f_subset.c

  1// SPDX-License-Identifier: GPL-2.0+
  2/*
  3 * f_subset.c -- "CDC Subset" Ethernet link function driver
  4 *
  5 * Copyright (C) 2003-2005,2008 David Brownell
  6 * Copyright (C) 2008 Nokia Corporation
  7 */
  8
  9#include <linux/cleanup.h>
 10#include <linux/slab.h>
 11#include <linux/kernel.h>
 12#include <linux/module.h>
 13#include <linux/device.h>
 14#include <linux/etherdevice.h>
 15
 16#include "u_ether.h"
 17#include "u_ether_configfs.h"
 18#include "u_gether.h"
 19
 20/*
 21 * This function packages a simple "CDC Subset" Ethernet port with no real
 22 * control mechanisms; just raw data transfer over two bulk endpoints.
 23 * The data transfer model is exactly that of CDC Ethernet, which is
 24 * why we call it the "CDC Subset".
 25 *
 26 * Because it's not standardized, this has some interoperability issues.
 27 * They mostly relate to driver binding, since the data transfer model is
 28 * so simple (CDC Ethernet).  The original versions of this protocol used
 29 * specific product/vendor IDs:  byteswapped IDs for Digital Equipment's
 30 * SA-1100 "Itsy" board, which could run Linux 2.4 kernels and supported
 31 * daughtercards with USB peripheral connectors.  (It was used more often
 32 * with other boards, using the Itsy identifiers.)  Linux hosts recognized
 33 * this with CONFIG_USB_ARMLINUX; these devices have only one configuration
 34 * and one interface.
 35 *
 36 * At some point, MCCI defined a (nonconformant) CDC MDLM variant called
 37 * "SAFE", which happens to have a mode which is identical to the "CDC
 38 * Subset" in terms of data transfer and lack of control model.  This was
 39 * adopted by later Sharp Zaurus models, and by some other software which
 40 * Linux hosts recognize with CONFIG_USB_NET_ZAURUS.
 41 *
 42 * Because Microsoft's RNDIS drivers are far from robust, we added a few
 43 * descriptors to the CDC Subset code, making this code look like a SAFE
 44 * implementation.  This lets you use MCCI's host side MS-Windows drivers
 45 * if you get fed up with RNDIS.  It also makes it easier for composite
 46 * drivers to work, since they can use class based binding instead of
 47 * caring about specific product and vendor IDs.
 48 */
 49
 50struct f_gether {
 51	struct gether			port;
 52
 53	char				ethaddr[14];
 54};
 55
 56static inline struct f_gether *func_to_geth(struct usb_function *f)
 57{
 58	return container_of(f, struct f_gether, port.func);
 59}
 60
 61/*-------------------------------------------------------------------------*/
 62
 63/*
 64 * "Simple" CDC-subset option is a simple vendor-neutral model that most
 65 * full speed controllers can handle:  one interface, two bulk endpoints.
 66 * To assist host side drivers, we fancy it up a bit, and add descriptors so
 67 * some host side drivers will understand it as a "SAFE" variant.
 68 *
 69 * "SAFE" loosely follows CDC WMC MDLM, violating the spec in various ways.
 70 * Data endpoints live in the control interface, there's no data interface.
 71 * And it's not used to talk to a cell phone radio.
