1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * driver for the i2c-tiny-usb adapter - 1.0
4  * http://www.harbaum.org/till/i2c_tiny_usb
5  *
6  * Copyright (C) 2006-2007 Till Harbaum (Till@Harbaum.org)
7  */
8 
9 #include <linux/kernel.h>
10 #include <linux/errno.h>
11 #include <linux/module.h>
12 #include <linux/slab.h>
13 #include <linux/types.h>
14 
15 /* include interfaces to usb layer */
16 #include <linux/usb.h>
17 
18 /* include interface to i2c layer */
19 #include <linux/i2c.h>
20 
21 /* commands via USB, must match command ids in the firmware */
22 #define CMD_ECHO		0
23 #define CMD_GET_FUNC		1
24 #define CMD_SET_DELAY		2
25 #define CMD_GET_STATUS		3
26 
27 #define CMD_I2C_IO		4
28 #define CMD_I2C_IO_BEGIN	(1<<0)
29 #define CMD_I2C_IO_END		(1<<1)
30 
31 /* i2c bit delay, default is 10us -> 100kHz max
32    (in practice, due to additional delays in the i2c bitbanging
33    code this results in a i2c clock of about 50kHz) */
34 static unsigned short delay = 10;
35 module_param(delay, ushort, 0);
36 MODULE_PARM_DESC(delay, "bit delay in microseconds "
37 		 "(default is 10us for 100kHz max)");
38 
39 static int usb_read(struct i2c_adapter *adapter, int cmd,
40 		    int value, int index, void *data, int len);
41 
42 static int usb_write(struct i2c_adapter *adapter, int cmd,
43 		     int value, int index, void *data, int len);
44 
45 /* ----- begin of i2c layer ---------------------------------------------- */
46 
47 #define STATUS_IDLE		0
48 #define STATUS_ADDRESS_ACK	1
49 #define STATUS_ADDRESS_NAK	2
50 
51 static int usb_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs, int num)
52 {
53 	unsigned char *pstatus;
54 	struct i2c_msg *pmsg;
55 	int i, ret;
56 
57 	dev_dbg(&adapter->dev, "master xfer %d messages:\n", num);
58 
59 	pstatus = kmalloc(sizeof(*pstatus), GFP_KERNEL);
60 	if (!pstatus)
61 		return -ENOMEM;
62 
63 	for (i = 0 ; i < num ; i++) {
64 		int cmd = CMD_I2C_IO;
65 
66 		if (i == 0)
67 			cmd |= CMD_I2C_IO_BEGIN;
68 
69 		if (i == num-1)
70 			cmd |= CMD_I2C_IO_END;
71 
72 		pmsg = &msgs[i];
73 
74 		dev_dbg(&adapter->dev,
75 			"  %d: %s (flags %d) %d bytes to 0x%02x\n",
76 			i, pmsg->flags & I2C_M_RD ? "read" : "write",
77 			pmsg->flags, pmsg->len, pmsg->addr);
78 
79 		/* and directly send the message */
80 		if (pmsg->flags & I2C_M_RD) {
81 			/* read data */
82 			if (usb_read(adapter, cmd,
83 				     pmsg->flags, pmsg->addr,
84 				     pmsg->buf, pmsg->len) != pmsg->len) {
85 				dev_err(&adapter->dev,
86 					"failure reading data\n");
87 				ret = -EIO;
88 				goto out;
89 			}
90 		} else {
91 			/* write data */
92 			if (usb_write(adapter, cmd,
93 				      pmsg->flags, pmsg->addr,
94 				      pmsg->buf, pmsg->len) != pmsg->len) {
95 				dev_err(&adapter->dev,
96 					"failure writing data\n");
97 				ret = -EIO;
98 				goto out;
99 			}
100 		}
101 
102 		/* read status */
103 		if (usb_read(adapter, CMD_GET_STATUS, 0, 0, pstatus, 1) != 1) {
104 			dev_err(&adapter->dev, "failure reading status\n");
