LXR linux/arch/um/drivers/slip

   1/* SPDX-License-Identifier: GPL-2.0 */
   2#ifndef __UM_SLIP_COMMON_H
   3#define __UM_SLIP_COMMON_H
   4
   5#define BUF_SIZE 1500
   6 /* two bytes each for a (pathological) max packet of escaped chars +  *
   7  * terminating END char + initial END char                            */
   8#define ENC_BUF_SIZE (2 * BUF_SIZE + 2)
   9
  10/* SLIP protocol characters. */
  11#define SLIP_END             0300       /* indicates end of frame       */
  12#define SLIP_ESC             0333       /* indicates byte stuffing      */
  13#define SLIP_ESC_END         0334       /* ESC ESC_END means END 'data' */
  14#define SLIP_ESC_ESC         0335       /* ESC ESC_ESC means ESC 'data' */
  15
  16static inline int slip_unesc(unsigned char c, unsigned char *buf, int *pos,
  17                             int *esc)
  18{
  19        int ret;
  20
  21        switch(c){
  22        case SLIP_END:
  23                *esc = 0;
  24                ret=*pos;
  25                *pos=0;
  26                return(ret);
  27        case SLIP_ESC:
  28                *esc = 1;
  29                return(0);
  30        case SLIP_ESC_ESC:
  31                if(*esc){
  32                        *esc = 0;
  33                        c = SLIP_ESC;
  34                }
  35                break;
  36        case SLIP_ESC_END:
  37                if(*esc){
  38                        *esc = 0;
  39                        c = SLIP_END;
  40                }
  41                break;
  42        }
  43        buf[(*pos)++] = c;
  44        return(0);
  45}
  46
  47static inline int slip_esc(unsigned char *s, unsigned char *d, int len)
  48{
  49        unsigned char *ptr = d;
  50        unsigned char c;
  51
  52        /*
  53         * Send an initial END character to flush out any
  54         * data that may have accumulated in the receiver
  55         * due to line noise.
  56         */
  57
  58        *ptr++ = SLIP_END;
  59
  60        /*
  61         * For each byte in the packet, send the appropriate
  62         * character sequence, according to the SLIP protocol.
  63         */
  64
  65        while (len-- > 0) {
  66                switch(c = *s++) {
  67                case SLIP_END:
  68                        *ptr++ = SLIP_ESC;
  69                        *ptr++ = SLIP_ESC_END;
  70                        break;
  71                case SLIP_ESC:
  72                        *ptr++ = SLIP_ESC;
  73                        *ptr++ = SLIP_ESC_ESC;
  74                        break;
  75                default:
  76                        *ptr++ = c;
  77                        break;
  78                }
  79        }
  80        *ptr++ = SLIP_END;
  81        return (ptr - d);
  82}
  83
  84struct slip_proto {
  85        unsigned char ibuf[ENC_BUF_SIZE];
  86        unsigned char obuf[ENC_BUF_SIZE];
  87        int more; /* more data: do not read fd until ibuf has been drained */
  88        int pos;
  89        int esc;
  90};
  91
  92static inline void slip_proto_init(struct slip_proto * slip)
  93{
  94        memset(slip->ibuf, 0, sizeof(slip->ibuf));
  95        memset(slip->obuf, 0, sizeof(slip->obuf));
  96        slip->more = 0;
  97        slip->pos = 0;
  98        slip->esc = 0;
  99}
 100
 101extern int slip_proto_read(int fd, void *buf, int len,
 102                           struct slip_proto *slip);
 103extern int slip_proto_write(int fd, void *buf, int len,
 104                            struct slip_proto *slip);
 105
 106#endif
 107