 72 */
 73
 74/* interface descriptor: */
 75
 76static struct usb_interface_descriptor subset_data_intf = {
 77	.bLength =		sizeof subset_data_intf,
 78	.bDescriptorType =	USB_DT_INTERFACE,
 79
 80	/* .bInterfaceNumber = DYNAMIC */
 81	.bAlternateSetting =	0,
 82	.bNumEndpoints =	2,
 83	.bInterfaceClass =      USB_CLASS_COMM,
 84	.bInterfaceSubClass =	USB_CDC_SUBCLASS_MDLM,
 85	.bInterfaceProtocol =	0,
 86	/* .iInterface = DYNAMIC */
 87};
 88
 89static struct usb_cdc_header_desc mdlm_header_desc = {
 90	.bLength =		sizeof mdlm_header_desc,
 91	.bDescriptorType =	USB_DT_CS_INTERFACE,
 92	.bDescriptorSubType =	USB_CDC_HEADER_TYPE,
 93
 94	.bcdCDC =		cpu_to_le16(0x0110),
 95};
 96
 97static struct usb_cdc_mdlm_desc mdlm_desc = {
 98	.bLength =		sizeof mdlm_desc,
 99	.bDescriptorType =	USB_DT_CS_INTERFACE,
100	.bDescriptorSubType =	USB_CDC_MDLM_TYPE,
101
102	.bcdVersion =		cpu_to_le16(0x0100),
103	.bGUID = {
104		0x5d, 0x34, 0xcf, 0x66, 0x11, 0x18, 0x11, 0xd6,
105		0xa2, 0x1a, 0x00, 0x01, 0x02, 0xca, 0x9a, 0x7f,
106	},
107};
108
109/* since "usb_cdc_mdlm_detail_desc" is a variable length structure, we
110 * can't really use its struct.  All we do here is say that we're using
111 * the submode of "SAFE" which directly matches the CDC Subset.
112 */
113static u8 mdlm_detail_desc[] = {
114	6,
115	USB_DT_CS_INTERFACE,
116	USB_CDC_MDLM_DETAIL_TYPE,
117
118	0,	/* "SAFE" */
119	0,	/* network control capabilities (none) */
120	0,	/* network data capabilities ("raw" encapsulation) */
121};
122
123static struct usb_cdc_ether_desc ether_desc = {
124	.bLength =		sizeof ether_desc,
125	.bDescriptorType =	USB_DT_CS_INTERFACE,
126	.bDescriptorSubType =	USB_CDC_ETHERNET_TYPE,
127
128	/* this descriptor actually adds value, surprise! */
129	/* .iMACAddress = DYNAMIC */
130	.bmEthernetStatistics =	cpu_to_le32(0), /* no statistics */
131	.wMaxSegmentSize =	cpu_to_le16(ETH_FRAME_LEN),
132	.wNumberMCFilters =	cpu_to_le16(0),
133	.bNumberPowerFilters =	0,
134};
135
136/* full speed support: */
137
138static struct usb_endpoint_descriptor fs_subset_in_desc = {
139	.bLength =		USB_DT_ENDPOINT_SIZE,
140	.bDescriptorType =	USB_DT_ENDPOINT,
141
142	.bEndpointAddress =	USB_DIR_IN,
143	.bmAttributes =		USB_ENDPOINT_XFER_BULK,
144};
145
146static struct usb_endpoint_descriptor fs_subset_out_desc = {
147	.bLength =		USB_DT_ENDPOINT_SIZE,
148	.bDescriptorType =	USB_DT_ENDPOINT,
149
150	.bEndpointAddress =	USB_DIR_OUT,
151	.bmAttributes =		USB_ENDPOINT_XFER_BULK,
152};
153
154static struct usb_descriptor_header *fs_eth_function[] = {
155	(struct usb_descriptor_header *) &subset_data_intf,
156	(struct usb_descriptor_header *) &mdlm_header_desc,
157	(struct usb_descriptor_header *) &mdlm_desc,
158	(struct usb_descriptor_header *) &mdlm_detail_desc,
159	(struct usb_descriptor_header *) &ether_desc,
160	(struct usb_descriptor_header *) &fs_subset_in_desc,
161	(struct usb_descriptor_header *) &fs_subset_out_desc,
162	NULL,
163};
164
165/* high speed support: */
166
167static struct usb_endpoint_descriptor hs_subset_in_desc = {
168	.bLength =		USB_DT_ENDPOINT_SIZE,
169	.bDescriptorType =	USB_DT_ENDPOINT,
170
171	.bmAttributes =		USB_ENDPOINT_XFER_BULK,
172	.wMaxPacketSize =	cpu_to_le16(512),
173};
174
175static struct usb_endpoint_descriptor hs_subset_out_desc = {
176	.bLength =		USB_DT_ENDPOINT_SIZE,
177	.bDescriptorType =	USB_DT_ENDPOINT,
178
179	.bmAttributes =		USB_ENDPOINT_XFER_BULK,
180	.wMaxPacketSize =	cpu_to_le16(512),
181};
182
183static struct usb_descriptor_header *hs_eth_function[] = {
184	(struct usb_descriptor_header *) &subset_data_intf,
185	(struct usb_descriptor_header *) &mdlm_header_desc,
186	(struct usb_descriptor_header *) &mdlm_desc,
187	(struct usb_descriptor_header *) &mdlm_detail_desc,
188	(struct usb_descriptor_header *) &ether_desc,
189	(struct usb_descriptor_header *) &hs_subset_in_desc,
190	(struct usb_descriptor_header *) &hs_subset_out_desc,
191	NULL,
192};
193
194/* super speed support: */
195
196static struct usb_endpoint_descriptor ss_subset_in_desc = {
197	.bLength =		USB_DT_ENDPOINT_SIZE,
198	.bDescriptorType =	USB_DT_ENDPOINT,
199
200	.bmAttributes =		USB_ENDPOINT_XFER_BULK,
201	.wMaxPacketSize =	cpu_to_le16(1024),
202};
203
204static struct usb_endpoint_descriptor ss_subset_out_desc = {
205	.bLength =		USB_DT_ENDPOINT_SIZE,
206	.bDescriptorType =	USB_DT_ENDPOINT,
207
208	.bmAttributes =		USB_ENDPOINT_XFER_BULK,
209	.wMaxPacketSize =	cpu_to_le16(1024),
210};
211
212static struct usb_ss_ep_comp_descriptor ss_subset_bulk_comp_desc = {
213	.bLength =		sizeof ss_subset_bulk_comp_desc,
214	.bDescriptorType =	USB_DT_SS_ENDPOINT_COMP,
215
216	/* the following 2 values can be tweaked if necessary */
217	/* .bMaxBurst =		0, */
218	/* .bmAttributes =	0, */
219};
220
221static struct usb_descriptor_header *ss_eth_function[] = {
222	(struct usb_descriptor_header *) &subset_data_intf,
223	(struct usb_descriptor_header *) &mdlm_header_desc,
224	(struct usb_descriptor_header *) &mdlm_desc,
225	(struct usb_descriptor_header *) &mdlm_detail_desc,
226	(struct usb_descriptor_header *) &ether_desc,
227	(struct usb_descriptor_header *) &ss_subset_in_desc,
228	(struct usb_descriptor_header *) &ss_subset_bulk_comp_desc,
229	(struct usb_descriptor_header *) &ss_subset_out_desc,
230	(struct usb_descriptor_header *) &ss_subset_bulk_comp_desc,
231	NULL,
232};
233
234/* string descriptors: */
235
236static struct usb_string geth_string_defs[] = {
237	[0].s = "CDC Ethernet Subset/SAFE",
238	[1].s = "",
239	{  } /* end of list */
240};
241
242static struct usb_gadget_strings geth_string_table = {
243	.language =		0x0409,	/* en-us */
244	.strings =		geth_string_defs,
245};
246
247static struct usb_gadget_strings *geth_strings[] = {
248	&geth_string_table,
249	NULL,
250};
251
252/*-------------------------------------------------------------------------*/
253
254static int geth_set_alt(struct usb_function *f, unsigned intf, unsigned alt)
255{
256	struct f_gether		*geth = func_to_geth(f);
257	struct usb_composite_dev *cdev = f->config->cdev;
258	struct net_device	*net;
259
260	/* we know alt == 0, so this is an activation or a reset */
261
262	if (geth->port.in_ep->enabled) {
263		DBG(cdev, "reset cdc subset\n");
264		gether_disconnect(&geth->port);
265	}
266
