt (usually by writing to a device register); therefore, if several devices pull the line active,...

Tài liệu Linux Device Drivers-Chapter 10 :Judicious Use of Data Types doc

... portability issues. Modern versions of the Linux kernel are highly portable, running on several very different architectures. Given the multiplatform nature of Linux, drivers intended for serious use ... demonstrated by running the program on different Linux computers: arch Size: char shor int long ptr long-long u8 u16 u32 u64 } The < ;linux/ list.h> file also defines a macro list_for_each ... itself. See the include file for the rest. Not all Linux versions defined all the macros that deal with byte ordering. In particular, the linux/ byteorderdirectory appeared in version 2.1.72...

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