105 			ret = -EIO;
106 			goto out;
107 		}
108 
109 		dev_dbg(&adapter->dev, "  status = %d\n", *pstatus);
110 		if (*pstatus == STATUS_ADDRESS_NAK) {
111 			ret = -ENXIO;
112 			goto out;
113 		}
114 	}
115 
116 	ret = i;
117 out:
118 	kfree(pstatus);
119 	return ret;
120 }
121 
122 static u32 usb_func(struct i2c_adapter *adapter)
123 {
124 	__le32 *pfunc;
125 	u32 ret;
126 
127 	pfunc = kmalloc(sizeof(*pfunc), GFP_KERNEL);
128 
129 	/* get functionality from adapter */
130 	if (!pfunc || usb_read(adapter, CMD_GET_FUNC, 0, 0, pfunc,
131 			       sizeof(*pfunc)) != sizeof(*pfunc)) {
132 		dev_err(&adapter->dev, "failure reading functionality\n");
133 		ret = 0;
134 		goto out;
135 	}
136 
137 	ret = le32_to_cpup(pfunc);
138 out:
139 	kfree(pfunc);
140 	return ret;
141 }
142 
143 /* This is the actual algorithm we define */
144 static const struct i2c_algorithm usb_algorithm = {
145 	.master_xfer	= usb_xfer,
146 	.functionality	= usb_func,
147 };
148 
149 /* ----- end of i2c layer ------------------------------------------------ */
150 
151 /* ----- begin of usb layer ---------------------------------------------- */
152 
153 /*
154  * Initially the usb i2c interface uses a vid/pid pair donated by
155  * Future Technology Devices International Ltd., later a pair was
156  * bought from EZPrototypes
157  */
158 static const struct usb_device_id i2c_tiny_usb_table[] = {
159 	{ USB_DEVICE(0x0403, 0xc631) },   /* FTDI */
160 	{ USB_DEVICE(0x1c40, 0x0534) },   /* EZPrototypes */
161 	{ }                               /* Terminating entry */
162 };
163 
164 MODULE_DEVICE_TABLE(usb, i2c_tiny_usb_table);
165 
166 /* Structure to hold all of our device specific stuff */
167 struct i2c_tiny_usb {
168 	struct usb_device *usb_dev; /* the usb device for this device */
169 	struct usb_interface *interface; /* the interface for this device */
170 	struct i2c_adapter adapter; /* i2c related things */
171 };
172 
173 static int usb_read(struct i2c_adapter *adapter, int cmd,
174 		    int value, int index, void *data, int len)
175 {
176 	struct i2c_tiny_usb *dev = (struct i2c_tiny_usb *)adapter->algo_data;
177 	void *dmadata = kmalloc(len, GFP_KERNEL);
178 	int ret;
179 
180 	if (!dmadata)
181 		return -ENOMEM;
182 
183 	/* do control transfer */
184 	ret = usb_control_msg(dev->usb_dev, usb_rcvctrlpipe(dev->usb_dev, 0),
185 			       cmd, USB_TYPE_VENDOR | USB_RECIP_INTERFACE |
186 			       USB_DIR_IN, value, index, dmadata, len, 2000);
187 
188 	memcpy(data, dmadata, len);
189 	kfree(dmadata);
190 	return ret;
191 }
192 
193 static int usb_write(struct i2c_adapter *adapter, int cmd,
194 		     int value, int index, void *data, int len)
195 {
196 	struct i2c_tiny_usb *dev = (struct i2c_tiny_usb *)adapter->algo_data;
197 	void *dmadata = kmemdup(data, len, GFP_KERNEL);
198 	int ret;
199 
200 	if (!dmadata)
201 		return -ENOMEM;
202 
203 	/* do control transfer */
204 	ret = usb_control_msg(dev->usb_dev, usb_sndctrlpipe(dev->usb_dev, 0),
205 			       cmd, USB_TYPE_VENDOR | USB_RECIP_INTERFACE,
