Home > Device Driver > Linux Ethernet Driver Architecture

Linux Ethernet Driver Architecture


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. The usual way to receive a packet is through an interrupt, unless the interface is a purely software one like snull or the loopback interface. This is a range of addresses different from the normal memory address space. tr_setup function can be used to initialize token ring device fields. check over here

static int rtl8139_open(struct net_device *dev) { LOG_MSG("rtl8139_open is called\n"); return 0; } static int rtl8139_stop(struct net_device *dev) { LOG_MSG("rtl8139_open is called\n"); return 0; } static int rtl8139_start_xmit(struct sk_buff *skb, struct net_device For the interested reader, the definition of the structure may be found in . If that is case, we wrap it. Finally, the driver updates its statistics counter to record that a packet has been received.

Linux Ethernet Driver Architecture

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. The first part is executed in interrupt context and second part is executed in the bottom half ..Second part may interrupted by the first because interrupt context has the higher priority The declaration of device rtl8139 could done as follows struct net_device rtl8139 = {init: rtl8139_init}; The struct net_device structure is defined in include file linux/net_device.h .The code above initializes only The visible part of the structure is made up of the fields that can be explicitly assigned in static net_device structures.

Use this with care. College Thrissur. IFF_DEBUG This marks debug mode. Linux Ethernet Driver Source Code The driver presented in this article is minimal; it simply sends and receives packets and maintains some statistics.

netif_rx_schdule function first tests if poll needs to be scheduled using netif_rx_schedule_prep, is scheduled only if network interface up and next calls __netif_rx_schedule to schedule poll . skb­>protocol = eth_type_trans ( skb, dev); 9 Update statistics tp­>stats.rx_bytes += pkt_size; tp­>stats.rx_packets++; 10 Give the skb to kernel netif_receive_skb (skb); received ++; } /* end of while*/ tp­>cu_rx = cur_rx; int snull_release(struct net_device *dev) { /* release ports, irq and such -- like fops->close */ netif_stop_queue(dev); /* can't transmit any more */ MOD_DEC_USE_COUNT; return 0; } The function: void netif_stop_queue(struct net_device you could check here The second thing is to remap I/O addresses as explained in section above on Memory-Mapped I/O.

The same is true of the stop method; it just reverses the operations of open. Linux Ethernet Driver Info Controlling Transmission Concurrency The hard_start_xmit function is protected from concurrent calls by a spinlock (xmit_lock) in the net_device structure. A output of lsmod is also shown. (NB: You should be a super user in order to insert or delete a module.) [[email protected] modules]# insmod rtl8139.o Warning: loading test.o will taint Driver should fill some basic fundamenta l operations and can leave optional operations.

Writing A Network Device Driver Part 2 By Bhaskaran

The PC firmware initializes PCI hardware at system boot, mapping each devices I/O region to a different address, which is accessible from PCI configuration space, which consist of 256 bytes for http://gauss.ececs.uc.edu/Courses/e4022/code/drivers/Kernel/docs.html We will discuss functions rtl8139_open and rtl8139_stop, in this section. Linux Ethernet Driver Architecture You can write it by looking into the cleanup_module function defined below: void cleanup_module(void) { struct rtl8139_private *tp; tp = netdev_priv(rtl8139_dev); iounmap(tp->mmio_addr); pci_release_regions(tp->pci_dev); unregister_netdev(rtl8139_dev); pci_disable_device(tp->pci_dev); return; } Table 7: Function cleanup_module Network Device Driver Example Additionally, the kernel offers some generalized support for Ethernet devices, and there's no reason not to use it.

Now, we allocate memory, where outgoing packets reside before being sent on wire. check my blog Before the interface can carry packets, however, the kernel must open it and assign an address to it. Filling up of net_device structure: Kernel takes care of some ethernet defaults through a function (ether_setup()), which fills several fields in the net_devie structure. The kernel offers other interfaces to socket-buffer allocation, but they are not worth introducing here; socket buffers are explained in detail in "The Socket Buffers", later in this chapter. Writing Network Device Driver For Linux Pdf

There are other fields in struct net_device, but they are not used by network drivers. Way better than the unreliable 'dmesg|grep' (ring buffer...) –Dominik R Feb 10 '16 at 15:04 add a comment| up vote 2 down vote You can use the lsmod command to get Driver has to allocate a buffer and physical address of this is put in the buffer pointer . this content Note that for network devices, this structure is always put together at runtime.

struct rtl8139_private *tp = netdev_priv(dev); /* get registers base address in a local variable */ void __iomem *ioaddr = tp­>mmio_addr; 2.9 Registering Interrupt handler (ISR) Whenever a packet is received or Linux Ethernet Driver Download We will look at network devices, and the difference between memory-mapped I/O, port-mapped I/O, and PCI configuration space. It does not talk in depth specific to hardware, but what ever explained here is common to all network device drivers. 1.

Due to a historical accident, these are named byte, word, long, and quad accesses.

Later device reads packet contents from these addresses, DMA to its own FIFO, and transmits on wire. Compile and insert this again (you must unload earlier module using rmmod), and ping to another host. So, I need transfer data from kernel to Ethernet port. Linux Network Drive Also, you should avoid registering I/O ports and interrupt lines at this point.

This structure describes the characteristics of the found device. 3. Field tx_bufs is also used in same context, as we will see shortly. Infinitely long loaf of Bread How are banners kept upright? have a peek at these guys This function is explained below.

There is no "everything is a file" concept for network device (it means there is NO /dev/eth0 like file, similar to /dev/hda hard disk partition). Here, we call function rtl8139_hw_start to make the device ready for transmitting packets. A pointer to sk_buff is usually called skb, and we follow this practice both in the sample code and in the text. Later, we initialize MPC (Missed Packet Counter) register to zero and configure the device for not generating early interrupts.

It just requires a module in a standard manner, connecting the card hardware to actual software interface. ethernet belongs to network class. Once the device is reset, we enable transmission mode of the device by writing transmission enable value in CR. ifconfig eht0 up This brings up the ethernet card to listen to an IP address, a class-C client.

The following output was obtained on my system. the following function allocates interface descriptor block struct net_device. Hands Free - SaftyFirst "Request Access" hosted in Top Downloadsites HOWTO: Yoper 3.0 - a smart errorfixing Open source 3D Printing soon forlayman $ echo Sjef Bosman on Boot CDROM throughGRUBMisrocoft Although it is possible to write polling drivers, and a few exist in the official kernel, interrupt-driven operation is much better, both in terms of data throughput and computational demands.

This register lets us configure the interrupts; the device will be generating. Now, we allocate memory, where outgoing packets reside before being sent on wire. This driver is implemented in linux/drivers/net/8139too.c file. struct rtl8139_private definition can be found in 8139too.c file.

Some of the fields are used by ifconfig and netstat to provide the user with information about the current configuration. I have no idea from where to start ....kindly help. The constants PCI_VENDOR_ID_REALTEK, PCI_DEVICE_ID_REALTEK_8139 defines the vendorID and device_ID of the realtek card. If we know the address of ‘napi' field of struct rtl8139_private we can find the starting address of the struct rtl8139_private object using container_of function.

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. For these devices, the memcpy_toio, memcpy_fromio and memset_io functions are provided.