[PATCH] uml: slirp and slip driver cleanups and fixes

This patch merges a lot of duplicated code in the slip and slirp drivers,
abstracts out the slip protocol, and makes the slip driver work in 2.6.

Signed-off-by: Jeff Dike <jdike@addtoit.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

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