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Network Device Driver In Linux

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The first argument of the function is a pointer to structure sk_buff. If you read the RealTek8139 specification, the section "Register Description" has TSAD0, TSAD1, TSAD2 and TSAD3 registers at offset 0x20, 0x24, 0x28, 0x2C, respectively. Copyright © 2003, Bhaskaran. The next function, barrier ( ), is called to force the kernel to do required memory I/O immediately without doing any optimization. Check This Out

Any further demultiplexing of interrupts is the interrupt handler's job. The reference to the device object is released. Space.c declares a linked list of all the network devices, both driver-specific structures like plip1 and general-purpose eth devices. void fc_setup(struct net_device *dev); Initializes for fiber channel devices.

Linux Ethernet Driver Example

The assignment to hard_header_cache is there for a similar reason: it disables the caching of the (nonexistent) ARP replies on this interface. probe function receives two parameters. This way of setting up drivers permits incremental assignment of devices to the names eth0, eth1, and so on, without changing the name field of each device. These are defined in linux/pci.h.

Networking Basics One could set his/her PC for networking through netconfig command. First is to reserve the above resources (memory space) by driver; this is done by calling the function pci_request_regions. It is mostly present for BSD compatibility; the kernel makes little use of it. Linux Ethernet Driver Source Code These functions are inb, inw, inl, outb, outw and outl.

At this time, the device is ready to send packets, but the function to send packets out is missing. (Remember hard_start_xmit.) So, let's do it. Linux Ethernet Driver Architecture This is a consequence of the internal workings of the interface -- snull has to look inside and interpret the packets to properly emulate a pair of hardware interfaces. RTL8139_ProgrammersGuide.pdf explains how the reception and transmission happen in Realtek 8139 chip where as RTL8139D_DataSheet.pdf explains register's details. i thought about this It is strongly recommended to have Rubini's Linux Device Drivers book with you for quick API reference.

This function does not return until any executing interrupts for this IRQ have completed. Linux Ethernet Driver Download Now, we allocate memory, where outgoing packets reside before being sent on wire. Therefore, we allocate 2048 bytes of buffer extra to cope up with such situations. This chapter describes how the network interfaces fit in with the rest of the Linux kernel and shows a memory-based modularized network interface, which is called (you guessed it) snull.

  1. Instead of having the device asynchronously notify the driver about frame receptions, the driver instructs the device to generate an interrupt at regular intervals.
  2. dev_addr - Hardware address (Ethernet address or MAC address) broadcast - device broadcast address.
  3. The struct pci_dev holds the pci interface and other holds the network interface respectively, which has been mentioned earlier.
  4. As you know, any device can be interfaced with CPU using any bus like PCI , USB, Firewire etc .
  5. This MAC address is stored in the ‘dev_addr' and ‘perm_addr' fields of net_device object.
  6. Both tx_buf and tx_bufs do hold kernel virtual address, which can be used by the driver, but the device cannot use these addresses.
  7. If resources are reserved, another driver cannot use these resources.

Linux Ethernet Driver Architecture

If the name contains a %d format string, the first available device name with the given base is used; assigned numbers start at zero. The snull software interface assigns it from within open; it just fakes a hardware number using an ASCII string of length ETH_ALEN, the length of Ethernet hardware addresses. Linux Ethernet Driver Example Once the packet is sent network interface card raises an interrupt and writes status of the interrupt in its status registers. Writing A Network Device Driver Part 2 By Bhaskaran Making Device Ready to Receive Packets Now, we will make the device ready to receive packets.

snull has a template for the function if you are interested. http://pic3nter.com/linux-ethernet/network-device-drivers-in-linux.php One for memory mapped ,one for port mapped and etc .For each base address an object of type struct resource is created and filled with base address ,size and flags . This macro takes two parameters , one is pci_dev object of the device that you want base address and another is base address register number. Some variants are provided for these functions. Writing Network Device Driver For Linux Pdf

This field is used by the network layer to drive packet transmission. Hardware registration should be delayed until device open time; this is particularly important if interrupt lines are shared with other devices. An author of the driver must issue a read from the same device to ensure that writes have occurred in the manner the author wanted it. this contact form Photoshop: how to draw a moon-like shape Why didn't Harry play king?

These registers store "Transmit Start Address of Descriptors" i.e., they store starting address (in memory) of packets to be transmitted. Linux Network Drive The driver should make no changes to these fields. For an quick overview of the kernel data structures, functions, the interactions between driver and upper layer of protocol stack, we first attempt to develop a hardware independent driver.

static struct pci_dev* probe_for_realtek8139(void) { struct pci_dev *pdev = NULL; /* Ensure we are not working on a non-PCI system * if(!pci_present( )) { LOG_MSG("<1>pci not present\n"); return pdev; } #define

The field is used in "Initializing Each Device", later in this chapter. Driver has to take the packet from the RxRing , copy that into sk_buff object and give it to the kernel. Here is a list of register offsets, used in code. Linux Net_device Network interface card also can be interfaced with CPU using any of the above said buses .

void tr_configure(struct net_device *dev); Handles setup for token ring network interfaces. Packet reception, on the other hand, doesn't need any special interrupt handling. Later device reads packet contents from these addresses, DMA to its own FIFO, and transmits on wire. navigate here struct rtl8139_private { struct pci_dev *pci_dev; /* PCI device */ void *mmio_addr; /* memory mapped I/O addr */ unsigned long regs_len; /* length of I/O or MMI/O region */ }; Table

After sending the packet network interface card will raise an interrupt. The rmem fields are never referenced outside of the driver itself. Although this article does not require detailed knowledge about sk_buff's structure, its details can be found at http://www.tldp.org/LDP/khg/HyperNews/get/net/net-intro.html. rc = pci_request_regions (pdev, DRV_NAME); if (rc) goto err_out; Some PCI devices have the capability of bus mastering .

Next, we configure TCR (Transmission Configuration Register). This code would be written in initialization routine of the driver module. Once again, the sample code works on the 2.0 and 2.2 kernels as well, and we cover the differences between those kernels and 2.4 at the end of the chapter. For example, a packet aimed at 192.168.0.32 will leave through sn0 and reappear at sn1 with a destination address of 192.168.1.32, which is not a local address for the host computer.