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The RealTek interface Introduction to the RTL-8139 network controller registers.

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Presentation on theme: "The RealTek interface Introduction to the RTL-8139 network controller registers."— Presentation transcript:

1 The RealTek interface Introduction to the RTL-8139 network controller registers

2 Device driver’s duties Summary of device-driver responsibilities: –Detect –Register –Reset –Allocate –Initialize –Enable –Configure –Manage

3 PCI device detection #include #define VID0x10EC // RealTek Corp #define DID0x8139// RTL8139 chip struct pci_dev *devp;// structure pointer devp = pci_find_device( VID, DID, NULL ); if ( devp == NULL ) return –ENODEV;

4 Two access methods The 8139 provides two ways for drivers to access its device-registers: –via io-port addresses (use ‘in’ and ‘out’) –via memory addresses (use ‘mov’, ‘and’, ‘or’) io_base = pci_resource_start( devp, 0 ); io_len = pci_resource_len( devp, 0 ); membase = pci_resource_start( devp, 1 ); memlen = pci_resource_len( devp, 1 );

5 Advantages/Disadvantages Memory-space access is faster and more flexible (can directly use x86 instructions) But memory-mapped access requires the setup of suitable entries in the system’s page-directory and page-table(s), and the driver-writer must consider caching issues and instruction-reordering by the compiler I/O port-access is more straightforward

6 How many registers? By either access-method, the RTL-8139 provides 256-byte programming interface Register-sizes vary: 8-bit, 16-bit, 32-bit Register-implementations vary: most are read/write; some are read-only, some are write-only; some are ‘reserved’; some may have undisclosed functions; some have clearly documented ‘side-effects’

7 You need these Manuals! RealTek has two official publications that are vital for writers of device-drivers: –RTL-8139D(L) Datasheet (60 pages) –RTL-8100 Programming Guide (10 pages) These docs are not protected by copyright, so we are providing copies for you to use

8 The Linux driver You can also look at the source-code for the Linux driver that operates our NICs: –See: ‘/usr/src/linux/drivers/net/8139too.c’ And there are other public-domain drivers for the 8139 controller as well The authors of these drivers have added comments in their code, which may help whenever the manuals are ambiguous

9 Examination at ‘runtime’ It is very helpful to look at the contents of the RTL-8139 registers while the network is being used (as programmed by another driver-writer) We have created a special device-driver that makes this possible: ‘mmap8139.c’ Using this driver, a companion program (‘nicregs.cpp’) displays all 8139 registers

10 Command Register byte-register at offset 0x37: 000ResetTxEn0 RxBuf empty 7 6 5 4 3 2 1 0 r / or / w RxEn Legend: RxBuf empty (Receive Buffer is Empty): 1 = yes. 0 = no TxEn (Transmission is Enabled): 1 = yes, 0 = no RxEn (Reception is Enabled): 1 = yes, 0 – no Reset (Resets the controller): writing 0 to this bit has no effect; writing 1 to this bit initiates a ‘reset’ operation, placing all the NIC registers and internal buffers into a known default state; this bit automatically clears upon completion of the reset operation.

11 The six ID registers Six byte-registers (at offsets 0x00-0x05) hold the unique identification number of your network controller – known as the MAC address (Media Access Control) The transceiver uses the MAC-address to ‘filter out’ all packets on the local network that were not directed to your machine These six registers get initialized during power-on reset (and seem to be read-only)

12 Display of the MAC-address Here’s a programming loop that will print your MAC-address using the customary hexadecimal format: xx:xx:xx:xx:xx:xx unsigned char *reg = ; for (int i = 0; i < 6; i++) { char ch = ( i < 5 ) ? ‘:’ : ‘ ‘; printf( “%02X%c”, reg[ i ], ch ); }

13 Transmit Configuration 32-bit register (offsets 0x40-0x43): Hardware Version ID (Part A) Inter Frame Gap HWVER ID (Part B) GAP 2 LOOP BACK TEST CRCCRC MAX DMA BURST Transmission Retry Count CLR ABT 31 30 26 25 24 23 22 21 20 19 18 17 16 15 11 10 8 7 4 0

14 Receive Configuration 32-bit register (offsets 0x44-0x47) reserved Early Receive Threshold reserved Mult ER INT Rx ERR 8 Rx FIFO Threshold Rx Buf Length Max DMA Burse Size WRAPWRAP 0 LONGLONG RUNTRUNT BCASTBCAST MCASTMCAST MACMAC ALLALL 31 28 27 24 23 18 17 16 15 13 12 11 10 8 7 5 4 3 2 1 0

15 In-class exercise #1 Enhance the information displayed by the ‘nicregs.cpp’ demo-program by showing the workstation’s hostname: #include char hostname[ 64 ]; gethostname( hostname, 64 ); printf( “station is %s \n”, hostname );

16 In-class exercise #2 Enhance the ‘nicregs.cpp’ application, by adding ‘printf()’ statements to display the information in registers in a way that can more easily understood by humans: –Show the chip’s unique MAC address –Show the Transmit Configuration fields –Show the Receive Configuration fields –Show the Command Register settings

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