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awilliam
GitHub Repository: awilliam/linux-vfio
 Path: blob/master/arch/um/drivers/slip_common.h
10818 views
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#ifndef __UM_SLIP_COMMON_H

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#define __UM_SLIP_COMMON_H

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#define BUF_SIZE 1500

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 /* two bytes each for a (pathological) max packet of escaped chars +  *

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  * terminating END char + initial END char                            */

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#define ENC_BUF_SIZE (2 * BUF_SIZE + 2)

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/* SLIP protocol characters. */

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#define SLIP_END             0300	/* indicates end of frame	*/

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#define SLIP_ESC             0333	/* indicates byte stuffing	*/

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#define SLIP_ESC_END         0334	/* ESC ESC_END means END 'data'	*/

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#define SLIP_ESC_ESC         0335	/* ESC ESC_ESC means ESC 'data'	*/

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static inline int slip_unesc(unsigned char c, unsigned char *buf, int *pos,

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                             int *esc)

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{

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	int ret;

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	switch(c){

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	case SLIP_END:

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		*esc = 0;

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		ret=*pos;

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		*pos=0;

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		return(ret);

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	case SLIP_ESC:

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		*esc = 1;

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		return(0);

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	case SLIP_ESC_ESC:

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		if(*esc){

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			*esc = 0;

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			c = SLIP_ESC;

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		}

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		break;

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	case SLIP_ESC_END:

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		if(*esc){

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			*esc = 0;

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			c = SLIP_END;

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		}

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		break;

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	}

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	buf[(*pos)++] = c;

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	return(0);

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}

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static inline int slip_esc(unsigned char *s, unsigned char *d, int len)

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{

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	unsigned char *ptr = d;

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	unsigned char c;

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	/*

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	 * Send an initial END character to flush out any

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	 * data that may have accumulated in the receiver

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	 * due to line noise.

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	 */

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	*ptr++ = SLIP_END;

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	/*

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	 * For each byte in the packet, send the appropriate

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	 * character sequence, according to the SLIP protocol.

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	 */

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	while (len-- > 0) {

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		switch(c = *s++) {

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		case SLIP_END:

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			*ptr++ = SLIP_ESC;

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			*ptr++ = SLIP_ESC_END;

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			break;

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		case SLIP_ESC:

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			*ptr++ = SLIP_ESC;

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			*ptr++ = SLIP_ESC_ESC;

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			break;

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		default:

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			*ptr++ = c;

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			break;

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		}

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	}

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	*ptr++ = SLIP_END;

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	return (ptr - d);

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}

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struct slip_proto {

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	unsigned char ibuf[ENC_BUF_SIZE];

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	unsigned char obuf[ENC_BUF_SIZE];

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	int more; /* more data: do not read fd until ibuf has been drained */

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	int pos;

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	int esc;

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};

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static inline void slip_proto_init(struct slip_proto * slip)

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{

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	memset(slip->ibuf, 0, sizeof(slip->ibuf));

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	memset(slip->obuf, 0, sizeof(slip->obuf));

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	slip->more = 0;

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	slip->pos = 0;

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	slip->esc = 0;

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}

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extern int slip_proto_read(int fd, void *buf, int len,

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			   struct slip_proto *slip);

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extern int slip_proto_write(int fd, void *buf, int len,

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			    struct slip_proto *slip);

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#endif

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