developing linux device drivers pdf

Ngày tải lên: 21/01/2014, 07:20

... 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 ... independent of the devices attached to the SCSI cable. Other classes of device drivers have been added to the kernel in recent times, including USB drivers, FireWire drivers, and I2O drivers. In ... 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...

Ngày tải lên: 24/12/2013, 01:17

... implementations. For example, the video-for -linux set of drivers is split into a generic module that exports symbols used by lower- level device drivers for specific hardware. According to your ... new device, it will be able to avoid probing those ports that are already in use by other drivers. ISA probing is in fact a risky task, and several drivers distributed with the official Linux ... not belong to any of the classes listed in "Classes of Devices and Modules" in Chapter 1, "An Introduction to Device Drivers& quot;. The sample driver shown in this chapter is called...

Ngày tải lên: 24/12/2013, 01:17

... of setting up the devices. for (i=0; i < scull_nr_devs; i++) { scull_devices[i].quantum = scull_quantum; scull_devices[i].qset = scull_qset; sema_init(&scull_devices[i].sem, 1); ... Allocation of Major Numbers Some major device numbers are statically assigned to the most common devices. A list of those devices can be found in Documentation/devices.txt within the kernel source ... actually knows the name of the device being opened, just the device number and users can play on this indifference to names by aliasing new names to a single device for their own convenience....

Ngày tải lên: 24/12/2013, 01:17

... /proc is heavily used in the Linux system. Many utilities on a modern Linux distribution, such as ps, top, and uptime, get their information from /proc. Some device drivers also export information ... } exit(0); } setconsole uses the special ioctl command TIOCLINUX, which implements Linux- specific functions. To use TIOCLINUX, you pass it an argument that is a pointer to a byte array. ... 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",...

Ngày tải lên: 24/12/2013, 01:17

... implementing device control this way is that the user can control the device just by writing data, without needing to use (or sometimes write) programs built just for configuring the device. For ... on the device, but some other operations should be denied. For example, not all users of a tape drive should be able to set its default block size, and the ability to work with a disk device ... cannot change the baud rate by writing to the device. That is what ioctl is for: controlling the I/O channel. Another important feature of real devices (unlike scull) is that data being read...

Ngày tải lên: 24/12/2013, 01:17

... gettime: 846157215.942465 xtime: 846157215.941188 jiffies: 1308095 Delaying Execution Device drivers often need to delay the execution of a particular piece of code for a period of time ... according to the value of HZ, which is an architecture-dependent value defined in < ;linux/ param.h>. Current Linux versions define HZ to be 100 for most platforms, but some platforms use 1024, ... "Interrupt Handling". For now, suffice it to say that a bottom half is a mechanism provided by a device driver to handle asynchronous tasks which, usually, are too large to be done while handling...

Ngày tải lên: 24/12/2013, 01:17

... cache. Device drivers normally do not exhibit the sort of memory behavior that justifies using a lookaside cache, but there can be exceptions; the USB and ISDN drivers in Linux 2.4 use caches. Linux ... 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, ... freeing of memory. The Linux kernel offers a richer set of memory allocation primitives, however. In this chapter we look at other ways of making use of memory in device drivers and at how to...

Ngày tải lên: 24/12/2013, 01:17

... ports are: #include < ;linux/ ioport.h> can be either hardwired in the device or assigned by system firmware at boot time. The former is true, for example, of ISA devices, whose addresses ... addresses are either burned in device logic circuits, statically assigned in local device memory, or set by means of physical jumpers. The latter is true of PCI devices, whose addresses are assigned ... written to device memory, where they persist only while the device is powered on. Either way, for software to access I/O memory, there must be a way to assign a virtual address to the device. ...

Ngày tải lên: 24/12/2013, 01:17

... long as you don't use the two devices at the same time. It is quite common for users to load the module for a special device at system boot, even if the device is rarely used. A data acquisition ... :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 ... pointer to your device data structure in dev_id, so a driver that manages several instances of the same device doesn't need any extra code in the interrupt handler to find out which device is...

Ngày tải lên: 24/12/2013, 01:17

... 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 ... program on different Linux computers: arch Size: char shor int long ptr long- long u8 u16 u32 u64 There are dozens of similar routines; you can see the full list in < ;linux/ byteorder/big_endian.h> ... 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...

Ngày tải lên: 24/12/2013, 01:17

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