UM0851 datasheet(117/245 Pages) STMICROELECTRONICS

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UM0851

Communication device drivers

Doc ID 16604 Rev 2

117/245

/* append skb to Tx buffer ring */

......

if(Tx DMA not running) {

/* START Tx DMA */

......

}

return 0;

}

Attach protocols

channel_attach() is a function called by the generic HDLC layer when a certain protocol is

attached to the HDLC device. It requires the device to change the encoding schema and

CRC type based on the protocol. The function prototype is:

int

channel_xmit(struct net_device *dev,

unsigned short encoding,

unsigned short parity);

Note:

Currently, SPEAr HDLC driver does not support changing the encoding schema and CRC

type. So attach is left empty.

I/O control

channel_ioctl() is used to configure the HDLC channel. Most IOCTLs are handled in the

Linux network layer and the generic HDLC layer. This function just calls hdlc_ioctl to hand

over these IOCTL requests. Besides standard IOCTLs, the driver defines some private

IOCTLs which change the hardware behavior.

int channel_ioctl (struct net_device *dev, struct ifreq *ifr, int cmd) {

switch(cmd) {

case SIOCDEVPRIVATE:

......

break;

default:

return hdlc_ioctl(dev, ifr, cmd);

}

4.10.4

Driver parameters

TDM/E1 HDLC and RS485 HDLC share the same driver code. The differences between

them are specified in different driver parameters.

There are two kinds of driver parameters: one is for a physical port, another is for logical

channels (multiple logical channels may share the same physical port).

UM0851 Datasheet(PDF) 117 Page - STMicroelectronics

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