The kernel turns it on when the interface is active and ready to transfer packets. In other words, packets sent through one of the interfaces should be received by the other, but the receiver of the outgoing packet shouldn’t be recognized as the local host. For example, a packet aimed at Because the real initialization is performed elsewhere, the initialization function has little to do, and a single statement does it:. We have just seen that the hardware header contains some information in addition to the destination address, the most important being the communication protocol. Hardware registration should be delayed until device open time; this is particularly important if interrupt lines are shared with other devices.
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The ifr pointer points to a kernel-space address that holds a copy of the structure passed by the user.
Packet reception, on the other hand, doesn’t need any special interrupt handling. The driver can change that state explicitly, however, with these functions:. We are now through discussing char and block drivers and are ready to move on to the fascinating world of networking.
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Such topics are not usually of concern to the driver writer, and it’s impossible to offer a satisfactory overview of networking technology in less than a few hundred pages. Most devices will be covered by one of these classes.
Add to Compare Shop for this product. The driver can hardwire a name for the interface or it can allow dynamic assignment, which works like this: The type of the name field in struct device was different. The field is not used by the kernel, like the memory fields linnux previously.
The single argument received by init is a pointer to the device being initialized; its return value is either 0 or a negative error code, usually -ENODEV. First of all, Linux 2. This functionality is obtained by assigning special hardware addresses to groups of lunux.
Downloads for Intel® 82574IT Gigabit Ethernet Controller
The network layer needs to have some information spelled out before it will be able to make sense of the packet. 825744it and shipping, etc. Both of these fields are meant to hold a jiffies value.
Then we need to specify how checksumming is to be performed or has been performed on the packet snull does not need to perform any checksums. Network interfaces are the third standard class of Linux devices, and this chapter lniux how they interact with the rest of the kernel. This is not an issue with snullwhich does all of its work using the CPU, so packet transmission is complete before the transmission function returns.
No real probing is performed for the snull interface, because it is not bound to any hardware. Packet sniffers such as tcpdump set promiscuous mode on the interface in order to retrieve all packets that travel on the kinux transmission medium.
By default, Ethernet interfaces use a hardware filter to ensure that they receive broadcast packets and packets directed to that interface’s hardware address only. Interaction between a network driver and the kernel proper deals with one network packet at a time; this allows protocol issues to be hidden neatly from the driver and the physical transmission to be hidden from the protocol. Lithography refers to the semiconductor technology used to manufacture an integrated circuit, and is reported in nanometer nmindicative of the size of features built on the semiconductor.
Intel® 82574IT Gigabit Ethernet Controller
On 882574it local area network it achieves clock accuracy in the sub-microsecond range, making it suitable for measurement and control systems. We’ll see the multicast flags used in “Multicasting” later in this chapter. We are not going to describe the whole structure here, just the fields that might be used from within a driver.
As soon as the function returns, however, it may be called again. Since there is no equivalent of major and minor numbers for network interfaces, a network driver does not request such a number. The following function is a typical implementation of the function in a full-featured ff driver.
Since the “remote” systems simulated by snull do not really exist, there is nobody available to answer ARP requests for them. The name of the device.
The transmission function thus performs only some sanity checks on the packet and transmits the data through the hardware-related function. The real work needed to return meaningful statistics is distributed throughout the driver, where the various fields are updated.
Linux Device Drivers, 2nd Edition: Chapter Network Drivers
Fundamental methods include those that are needed to be able to use the interface; optional methods implement more advanced functionalities that are not strictly required. The usual interrupt routine can tell the difference between a new-packet-arrived interrupt and a done-transmitting notification by checking a status register found on the physical device.
The interface interrupts the processor to signal one of two possible events: