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1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * USB CDC EEM network interface driver
4 * Copyright (C) 2009 Oberthur Technologies
5 * by Omar Laazimani, Olivier Condemine
6 */
7
8#include <linux/module.h>
9#include <linux/netdevice.h>
10#include <linux/etherdevice.h>
11#include <linux/ctype.h>
12#include <linux/ethtool.h>
13#include <linux/workqueue.h>
14#include <linux/mii.h>
15#include <linux/usb.h>
16#include <linux/crc32.h>
17#include <linux/usb/cdc.h>
18#include <linux/usb/usbnet.h>
19#include <linux/gfp.h>
20#include <linux/if_vlan.h>
21
22
23/*
24 * This driver is an implementation of the CDC "Ethernet Emulation
25 * Model" (EEM) specification, which encapsulates Ethernet frames
26 * for transport over USB using a simpler USB device model than the
27 * previous CDC "Ethernet Control Model" (ECM, or "CDC Ethernet").
28 *
29 * For details, see https://usb.org/sites/default/files/CDC_EEM10.pdf
30 *
31 * This version has been tested with GIGAntIC WuaoW SIM Smart Card on 2.6.24,
32 * 2.6.27 and 2.6.30rc2 kernel.
33 * It has also been validated on Openmoko Om 2008.12 (based on 2.6.24 kernel).
34 * build on 23-April-2009
35 */
36
37#define EEM_HEAD 2 /* 2 byte header */
38
39/*-------------------------------------------------------------------------*/
40
41static void eem_linkcmd_complete(struct urb *urb)
42{
43 dev_kfree_skb(urb->context);
44 usb_free_urb(urb);
45}
46
47static void eem_linkcmd(struct usbnet *dev, struct sk_buff *skb)
48{
49 struct urb *urb;
50 int status;
51
52 urb = usb_alloc_urb(0, GFP_ATOMIC);
53 if (!urb)
54 goto fail;
55
56 usb_fill_bulk_urb(urb, dev->udev, dev->out,
57 skb->data, skb->len, eem_linkcmd_complete, skb);
58
59 status = usb_submit_urb(urb, GFP_ATOMIC);
60 if (status) {
61 usb_free_urb(urb);
62fail:
63 dev_kfree_skb(skb);
64 netdev_warn(dev->net, "link cmd failure\n");
65 return;
66 }
67}
68
69static int eem_bind(struct usbnet *dev, struct usb_interface *intf)
70{
71 int status = 0;
72
73 status = usbnet_get_endpoints(dev, intf);
74 if (status < 0)
75 return status;
76
77 /* no jumbogram (16K) support for now */
78
79 dev->net->hard_header_len += EEM_HEAD + ETH_FCS_LEN + VLAN_HLEN;
80 dev->hard_mtu = dev->net->mtu + dev->net->hard_header_len;
81
82 return 0;
83}
84
85/*
86 * EEM permits packing multiple Ethernet frames into USB transfers
87 * (a "bundle"), but for TX we don't try to do that.
88 */
89static struct sk_buff *eem_tx_fixup(struct usbnet *dev, struct sk_buff *skb,
90 gfp_t flags)
91{
92 struct sk_buff *skb2 = NULL;
93 u16 len = skb->len;
94 u32 crc = 0;
95 int padlen = 0;
96
97 /* When ((len + EEM_HEAD + ETH_FCS_LEN) % dev->maxpacket) is
98 * zero, stick two bytes of zero length EEM packet on the end.
99 * Else the framework would add invalid single byte padding,
100 * since it can't know whether ZLPs will be handled right by
101 * all the relevant hardware and software.
