1 files changed, 104 insertions, 0 deletions

diff --git a/arch/um/drivers/slip_common.h b/arch/um/drivers/slip_common.h
new file mode 100644
index 000000000000..2ae76d8f1be1
--- /dev/null
+++ b/arch/um/drivers/slip_common.h
@@ -0,0 +1,104 @@
+#ifndef __UM_SLIP_COMMON_H
+#define __UM_SLIP_COMMON_H
+
+#define BUF_SIZE 1500
+ /* two bytes each for a (pathological) max packet of escaped chars +  *
+  * terminating END char + initial END char                            */
+#define ENC_BUF_SIZE (2 * BUF_SIZE + 2)
+
+/* SLIP protocol characters. */
+#define SLIP_END             0300       /* indicates end of frame       */
+#define SLIP_ESC             0333       /* indicates byte stuffing      */
+#define SLIP_ESC_END         0334       /* ESC ESC_END means END 'data' */
+#define SLIP_ESC_ESC         0335       /* ESC ESC_ESC means ESC 'data' */
+
+static inline int slip_unesc(unsigned char c, unsigned char *buf, int *pos,
+                             int *esc)
+{
+        int ret;
+
+        switch(c){
+        case SLIP_END:
+                *esc = 0;
+                ret=*pos;
+                *pos=0;
+                return(ret);
+        case SLIP_ESC:
+                *esc = 1;
+                return(0);
+        case SLIP_ESC_ESC:
+                if(*esc){
+                        *esc = 0;
+                        c = SLIP_ESC;
+                }
+                break;
+        case SLIP_ESC_END:
+                if(*esc){
+                        *esc = 0;
+                        c = SLIP_END;
+                }
+                break;
+        }
+        buf[(*pos)++] = c;
+        return(0);
+}
+
+static inline int slip_esc(unsigned char *s, unsigned char *d, int len)
+{
+        unsigned char *ptr = d;
+        unsigned char c;
+
+        /*
+         * Send an initial END character to flush out any
+         * data that may have accumulated in the receiver
+         * due to line noise.
+         */
+
+        *ptr++ = SLIP_END;
+
+        /*
+         * For each byte in the packet, send the appropriate
+         * character sequence, according to the SLIP protocol.
+         */
+
+        while (len-- > 0) {
+                switch(c = *s++) {
+                case SLIP_END:
+                        *ptr++ = SLIP_ESC;
+                        *ptr++ = SLIP_ESC_END;
+                        break;
+                case SLIP_ESC:
+                        *ptr++ = SLIP_ESC;
+                        *ptr++ = SLIP_ESC_ESC;
+                        break;
+                default:
+                        *ptr++ = c;
+                        break;
+                }
+        }
+        *ptr++ = SLIP_END;
+        return (ptr - d);
+}
+
+struct slip_proto {
+        unsigned char ibuf[ENC_BUF_SIZE];
+        unsigned char obuf[ENC_BUF_SIZE];
+        int more; /* more data: do not read fd until ibuf has been drained */
+        int pos;
+        int esc;
+};
+
+#define SLIP_PROTO_INIT { \
+        .ibuf   = { '\0' }, \
+        .obuf   = { '\0' }, \
+        .more   = 0, \
+        .pos    = 0, \
+        .esc    = 0 \
+}
+
+extern int slip_proto_read(int fd, void *buf, int len,
+                           struct slip_proto *slip);
+extern int slip_proto_write(int fd, void *buf, int len,
+                            struct slip_proto *slip);
+
+#endif