267	DBG(cdev, "init + activate cdc subset\n");
268	if (config_ep_by_speed(cdev->gadget, f, geth->port.in_ep) ||
269	    config_ep_by_speed(cdev->gadget, f, geth->port.out_ep)) {
270		geth->port.in_ep->desc = NULL;
271		geth->port.out_ep->desc = NULL;
272		return -EINVAL;
273	}
274
275	net = gether_connect(&geth->port);
276	return PTR_ERR_OR_ZERO(net);
277}
278
279static void geth_disable(struct usb_function *f)
280{
281	struct f_gether	*geth = func_to_geth(f);
282	struct usb_composite_dev *cdev = f->config->cdev;
283
284	DBG(cdev, "net deactivated\n");
285	gether_disconnect(&geth->port);
286}
287
288/*-------------------------------------------------------------------------*/
289
290/* serial function driver setup/binding */
291
292static int
293geth_bind(struct usb_configuration *c, struct usb_function *f)
294{
295	struct usb_composite_dev *cdev = c->cdev;
296	struct f_gether		*geth = func_to_geth(f);
297	struct usb_string	*us;
298	int			status;
299	struct usb_ep		*ep;
300
301	struct f_gether_opts	*gether_opts;
302	struct net_device	*net __free(detach_gadget) = NULL;
303
304	gether_opts = container_of(f->fi, struct f_gether_opts, func_inst);
305
306	scoped_guard(mutex, &gether_opts->lock)
307		if (gether_opts->bind_count == 0 && !gether_opts->bound) {
308			if (!device_is_registered(&gether_opts->net->dev)) {
309				gether_set_gadget(gether_opts->net, cdev->gadget);
310				status = gether_register_netdev(gether_opts->net);
311			} else
312				status = gether_attach_gadget(gether_opts->net, cdev->gadget);
313
314			if (status)
315				return status;
316			net = gether_opts->net;
317		}
318
319	us = usb_gstrings_attach(cdev, geth_strings,
320				 ARRAY_SIZE(geth_string_defs));
321	if (IS_ERR(us))
322		return PTR_ERR(us);
323
324	subset_data_intf.iInterface = us[0].id;
325	ether_desc.iMACAddress = us[1].id;
326
327	/* allocate instance-specific interface IDs */
328	status = usb_interface_id(c, f);
329	if (status < 0)
330		return status;
331	subset_data_intf.bInterfaceNumber = status;
332
333	/* allocate instance-specific endpoints */
334	ep = usb_ep_autoconfig(cdev->gadget, &fs_subset_in_desc);
335	if (!ep)
336		return -ENODEV;
337	geth->port.in_ep = ep;
338
339	ep = usb_ep_autoconfig(cdev->gadget, &fs_subset_out_desc);
340	if (!ep)
341		return -ENODEV;
342	geth->port.out_ep = ep;
343
344	/* support all relevant hardware speeds... we expect that when
345	 * hardware is dual speed, all bulk-capable endpoints work at
346	 * both speeds
347	 */
348	hs_subset_in_desc.bEndpointAddress = fs_subset_in_desc.bEndpointAddress;
349	hs_subset_out_desc.bEndpointAddress =
350		fs_subset_out_desc.bEndpointAddress;
351
352	ss_subset_in_desc.bEndpointAddress = fs_subset_in_desc.bEndpointAddress;
353	ss_subset_out_desc.bEndpointAddress =
354		fs_subset_out_desc.bEndpointAddress;
355
356	status = usb_assign_descriptors(f, fs_eth_function, hs_eth_function,
357			ss_eth_function, ss_eth_function);
358	if (status)
359		return status;
360
361	/* NOTE:  all that is done without knowing or caring about
362	 * the network link ... which is unavailable to this code
363	 * until we're activated via set_alt().
