1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * debugfs attributes for Wilco EC
4  *
5  * Copyright 2019 Google LLC
6  *
7  * There is only one attribute used for debugging, called raw.
8  * You can write a hexadecimal sentence to raw, and that series of bytes
9  * will be sent to the EC. Then, you can read the bytes of response
10  * by reading from raw.
11  *
12  * For writing:
13  * Bytes 0-1 indicate the message type:
14  *         00 F0 = Execute Legacy Command
15  *         00 F2 = Read/Write NVRAM Property
16  * Byte 2 provides the command code
17  * Bytes 3+ consist of the data passed in the request
18  *
19  * When referencing the EC interface spec, byte 2 corresponds to MBOX[0],
20  * byte 3 corresponds to MBOX[1], etc.
21  *
22  * At least three bytes are required, for the msg type and command,
23  * with additional bytes optional for additional data.
24  *
25  * Example:
26  * // Request EC info type 3 (EC firmware build date)
27  * $ echo 00 f0 38 00 03 00 > raw
28  * // View the result. The decoded ASCII result "12/21/18" is
29  * // included after the raw hex.
30  * $ cat raw
31  * 00 31 32 2f 32 31 2f 31 38 00 38 00 01 00 2f 00  .12/21/18.8...
32  */
33 
34 #include <linux/ctype.h>
35 #include <linux/debugfs.h>
36 #include <linux/fs.h>
37 #include <linux/module.h>
38 #include <linux/platform_data/wilco-ec.h>
39 #include <linux/platform_device.h>
40 
41 #define DRV_NAME "wilco-ec-debugfs"
42 
43 /* The 256 raw bytes will take up more space when represented as a hex string */
44 #define FORMATTED_BUFFER_SIZE (EC_MAILBOX_DATA_SIZE_EXTENDED * 4)
45 
46 struct wilco_ec_debugfs {
47 	struct wilco_ec_device *ec;
48 	struct dentry *dir;
49 	size_t response_size;
50 	u8 raw_data[EC_MAILBOX_DATA_SIZE_EXTENDED];
51 	u8 formatted_data[FORMATTED_BUFFER_SIZE];
52 };
53 static struct wilco_ec_debugfs *debug_info;
54 
55 /**
56  * parse_hex_sentence() - Convert a ascii hex representation into byte array.
57  * @in: Input buffer of ascii.
58  * @isize: Length of input buffer.
59  * @out: Output buffer.
60  * @osize: Length of output buffer, e.g. max number of bytes to parse.
61  *
62  * An valid input is a series of ascii hexadecimal numbers, separated by spaces.
63  * An example valid input is
64  * "   00 f2 0    000076 6 0  ff"
65  *
66  * If an individual "word" within the hex sentence is longer than MAX_WORD_SIZE,
67  * then the sentence is illegal, and parsing will fail.
68  *
69  * Return: Number of bytes parsed, or negative error code on failure.
70  */
71 static int parse_hex_sentence(const char *in, int isize, u8 *out, int osize)
72 {
73 	int n_parsed = 0;
74 	int word_start = 0;
75 	int word_end;
76 	int word_len;
77 	/* Temp buffer for holding a "word" of chars that represents one byte */
78 	#define MAX_WORD_SIZE 16
79 	char tmp[MAX_WORD_SIZE + 1];
80 	u8 byte;
81 
82 	while (word_start < isize && n_parsed < osize) {
83 		/* Find the start of the next word */
84 		while (word_start < isize && isspace(in[word_start]))
85 			word_start++;
86 		 /* reached the end of the input before next word? */
87 		if (word_start >= isize)
88 			break;
89 
90 		/* Find the end of this word */
91 		word_end = word_start;
92 		while (word_end < isize && !isspace(in[word_end]))
93 			word_end++;
94 
95 		/* Copy to a tmp NULL terminated string */
96 		word_len = word_end - word_start;
97 		if (word_len > MAX_WORD_SIZE)
98 			return -EINVAL;
99 		memcpy(tmp, in + word_start, word_len);
100 		tmp[word_len] = '\0';
101 
102 		/*
103 		 * Convert from hex string, place in output. If fails to parse,
104 		 * just return -EINVAL because specific error code is only
105 		 * relevant for this one word, returning it would be confusing.