206 			       value, index, dmadata, len, 2000);
207 
208 	kfree(dmadata);
209 	return ret;
210 }
211 
212 static void i2c_tiny_usb_free(struct i2c_tiny_usb *dev)
213 {
214 	usb_put_dev(dev->usb_dev);
215 	kfree(dev);
216 }
217 
218 static int i2c_tiny_usb_probe(struct usb_interface *interface,
219 			      const struct usb_device_id *id)
220 {
221 	struct i2c_tiny_usb *dev;
222 	int retval = -ENOMEM;
223 	u16 version;
224 
225 	if (interface->intf_assoc &&
226 	    interface->intf_assoc->bFunctionClass != USB_CLASS_VENDOR_SPEC)
227 		return -ENODEV;
228 
229 	dev_dbg(&interface->dev, "probing usb device\n");
230 
231 	/* allocate memory for our device state and initialize it */
232 	dev = kzalloc(sizeof(*dev), GFP_KERNEL);
233 	if (!dev)
234 		goto error;
235 
236 	dev->usb_dev = usb_get_dev(interface_to_usbdev(interface));
237 	dev->interface = interface;
238 
239 	/* save our data pointer in this interface device */
240 	usb_set_intfdata(interface, dev);
241 
242 	version = le16_to_cpu(dev->usb_dev->descriptor.bcdDevice);
243 	dev_info(&interface->dev,
244 		 "version %x.%02x found at bus %03d address %03d\n",
245 		 version >> 8, version & 0xff,
246 		 dev->usb_dev->bus->busnum, dev->usb_dev->devnum);
247 
248 	/* setup i2c adapter description */
249 	dev->adapter.owner = THIS_MODULE;
250 	dev->adapter.class = I2C_CLASS_HWMON;
251 	dev->adapter.algo = &usb_algorithm;
252 	dev->adapter.algo_data = dev;
253 	snprintf(dev->adapter.name, sizeof(dev->adapter.name),
254 		 "i2c-tiny-usb at bus %03d device %03d",
255 		 dev->usb_dev->bus->busnum, dev->usb_dev->devnum);
256 
257 	if (usb_write(&dev->adapter, CMD_SET_DELAY, delay, 0, NULL, 0) != 0) {
258 		dev_err(&dev->adapter.dev,
259 			"failure setting delay to %dus\n", delay);
260 		retval = -EIO;
261 		goto error;
262 	}
263 
264 	dev->adapter.dev.parent = &dev->interface->dev;
265 
266 	/* and finally attach to i2c layer */
267 	i2c_add_adapter(&dev->adapter);
268 
269 	/* inform user about successful attachment to i2c layer */
270 	dev_info(&dev->adapter.dev, "connected i2c-tiny-usb device\n");
271 
272 	return 0;
273 
274  error:
275 	if (dev)
276 		i2c_tiny_usb_free(dev);
277 
278 	return retval;
279 }
280 
281 static void i2c_tiny_usb_disconnect(struct usb_interface *interface)
282 {
283 	struct i2c_tiny_usb *dev = usb_get_intfdata(interface);
284 
285 	i2c_del_adapter(&dev->adapter);
286 	usb_set_intfdata(interface, NULL);
287 	i2c_tiny_usb_free(dev);
288 
289 	dev_dbg(&interface->dev, "disconnected\n");
290 }
291 
292 static struct usb_driver i2c_tiny_usb_driver = {
293 	.name		= "i2c-tiny-usb",
294 	.probe		= i2c_tiny_usb_probe,
295 	.disconnect	= i2c_tiny_usb_disconnect,
296 	.id_table	= i2c_tiny_usb_table,
297 };
298 
299 module_usb_driver(i2c_tiny_usb_driver);
300 
301 /* ----- end of usb layer ------------------------------------------------ */
302 
303 MODULE_AUTHOR("Till Harbaum <Till@Harbaum.org>");
304 MODULE_DESCRIPTION("i2c-tiny-usb driver v1.0");
305 MODULE_LICENSE("GPL");
306