1/*
2 * Copyright (C) ST-Ericsson AB 2010
3 * Author:	Sjur Brendeland
4 * License terms: GNU General Public License (GPL) version 2
5 */
6
7#define pr_fmt(fmt) KBUILD_MODNAME ":%s(): " fmt, __func__
8
9#include <linux/stddef.h>
10#include <linux/spinlock.h>
11#include <linux/slab.h>
12#include <net/caif/caif_layer.h>
13#include <net/caif/cfpkt.h>
14#include <net/caif/cfserl.h>
15
16#define container_obj(layr) ((struct cfserl *) layr)
17
18#define CFSERL_STX 0x02
19#define SERIAL_MINIUM_PACKET_SIZE 4
20#define SERIAL_MAX_FRAMESIZE 4096
21struct cfserl {
22	struct cflayer layer;
23	struct cfpkt *incomplete_frm;
24	/* Protects parallel processing of incoming packets */
25	spinlock_t sync;
26	bool usestx;
27};
28
29static int cfserl_receive(struct cflayer *layr, struct cfpkt *pkt);
30static int cfserl_transmit(struct cflayer *layr, struct cfpkt *pkt);
31static void cfserl_ctrlcmd(struct cflayer *layr, enum caif_ctrlcmd ctrl,
32			   int phyid);
33
34struct cflayer *cfserl_create(int instance, bool use_stx)
35{
36	struct cfserl *this = kzalloc(sizeof(struct cfserl), GFP_ATOMIC);
37	if (!this)
38		return NULL;
39	caif_assert(offsetof(struct cfserl, layer) == 0);
40	this->layer.receive = cfserl_receive;
41	this->layer.transmit = cfserl_transmit;
42	this->layer.ctrlcmd = cfserl_ctrlcmd;
43	this->usestx = use_stx;
44	spin_lock_init(&this->sync);
45	snprintf(this->layer.name, CAIF_LAYER_NAME_SZ, "ser1");
46	return &this->layer;
47}
48
49static int cfserl_receive(struct cflayer *l, struct cfpkt *newpkt)
50{
51	struct cfserl *layr = container_obj(l);
52	u16 pkt_len;
53	struct cfpkt *pkt = NULL;
54	struct cfpkt *tail_pkt = NULL;
55	u8 tmp8;
56	u16 tmp;
57	u8 stx = CFSERL_STX;
58	int ret;
59	u16 expectlen = 0;
60
61	caif_assert(newpkt != NULL);
62	spin_lock(&layr->sync);
63
64	if (layr->incomplete_frm != NULL) {
65		layr->incomplete_frm =
66		    cfpkt_append(layr->incomplete_frm, newpkt, expectlen);
67		pkt = layr->incomplete_frm;
68		if (pkt == NULL) {
69			spin_unlock(&layr->sync);
70			return -ENOMEM;
71		}
72	} else {
73		pkt = newpkt;
74	}
75	layr->incomplete_frm = NULL;
76
77	do {
78		/* Search for STX at start of pkt if STX is used */
79		if (layr->usestx) {
80			cfpkt_extr_head(pkt, &tmp8, 1);
81			if (tmp8 != CFSERL_STX) {
82				while (cfpkt_more(pkt)
83				       && tmp8 != CFSERL_STX) {
84					cfpkt_extr_head(pkt, &tmp8, 1);
85				}
86				if (!cfpkt_more(pkt)) {
87					cfpkt_destroy(pkt);
88					layr->incomplete_frm = NULL;
89					spin_unlock(&layr->sync);
90					return -EPROTO;
91				}
92			}
93		}
94
95		pkt_len = cfpkt_getlen(pkt);
96
97		/*
98		 *  pkt_len is the accumulated length of the packet data
99		 *  we have received so far.
100		 *  Exit if frame doesn't hold length.
101		 */
102
103		if (pkt_len < 2) {
104			if (layr->usestx)
105				cfpkt_add_head(pkt, &stx, 1);
106			layr->incomplete_frm = pkt;
107			spin_unlock(&layr->sync);
108			return 0;
109		}
110
111		/*
112		 *  Find length of frame.
113		 *  expectlen is the length we need for a full frame.
114		 */
115		cfpkt_peek_head(pkt, &tmp, 2);
116		expectlen = le16_to_cpu(tmp) + 2;
117		/*
118		 * Frame error handling
119		 */
120		if (expectlen < SERIAL_MINIUM_PACKET_SIZE
121		    || expectlen > SERIAL_MAX_FRAMESIZE) {
122			if (!layr->usestx) {
123				if (pkt != NULL)
124					cfpkt_destroy(pkt);
125				layr->incomplete_frm = NULL;
126				expectlen = 0;
127				spin_unlock(&layr->sync);
128				return -EPROTO;
129			}
130			continue;
131		}
132
133		if (pkt_len < expectlen) {
134			/* Too little received data */
135			if (layr->usestx)
136				cfpkt_add_head(pkt, &stx, 1);
137			layr->incomplete_frm = pkt;
138			spin_unlock(&layr->sync);
139			return 0;
140		}
141
142		/*
143		 * Enough data for at least one frame.
144		 * Split the frame, if too long
145		 */
146		if (pkt_len > expectlen)
147			tail_pkt = cfpkt_split(pkt, expectlen);
148		else
149			tail_pkt = NULL;
150
151		/* Send the first part of packet upwards.*/
152		spin_unlock(&layr->sync);
153		ret = layr->layer.up->receive(layr->layer.up, pkt);
154		spin_lock(&layr->sync);
155		if (ret == -EILSEQ) {
156			if (layr->usestx) {
157				if (tail_pkt != NULL)
158					pkt = cfpkt_append(pkt, tail_pkt, 0);
159				/* Start search for next STX if frame failed */
160				continue;
161			} else {
162				cfpkt_destroy(pkt);
163				pkt = NULL;
164			}
165		}
166
167		pkt = tail_pkt;
168
169	} while (pkt != NULL);
170
171	spin_unlock(&layr->sync);
172	return 0;
173}
174
175static int cfserl_transmit(struct cflayer *layer, struct cfpkt *newpkt)
176{
177	struct cfserl *layr = container_obj(layer);
178	u8 tmp8 = CFSERL_STX;
179	if (layr->usestx)
180		cfpkt_add_head(newpkt, &tmp8, 1);
181	return layer->dn->transmit(layer->dn, newpkt);
182}
183
184static void cfserl_ctrlcmd(struct cflayer *layr, enum caif_ctrlcmd ctrl,
185			   int phyid)
186{
187	layr->up->ctrlcmd(layr->up, ctrl, phyid);
188}
189