364	 */
365
366	gether_opts->bind_count++;
367	retain_and_null_ptr(net);
368
369	DBG(cdev, "CDC Subset: IN/%s OUT/%s\n",
370			geth->port.in_ep->name, geth->port.out_ep->name);
371	return 0;
372}
373
374static inline struct f_gether_opts *to_f_gether_opts(struct config_item *item)
375{
376	return container_of(to_config_group(item), struct f_gether_opts,
377			    func_inst.group);
378}
379
380/* f_gether_item_ops */
381USB_ETHERNET_CONFIGFS_ITEM(gether);
382
383/* f_gether_opts_dev_addr */
384USB_ETHERNET_CONFIGFS_ITEM_ATTR_DEV_ADDR(gether);
385
386/* f_gether_opts_host_addr */
387USB_ETHERNET_CONFIGFS_ITEM_ATTR_HOST_ADDR(gether);
388
389/* f_gether_opts_qmult */
390USB_ETHERNET_CONFIGFS_ITEM_ATTR_QMULT(gether);
391
392/* f_gether_opts_ifname */
393USB_ETHERNET_CONFIGFS_ITEM_ATTR_IFNAME(gether);
394
395static struct configfs_attribute *gether_attrs[] = {
396	&gether_opts_attr_dev_addr,
397	&gether_opts_attr_host_addr,
398	&gether_opts_attr_qmult,
399	&gether_opts_attr_ifname,
400	NULL,
401};
402
403static const struct config_item_type gether_func_type = {
404	.ct_item_ops	= &gether_item_ops,
405	.ct_attrs	= gether_attrs,
406	.ct_owner	= THIS_MODULE,
407};
408
409static void geth_free_inst(struct usb_function_instance *f)
410{
411	struct f_gether_opts *opts;
412
413	opts = container_of(f, struct f_gether_opts, func_inst);
414	if (device_is_registered(&opts->net->dev))
415		gether_cleanup(netdev_priv(opts->net));
416	else
417		free_netdev(opts->net);
418	kfree(opts);
419}
420
421static struct usb_function_instance *geth_alloc_inst(void)
422{
423	struct f_gether_opts *opts;
424
425	opts = kzalloc(sizeof(*opts), GFP_KERNEL);
426	if (!opts)
427		return ERR_PTR(-ENOMEM);
428	mutex_init(&opts->lock);
429	opts->func_inst.free_func_inst = geth_free_inst;
430	opts->net = gether_setup_default();
431	if (IS_ERR(opts->net)) {
432		struct net_device *net = opts->net;
433		kfree(opts);
434		return ERR_CAST(net);
435	}
436
437	config_group_init_type_name(&opts->func_inst.group, "",
438				    &gether_func_type);
439
440	return &opts->func_inst;
441}
442
443static void geth_free(struct usb_function *f)
444{
445	struct f_gether *eth;
446	struct f_gether_opts *opts;
447
448	opts = container_of(f->fi, struct f_gether_opts, func_inst);
449
450	eth = func_to_geth(f);
451	scoped_guard(mutex, &opts->lock)
452		opts->refcnt--;
453	kfree(eth);
454}
455
456static void geth_unbind(struct usb_configuration *c, struct usb_function *f)
457{
458	struct f_gether_opts *opts;
459
460	opts = container_of(f->fi, struct f_gether_opts, func_inst);
461
462	geth_string_defs[0].id = 0;
463	usb_free_all_descriptors(f);
464
465	opts->bind_count--;
466	if (opts->bind_count == 0 && !opts->bound)
467		gether_detach_gadget(opts->net);
468}
469
470static struct usb_function *geth_alloc(struct usb_function_instance *fi)
471{
472	struct f_gether	*geth;
473	struct f_gether_opts *opts;
474	int status;
475
476	/* allocate and initialize one new instance */
477	geth = kzalloc(sizeof(*geth), GFP_KERNEL);
478	if (!geth)
479		return ERR_PTR(-ENOMEM);
480
481	opts = container_of(fi, struct f_gether_opts, func_inst);
482
483	mutex_lock(&opts->lock);
484	opts->refcnt++;
485	/* export host's Ethernet address in CDC format */
486	status = gether_get_host_addr_cdc(opts->net, geth->ethaddr,
487					  sizeof(geth->ethaddr));
488	if (status < 12) {
489		kfree(geth);
490		mutex_unlock(&opts->lock);
491		return ERR_PTR(-EINVAL);
492	}
493	geth_string_defs[1].s = geth->ethaddr;
494
495	geth->port.ioport = netdev_priv(opts->net);
496	mutex_unlock(&opts->lock);
497	geth->port.cdc_filter = DEFAULT_FILTER;
498
499	geth->port.func.name = "cdc_subset";
500	geth->port.func.bind = geth_bind;
501	geth->port.func.unbind = geth_unbind;
502	geth->port.func.set_alt = geth_set_alt;
503	geth->port.func.disable = geth_disable;
504	geth->port.func.free_func = geth_free;
505
506	return &geth->port.func;
507}
508
509DECLARE_USB_FUNCTION_INIT(geth, geth_alloc_inst, geth_alloc);
510MODULE_DESCRIPTION("\"CDC Subset\" Ethernet link function driver");
511MODULE_LICENSE("GPL");
512MODULE_AUTHOR("David Brownell");