106 		 */
107 		if (kstrtou8(tmp, 16, &byte))
108 			return -EINVAL;
109 		out[n_parsed++] = byte;
110 
111 		word_start = word_end;
112 	}
113 	return n_parsed;
114 }
115 
116 /* The message type takes up two bytes*/
117 #define TYPE_AND_DATA_SIZE ((EC_MAILBOX_DATA_SIZE) + 2)
118 
119 static ssize_t raw_write(struct file *file, const char __user *user_buf,
120 			 size_t count, loff_t *ppos)
121 {
122 	char *buf = debug_info->formatted_data;
123 	struct wilco_ec_message msg;
124 	u8 request_data[TYPE_AND_DATA_SIZE];
125 	ssize_t kcount;
126 	int ret;
127 
128 	if (count > FORMATTED_BUFFER_SIZE)
129 		return -EINVAL;
130 
131 	kcount = simple_write_to_buffer(buf, FORMATTED_BUFFER_SIZE, ppos,
132 					user_buf, count);
133 	if (kcount < 0)
134 		return kcount;
135 
136 	ret = parse_hex_sentence(buf, kcount, request_data, TYPE_AND_DATA_SIZE);
137 	if (ret < 0)
138 		return ret;
139 	/* Need at least two bytes for message type and one for command */
140 	if (ret < 3)
141 		return -EINVAL;
142 
143 	/* Clear response data buffer */
144 	memset(debug_info->raw_data, '\0', EC_MAILBOX_DATA_SIZE_EXTENDED);
145 
146 	msg.type = request_data[0] << 8 | request_data[1];
147 	msg.flags = WILCO_EC_FLAG_RAW;
148 	msg.command = request_data[2];
149 	msg.request_data = ret > 3 ? request_data + 3 : 0;
150 	msg.request_size = ret - 3;
151 	msg.response_data = debug_info->raw_data;
152 	msg.response_size = EC_MAILBOX_DATA_SIZE;
153 
154 	/* Telemetry commands use extended response data */
155 	if (msg.type == WILCO_EC_MSG_TELEMETRY_LONG) {
156 		msg.flags |= WILCO_EC_FLAG_EXTENDED_DATA;
157 		msg.response_size = EC_MAILBOX_DATA_SIZE_EXTENDED;
158 	}
159 
160 	ret = wilco_ec_mailbox(debug_info->ec, &msg);
161 	if (ret < 0)
162 		return ret;
163 	debug_info->response_size = ret;
164 
165 	return count;
166 }
167 
168 static ssize_t raw_read(struct file *file, char __user *user_buf, size_t count,
169 			loff_t *ppos)
170 {
171 	int fmt_len = 0;
172 
173 	if (debug_info->response_size) {
174 		fmt_len = hex_dump_to_buffer(debug_info->raw_data,
175 					     debug_info->response_size,
176 					     16, 1, debug_info->formatted_data,
177 					     FORMATTED_BUFFER_SIZE, true);
178 		/* Only return response the first time it is read */
179 		debug_info->response_size = 0;
180 	}
181 
182 	return simple_read_from_buffer(user_buf, count, ppos,
183 				       debug_info->formatted_data, fmt_len);
184 }
185 
186 static const struct file_operations fops_raw = {
187 	.owner = THIS_MODULE,
188 	.read = raw_read,
189 	.write = raw_write,
190 	.llseek = no_llseek,
191 };
192 
193 /**
194  * wilco_ec_debugfs_probe() - Create the debugfs node
195  * @pdev: The platform device, probably created in core.c
196  *
197  * Try to create a debugfs node. If it fails, then we don't want to change
198  * behavior at all, this is for debugging after all. Just fail silently.
199  *
200  * Return: 0 always.
201  */
202 static int wilco_ec_debugfs_probe(struct platform_device *pdev)
203 {
204 	struct wilco_ec_device *ec = dev_get_drvdata(pdev->dev.parent);
205 
206 	debug_info = devm_kzalloc(&pdev->dev, sizeof(*debug_info), GFP_KERNEL);
207 	if (!debug_info)
208 		return 0;
209 	debug_info->ec = ec;
210 	debug_info->dir = debugfs_create_dir("wilco_ec", NULL);
211 	if (!debug_info->dir)
212 		return 0;
213 	debugfs_create_file("raw", 0644, debug_info->dir, NULL, &fops_raw);
214 
215 	return 0;
216 }
217 
218 static int wilco_ec_debugfs_remove(struct platform_device *pdev)
219 {
220 	debugfs_remove_recursive(debug_info->dir);
221 
222 	return 0;
223 }
224 
225 static struct platform_driver wilco_ec_debugfs_driver = {
226 	.driver = {
227 		.name = DRV_NAME,
228 	},
229 	.probe = wilco_ec_debugfs_probe,
230 	.remove = wilco_ec_debugfs_remove,
231 };
232 
233 module_platform_driver(wilco_ec_debugfs_driver);
234 
235 MODULE_ALIAS("platform:" DRV_NAME);
236 MODULE_AUTHOR("Nick Crews <ncrews@chromium.org>");
237 MODULE_LICENSE("GPL v2");
238 MODULE_DESCRIPTION("Wilco EC debugfs driver");
239