102 */
103 if (!((len + EEM_HEAD + ETH_FCS_LEN) % dev->maxpacket))
104 padlen += 2;
105
106 if (!skb_cloned(skb)) {
107 int headroom = skb_headroom(skb);
108 int tailroom = skb_tailroom(skb);
109
110 if ((tailroom >= ETH_FCS_LEN + padlen) &&
111 (headroom >= EEM_HEAD))
112 goto done;
113
114 if ((headroom + tailroom)
115 > (EEM_HEAD + ETH_FCS_LEN + padlen)) {
116 skb->data = memmove(skb->head +
117 EEM_HEAD,
118 skb->data,
119 skb->len);
120 skb_set_tail_pointer(skb, len);
121 goto done;
122 }
123 }
124
125 skb2 = skb_copy_expand(skb, EEM_HEAD, ETH_FCS_LEN + padlen, flags);
126 dev_kfree_skb_any(skb);
127 if (!skb2)
128 return NULL;
129
130 skb = skb2;
131
132done:
133 /* we don't use the "no Ethernet CRC" option */
134 crc = crc32_le(~0, skb->data, skb->len);
135 crc = ~crc;
136
137 put_unaligned_le32(crc, skb_put(skb, 4));
138
139 /* EEM packet header format:
140 * b0..13: length of ethernet frame
141 * b14: bmCRC (1 == valid Ethernet CRC)
142 * b15: bmType (0 == data)
143 */
144 len = skb->len;
145 put_unaligned_le16(BIT(14) | len, skb_push(skb, 2));
146
147 /* Bundle a zero length EEM packet if needed */
148 if (padlen)
149 put_unaligned_le16(0, skb_put(skb, 2));
150
151 return skb;
152}
153
154static int eem_rx_fixup(struct usbnet *dev, struct sk_buff *skb)
155{
156 /*
157 * Our task here is to strip off framing, leaving skb with one
158 * data frame for the usbnet framework code to process. But we
159 * may have received multiple EEM payloads, or command payloads.
160 * So we must process _everything_ as if it's a header, except
161 * maybe the last data payload
162 *
163 * REVISIT the framework needs updating so that when we consume
164 * all payloads (the last or only message was a command, or a
165 * zero length EEM packet) that is not accounted as an rx_error.
166 */
167 do {
168 struct sk_buff *skb2 = NULL;
169 u16 header;
170 u16 len = 0;
171
172 /* incomplete EEM header? */
173 if (skb->len < EEM_HEAD)
174 return 0;
175
176 /*
177 * EEM packet header format:
178 * b0..14: EEM type dependent (Data or Command)
179 * b15: bmType
180 */
181 header = get_unaligned_le16(skb->data);
182 skb_pull(skb, EEM_HEAD);
183
184 /*
185 * The bmType bit helps to denote when EEM
186 * packet is data or command :
187 * bmType = 0 : EEM data payload
188 * bmType = 1 : EEM (link) command
189 */
190 if (header & BIT(15)) {
191 u16 bmEEMCmd;
192
193 /*
194 * EEM (link) command packet:
195 * b0..10: bmEEMCmdParam
196 * b11..13: bmEEMCmd
197 * b14: bmReserved (must be 0)
198 * b15: 1 (EEM command)
199 */
200 if (header & BIT(14)) {
201 netdev_dbg(dev->net, "reserved command %04x\n",
202 header);
203 continue;
204 }
205
206 bmEEMCmd = (header >> 11) & 0x7;
207 switch (bmEEMCmd) {
208
209 /* Responding to echo requests is mandatory. */
210 case 0: /* Echo command */
211 len = header & 0x7FF;
212
213 /* bogus command? */
214 if (skb->len < len)
215 return 0;
216
217 skb2 = skb_clone(skb, GFP_ATOMIC);
218 if (unlikely(!skb2))
219 goto next;
220 skb_trim(skb2, len);
221 put_unaligned_le16(BIT(15) | BIT(11) | len,
222 skb_push(skb2, 2));
223 eem_linkcmd(dev, skb2);
224 break;
225
226 /*
227 * Host may choose to ignore hints.
228 * - suspend: peripheral ready to suspend
229 * - response: suggest N millisec polling
230 * - response complete: suggest N sec polling
231 *
232 * Suspend is reported and maybe heeded.
