1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Copyright (C) ST-Ericsson AB 2010
4 * Author:	Sjur Brendeland
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
34void cfserl_release(struct cflayer *layer)
35{
36	kfree(layer);
37}
38
39struct cflayer *cfserl_create(int instance, bool use_stx)
40{
41	struct cfserl *this = kzalloc(sizeof(struct cfserl), GFP_ATOMIC);
42	if (!this)
43		return NULL;
44	caif_assert(offsetof(struct cfserl, layer) == 0);
45	this->layer.receive = cfserl_receive;
46	this->layer.transmit = cfserl_transmit;
47	this->layer.ctrlcmd = cfserl_ctrlcmd;
48	this->usestx = use_stx;
49	spin_lock_init(&this->sync);
50	snprintf(this->layer.name, CAIF_LAYER_NAME_SZ, "ser1");
51	return &this->layer;
52}
53
54static int cfserl_receive(struct cflayer *l, struct cfpkt *newpkt)
55{
56	struct cfserl *layr = container_obj(l);
57	u16 pkt_len;
58	struct cfpkt *pkt = NULL;
59	struct cfpkt *tail_pkt = NULL;
60	u8 tmp8;
61	u16 tmp;
62	u8 stx = CFSERL_STX;
63	int ret;
64	u16 expectlen = 0;
65
66	caif_assert(newpkt != NULL);
67	spin_lock(&layr->sync);
68
69	if (layr->incomplete_frm != NULL) {
70		layr->incomplete_frm =
71		    cfpkt_append(layr->incomplete_frm, newpkt, expectlen);
72		pkt = layr->incomplete_frm;
73		if (pkt == NULL) {
74			spin_unlock(&layr->sync);
75			return -ENOMEM;
76		}
77	} else {
78		pkt = newpkt;
79	}
80	layr->incomplete_frm = NULL;
81
82	do {
83		/* Search for STX at start of pkt if STX is used */
84		if (layr->usestx) {
85			cfpkt_extr_head(pkt, &tmp8, 1);
86			if (tmp8 != CFSERL_STX) {
87				while (cfpkt_more(pkt)
88				       && tmp8 != CFSERL_STX) {
89					cfpkt_extr_head(pkt, &tmp8, 1);
90				}
91				if (!cfpkt_more(pkt)) {
92					cfpkt_destroy(pkt);
93					layr->incomplete_frm = NULL;
94					spin_unlock(&layr->sync);
95					return -EPROTO;
96				}
97			}
98		}
99
100		pkt_len = cfpkt_getlen(pkt);
101
102		/*
103		 *  pkt_len is the accumulated length of the packet data
104		 *  we have received so far.
105		 *  Exit if frame doesn't hold length.
106		 */
107
108		if (pkt_len < 2) {
109			if (layr->usestx)
110				cfpkt_add_head(pkt, &stx, 1);
111			layr->incomplete_frm = pkt;
112			spin_unlock(&layr->sync);
113			return 0;
114		}
115
116		/*
117		 *  Find length of frame.
118		 *  expectlen is the length we need for a full frame.
119		 */
120		cfpkt_peek_head(pkt, &tmp, 2);
121		expectlen = le16_to_cpu(tmp) + 2;
122		/*
123		 * Frame error handling
124		 */
125		if (expectlen < SERIAL_MINIUM_PACKET_SIZE
126		    || expectlen > SERIAL_MAX_FRAMESIZE) {
127			if (!layr->usestx) {
128				if (pkt != NULL)
129					cfpkt_destroy(pkt);
130				layr->incomplete_frm = NULL;
131				spin_unlock(&layr->sync);
132				return -EPROTO;
133			}
134			continue;
135		}
136
137		if (pkt_len < expectlen) {
138			/* Too little received data */
139			if (layr->usestx)
140				cfpkt_add_head(pkt, &stx, 1);
141			layr->incomplete_frm = pkt;
142			spin_unlock(&layr->sync);
143			return 0;
144		}
145
146		/*
147		 * Enough data for at least one frame.
148		 * Split the frame, if too long
149		 */
150		if (pkt_len > expectlen)
151			tail_pkt = cfpkt_split(pkt, expectlen);
152		else
153			tail_pkt = NULL;
154
155		/* Send the first part of packet upwards.*/
156		spin_unlock(&layr->sync);
157		ret = layr->layer.up->receive(layr->layer.up, pkt);
158		spin_lock(&layr->sync);
159		if (ret == -EILSEQ) {
160			if (layr->usestx) {
161				if (tail_pkt != NULL)
162					pkt = cfpkt_append(pkt, tail_pkt, 0);
163				/* Start search for next STX if frame failed */
164				continue;
165			} else {
166				cfpkt_destroy(pkt);
167				pkt = NULL;
168			}
169		}
170
171		pkt = tail_pkt;
172
173	} while (pkt != NULL);
174
175	spin_unlock(&layr->sync);
176	return 0;
177}
178
179static int cfserl_transmit(struct cflayer *layer, struct cfpkt *newpkt)
180{
181	struct cfserl *layr = container_obj(layer);
182	u8 tmp8 = CFSERL_STX;
183	if (layr->usestx)
184		cfpkt_add_head(newpkt, &tmp8, 1);
185	return layer->dn->transmit(layer->dn, newpkt);
186}
187
188static void cfserl_ctrlcmd(struct cflayer *layr, enum caif_ctrlcmd ctrl,
189			   int phyid)
190{
191	layr->up->ctrlcmd(layr->up, ctrl, phyid);
192}
193