深入理解Linux驱动中的Timer机制 (linux 驱动 timer)
Timer是在Linux内核中非常重要的机制之一，它被广泛应用于各种驱动程序的实现中。在系统中，Timer的作用是用来定期触发系统任务的执行，比如定期回收缓存、轮询数据、定时唤醒等。在本文中，我们将深入探讨Linux驱动中的Timer机制，包括Timer的概念、实现方式以及应用场景等。
一、概念
Timer是一个时间定时器，它是Linux内核内置的一种机制。在内核中，每个Timer都有一个到期时间，当时间到期时，该Timer会向内核注册的回调函数发送信号。这个回调函数通常是驱动程序中的处理函数，它会根据这个信号来做相应的处理。在Linux驱动中，Timer被广泛用于周期性地执行一些任务，比如检查硬件状态、轮询数据、定期回收缓存等。
二、实现方式
在Linux内核中，Timer有两种实现方式，一种是使用软中断(SoftIRQ)来实现的，另一种是使用工作队列(Work Queue)来实现的。
1.软中断
软中断是Linux内核的一种机制，它是一种异步的、软件级别的、低优先级的中断。当CPU在执行用户空间程序时，软中断可以立即打断该程序的执行，让内核处理一些高优先级的任务。软中断使用的是内核线程(kernel thread)的上下文，该线程会在软中断发生时自动调度执行。
在使用软中断实现Timer时，内核会为每个Timer创建一个相应的软中断。当Timer到期时，软中断会被触发，内核会调用回调函数执行相应的任务。在Linux内核中，软中断的优先级相对较低，因此如果需要高实时性，建议使用工作队列来实现。
2.工作队列
工作队列是Linux内核提供的一种异步执行机制，它主要用于处理一些低优先级、非实时的任务。工作队列使用的是内核线程(kernel thread)的上下文，它们的执行顺序是不可预测的，但是可以确保任务得到执行。
在使用工作队列实现Timer时，驱动程序会创建一个相应的工作队列。当Timer到期时，工作队列会被触发并立即执行相应的任务，驱动程序可以通过工作队列来实现一些周期性的任务。
三、应用场景
Timer机制在Linux驱动中有着广泛的应用场景，主要包括以下几个方面：
1.定期检查硬件状态
比如一些设备需要周期性地检查自身的状态，比如磁盘读写状态、网络连接状态等。驱动程序可以使用Timer来实现这个功能，定期检查设备状态并向内核发送状态变化的信号。
2.轮询数据
比如一些输入设备需要轮询输入状态，比如键盘、鼠标等。驱动程序可以使用Timer来实现轮询功能，定期检查输入设备的状态并通知内核有新的输入事件发生。
3.定期回收缓存
系统中会有一些内存缓存用来存储一些临时数据，这些数据需要定期回收。驱动程序可以使用Timer来实现定期回收缓存的功能，避免内存泄漏等问题。
4.定时唤醒
在一些省电的场景下，设备需要在一段时间后唤醒执行任务。驱动程序可以使用Timer来实现定时唤醒的功能，保证设备在需要执行任务时能够被唤醒。
Timer是Linux驱动中非常重要的机制之一，它通常被用来周期性地执行一些任务。在内核中，Timer有两种实现方式，一种是使用软中断(SoftIRQ)来实现的，另一种是使用工作队列(Work Queue)来实现的。应用场景包括定期检查硬件状态、轮询数据、定期回收缓存、定时唤醒等。熟悉Timer机制对于Linux驱动程序员来说非常重要，它可以帮助他们更好地实现设备驱动程序及相关应用。
相关问题拓展阅读：
linux0.11版本中，关于函数do_timer的疑问
可以去作者论坛提问 oldlinux.org
void do_timer (long cpl){
…
fn = next_timer->fn;
next_timer->fn = NULL;
next_timer = next_timer->next;
(fn)();
…
}
这个函数中的函数指针是在函数void add_timer(long jiffies, void (*fn)(void))中添加的。这个腔厅函数是供内核使用的，用户空间的函数是不能调用add_timer的，也就是说 do_timer (long cpl)函数中的函数指针只会指向内核里面的函数。
（我去看了linux0.11的源码，用的地方确实只有
Floppy.c (kernel\blk_drv):add_timer(2,&transfer);
Floppy.c (kernel\blk_drv):add_timer(ticks_to_floppy_on(current_drive),&floppy_on_interrupt);
Sched.c (kernel):void add_timer(long jiffies, void (*fn)(void))
Sched.h (include\linux):extern void add_timer(long jiffies, void (*fn)(void));
）
所以的你的“内核不能直接访问用户空州冲间函数问题”是不存在的。
我也是看到了
这个帖子才想到的册圆歼。
刚开始学这个，可能说的不对，多包涵。
楼主你好，我也有相同的困惑，不知道你这个最后找到最终的解释了没？
在LINUX中如何加载驱动网卡
实现是通过虚拟网卡实现的。
若想加载USB无启盯线网卡，只需要把这个USB设备和host切断联系，虚歼旁闷拟机的Linux可以自氏弯动的接管这个USB设备。
就在虚拟机下面的状态栏上可以控制设备归谁管理。
直接找好对应的驱动 一般都会有readme 或者install 之类的说明文兄岩毁档来告诉你如何去安装这个网羡备卡驱动的
Linux* Base Driver for the Atheros(R) AR8121/AR8113 PCI-E Ethernet Adapter
==========================================================================
Contents
========
– In This Release
– Building and Installation
– Command Line Parameters
– Additional Configurations
– Known Issues
– Support
In This Release
===============
This file describes the Linux* Base Driver for the Atheros(R) AR8121/AR8113 PCI-E
Ethernet Adapter, version 1.0.0.5 This driver supports the 2.4.x and 2.6.x kernels.