233 */
234 case 2: /* Suspend hint */
235 usbnet_device_suggests_idle(dev);
236 continue;
237 case 3: /* Response hint */
238 case 4: /* Response complete hint */
239 continue;
240
241 /*
242 * Hosts should never receive host-to-peripheral
243 * or reserved command codes; or responses to an
244 * echo command we didn't send.
245 */
246 case 1: /* Echo response */
247 case 5: /* Tickle */
248 default: /* reserved */
249 netdev_warn(dev->net,
250 "unexpected link command %d\n",
251 bmEEMCmd);
252 continue;
253 }
254
255 } else {
256 u32 crc, crc2;
257 int is_last;
258
259 /* zero length EEM packet? */
260 if (header == 0)
261 continue;
262
263 /*
264 * EEM data packet header :
265 * b0..13: length of ethernet frame
266 * b14: bmCRC
267 * b15: 0 (EEM data)
268 */
269 len = header & 0x3FFF;
270
271 /* bogus EEM payload? */
272 if (skb->len < len)
273 return 0;
274
275 /* bogus ethernet frame? */
276 if (len < (ETH_HLEN + ETH_FCS_LEN))
277 goto next;
278
279 /*
280 * Treat the last payload differently: framework
281 * code expects our "fixup" to have stripped off
282 * headers, so "skb" is a data packet (or error).
283 * Else if it's not the last payload, keep "skb"
284 * for further processing.
285 */
286 is_last = (len == skb->len);
287 if (is_last)
288 skb2 = skb;
289 else {
290 skb2 = skb_clone(skb, GFP_ATOMIC);
291 if (unlikely(!skb2))
292 return 0;
293 }
294
295 /*
296 * The bmCRC helps to denote when the CRC field in
297 * the Ethernet frame contains a calculated CRC:
298 * bmCRC = 1 : CRC is calculated
299 * bmCRC = 0 : CRC = 0xDEADBEEF
300 */
301 if (header & BIT(14)) {
302 crc = get_unaligned_le32(skb2->data
303 + len - ETH_FCS_LEN);
304 crc2 = ~crc32_le(~0, skb2->data, skb2->len
305 - ETH_FCS_LEN);
306 } else {
307 crc = get_unaligned_be32(skb2->data
308 + len - ETH_FCS_LEN);
309 crc2 = 0xdeadbeef;
310 }
311 skb_trim(skb2, len - ETH_FCS_LEN);
312
313 if (is_last)
314 return crc == crc2;
315
316 if (unlikely(crc != crc2)) {
317 dev->net->stats.rx_errors++;
318 dev_kfree_skb_any(skb2);
319 } else
320 usbnet_skb_return(dev, skb2);
321 }
322
323next:
324 skb_pull(skb, len);
325 } while (skb->len);
326
327 return 1;
328}
329
330static const struct driver_info eem_info = {
331 .description = "CDC EEM Device",
332 .flags = FLAG_ETHER | FLAG_POINTTOPOINT,
333 .bind = eem_bind,
334 .rx_fixup = eem_rx_fixup,
335 .tx_fixup = eem_tx_fixup,
336};
337
338/*-------------------------------------------------------------------------*/
339
340static const struct usb_device_id products[] = {
341{
342 USB_INTERFACE_INFO(USB_CLASS_COMM, USB_CDC_SUBCLASS_EEM,
343 USB_CDC_PROTO_EEM),
344 .driver_info = (unsigned long) &eem_info,
345},
346{
347 /* EMPTY == end of list */
348},
349};
350MODULE_DEVICE_TABLE(usb, products);
351
352static struct usb_driver eem_driver = {
353 .name = "cdc_eem",
354 .id_table = products,
355 .probe = usbnet_probe,
356 .disconnect = usbnet_disconnect,
357 .suspend = usbnet_suspend,
358 .resume = usbnet_resume,
359 .disable_hub_initiated_lpm = 1,
360};
361
362module_usb_driver(eem_driver);
363
364MODULE_AUTHOR("Omar Laazimani <[email protected]>");
365MODULE_DESCRIPTION("USB CDC EEM");
366MODULE_LICENSE("GPL");