1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Greybus driver for the log protocol
4 *
5 * Copyright 2016 Google Inc.
6 */
7#include <linux/kernel.h>
8#include <linux/module.h>
9#include <linux/slab.h>
10#include <linux/sizes.h>
11#include <linux/uaccess.h>
12#include <linux/greybus.h>
13
14struct gb_log {
15	struct gb_connection *connection;
16};
17
18static int gb_log_request_handler(struct gb_operation *op)
19{
20	struct gb_connection *connection = op->connection;
21	struct device *dev = &connection->bundle->dev;
22	struct gb_log_send_log_request *receive;
23	u16 len;
24
25	if (op->type != GB_LOG_TYPE_SEND_LOG) {
26		dev_err(dev, "unknown request type 0x%02x\n", op->type);
27		return -EINVAL;
28	}
29
30	/* Verify size of payload */
31	if (op->request->payload_size < sizeof(*receive)) {
32		dev_err(dev, "log request too small (%zu < %zu)\n",
33			op->request->payload_size, sizeof(*receive));
34		return -EINVAL;
35	}
36	receive = op->request->payload;
37	len = le16_to_cpu(receive->len);
38	if (len != (op->request->payload_size - sizeof(*receive))) {
39		dev_err(dev, "log request wrong size %d vs %zu\n", len,
40			(op->request->payload_size - sizeof(*receive)));
41		return -EINVAL;
42	}
43	if (len == 0) {
44		dev_err(dev, "log request of 0 bytes?\n");
45		return -EINVAL;
46	}
47
48	if (len > GB_LOG_MAX_LEN) {
49		dev_err(dev, "log request too big: %d\n", len);
50		return -EINVAL;
51	}
52
53	/* Ensure the buffer is 0 terminated */
54	receive->msg[len - 1] = '\0';
55
56	/*
57	 * Print with dev_dbg() so that it can be easily turned off using
58	 * dynamic debugging (and prevent any DoS)
59	 */
60	dev_dbg(dev, "%s", receive->msg);
61
62	return 0;
63}
64
65static int gb_log_probe(struct gb_bundle *bundle,
66			const struct greybus_bundle_id *id)
67{
68	struct greybus_descriptor_cport *cport_desc;
69	struct gb_connection *connection;
70	struct gb_log *log;
71	int retval;
72
73	if (bundle->num_cports != 1)
74		return -ENODEV;
75
76	cport_desc = &bundle->cport_desc[0];
77	if (cport_desc->protocol_id != GREYBUS_PROTOCOL_LOG)
78		return -ENODEV;
79
80	log = kzalloc(sizeof(*log), GFP_KERNEL);
81	if (!log)
82		return -ENOMEM;
83
84	connection = gb_connection_create(bundle, le16_to_cpu(cport_desc->id),
85					  gb_log_request_handler);
86	if (IS_ERR(connection)) {
87		retval = PTR_ERR(connection);
88		goto error_free;
89	}
90
91	log->connection = connection;
92	greybus_set_drvdata(bundle, log);
93
94	retval = gb_connection_enable(connection);
95	if (retval)
96		goto error_connection_destroy;
97
98	return 0;
99
100error_connection_destroy:
101	gb_connection_destroy(connection);
102error_free:
103	kfree(log);
104	return retval;
105}
106
107static void gb_log_disconnect(struct gb_bundle *bundle)
108{
109	struct gb_log *log = greybus_get_drvdata(bundle);
110	struct gb_connection *connection = log->connection;
111
112	gb_connection_disable(connection);
113	gb_connection_destroy(connection);
114
115	kfree(log);
116}
117
118static const struct greybus_bundle_id gb_log_id_table[] = {
119	{ GREYBUS_DEVICE_CLASS(GREYBUS_CLASS_LOG) },
120	{ }
121};
122MODULE_DEVICE_TABLE(greybus, gb_log_id_table);
123
124static struct greybus_driver gb_log_driver = {
125	.name           = "log",
126	.probe          = gb_log_probe,
127	.disconnect     = gb_log_disconnect,
128	.id_table       = gb_log_id_table,
129};
130module_greybus_driver(gb_log_driver);
131
132MODULE_LICENSE("GPL v2");
133