This driver is only supported as a loadable module at this time. Atheros is not
supplying patches against the kernel source to allow for static linking of
the driver. For questions related to hardware requirements, refer to the
documentation supplied with your Atheros(R) adapter. All hardware
requirements listed apply to use with Linux.
Building and Installation
=========================
To build a binary RPM* package of this driver, run ‘rpmbuild -tb
‘. Replace with the specific filename of
the driver.
NOTE: For the build to work properly, the currently running kernel MUST match
the version and configuration of the installed kernel sources. If you
have just recompiled the kernel reboot the system now.
RPM functionality has only been tested in Red Hat distributions.
1. Move the base driver tar file to the directory of your choice. For example,
use /home/username/arl1e or /usr/local/src/枣唯arl1e.
2. Untar/unzip archive:
tar zxf arl1e-x.x.x.x.tar.gz
3. Change to the driver src directory:
cd arl1e-x.x.x.x/src/
4. Compile the driver module:
make install
The binary will be installed as:
/lib/modules//kernel/drivers/net/arl1e.o
The install locations listed above are the default locations. They might
not be correct for certain Linux distributions. For more information,
see the ldistrib.txt file included in the driver tar.
5. Install the module:
inod arl1e =
6. Assign an IP address to the interface by entering the following, where
x is the interface number:
ifconfig ethx
7. Verify that the interface works. Enter the following, where
is the IP address for another machine on the same subnet as the interface
that is being tested:
ping
Command Line Parameters
=======================
If the driver is built as a module, the following optional parameters are
used by entering them on the command line with the modprobe or inod command
using this syntax:
modprobe arl1e
inod arl1e
For example, with two L001 PCIE adapters, entering:
inod arl1e TxMemSize=80,128
loads the arl1e driver with 8KB TX memory for the first adapter and 10KB TX memory
for the second adapter.
The default value for each parameter is generally the recommended setting,
unless otherwise noted.
NOTES: A descriptor describes a data buffer and attributes related to the
data buffer. This information is accessed by the hardware.
media_type
Valid Range: 0-4
auto-negotiate at all supported speeds
only link at 1000Mbps Full Duplex
only link at 100Mbps Full Duplex
only link at 100Mbps Half Duplex
only link at 10Mbps Full Duplex
only link at 10Mbps Half Duplex
Default Value: 0
media_type forces the line speed/duplex to the specified value in
megabits per second(Mbps). If this parameter is not specified or is set
to 0 and the link partner is set to auto-negotiate, the board will
auto-detect the correct speed.
int_mod_timer
Valid Range:
Default Value: 100
This value represents the minmum interval between interrupts controller
generated.
RxMemBlock
Valid Range:
Default Value: 64
This value is the number of receice memory block allocated by the driver.
Increasing this value allows the driver to buffer more incoming packets.
Each memory block is 1536 bytes.
NOTE: Depending on the available system resources, the request for a
higher number of receive descriptors may be denied. In this case,
use a lower number.
TxMemSize
Valid Range: 4-64
Default Value: 8
This value is the number KB of tranit memory allocated by the driver.
Increasing this value allows the driver to queue more tranits.
NOTE: Depending on the available system resources, the request for a
higher number of tranit descriptors may be denied. In this case,
use a lower number.
FlashVendor
Valid Range: 0-2
Default Value: 0
This value standards on vendor of spi flash used by the adapter.
0 for Atmel, 1 for SST, 2 for ST
Additional Configurations
=========================
Configuring the Driver on Different Distributions
Configuring a network driver to load properly when the system is started is
distribution dependent. Typically, the configuration process involves adding
an alias line to /etc/modules.conf as well as editing other system startup
scripts and/or configuration files. Many popular Linux distributions ship
with tools to make these changes for you. To learn the proper way to
configure a network device for your system, refer to your distribution
documentation. If during this process you are asked for the driver or module
name, the name for the Linux Base Driver for the Atheros AR8121/AR8113 is arl1e
As an example, if you install the arl1e driver for two AR8121/AR8113 adapters
(eth0 and eth1) and set the speed and duplex to 10full and 100half, add the
following to modules.conf:
alias eth0 arl1e
alias eth1 arl1e
options arl1e Speed=10,100 Duplex=2,1
Viewing Link Messages
Link messages will not be displayed to the console if the distribution is
restricting system messages. In order to see network driver link messages
on your console, set dmesg to eight by entering the following:
dmesg -n 8
NOTE: This setting is not saved across reboots.
Known Issues
============
NOTE: For distribution-specific information, see the ldistrib.txt file
included in the driver tar.
Driver Compilation
——
When trying to compile the driver by running make install, the following
error may occur:
“Linux kernel source not configured – missing version.h”
To solve this issue, create the version.h file by going to the Linux source
tree and entering:
make include/linux/version.h.
Support
=======
For general information, go to the Atheros support website at:
If an issue is identified with the released source code on the supported
kernel with a supported adapter, email the specific information related to
the issue to
License
=======
This software program is released under the terms of a license agreement
between you (‘Licensee’) and Atheros. Do not use or load this software or any
associated materials (collectively, the ‘Software’) until you have carefully
read the full terms and conditions of the LICENSE located in this software
package. By loading or using the Software, you agree to the terms of this
Agreement. If you do not agree with the terms of this Agreement, do not
install or use the Software.
* Other names and brands may be claimed as the property of others.
下载驱动，解压，然后进入驱动所在目录 运行make install
驱动就是内核模块。加载内核模块就是加载网卡驱动！
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