drivers/staging/greybus/es1.c

   1 /*
   2  * Greybus "AP" USB driver for "ES1" controller chips
   3  *
   4  * Copyright 2014-2015 Google Inc.
   5  * Copyright 2014-2015 Linaro Ltd.
   6  *
   7  * Released under the GPLv2 only.
   8  */
   9 #include <linux/kthread.h>
  10 #include <linux/sizes.h>
  11 #include <linux/usb.h>
  12 #include <linux/kfifo.h>
  13 #include <linux/debugfs.h>
  14 #include <asm/unaligned.h>
  15
  16 #include "greybus.h"
  17 #include "kernel_ver.h"
  18 #include "connection.h"
  19
  20 /* Memory sizes for the buffers sent to/from the ES1 controller */
  21 #define ES1_GBUF_MSG_SIZE_MAX   2048
  22
  23 static const struct usb_device_id id_table[] = {
  24         /* Made up numbers for the SVC USB Bridge in ES1 */
  25         { USB_DEVICE(0xffff, 0x0001) },
  26         { },
  27 };
  28 MODULE_DEVICE_TABLE(usb, id_table);
  29
  30 #define APB1_LOG_SIZE           SZ_16K
  31 static struct dentry *apb1_log_dentry;
  32 static struct dentry *apb1_log_enable_dentry;
  33 static struct task_struct *apb1_log_task;
  34 static DEFINE_KFIFO(apb1_log_fifo, char, APB1_LOG_SIZE);
  35
  36 /*
  37  * Number of CPort IN urbs in flight at any point in time.
  38  * Adjust if we are having stalls in the USB buffer due to not enough urbs in
  39  * flight.
  40  */
  41 #define NUM_CPORT_IN_URB        4
  42
  43 /* Number of CPort OUT urbs in flight at any point in time.
  44  * Adjust if we get messages saying we are out of urbs in the system log.
  45  */
  46 #define NUM_CPORT_OUT_URB       8
  47
  48 /* vendor request AP message */
  49 #define REQUEST_SVC             0x01
  50
  51 /* vendor request APB1 log */
  52 #define REQUEST_LOG             0x02
  53
  54 /**
  55  * es1_ap_dev - ES1 USB Bridge to AP structure
  56  * @usb_dev: pointer to the USB device we are.
  57  * @usb_intf: pointer to the USB interface we are bound to.
  58  * @hd: pointer to our greybus_host_device structure
  59  * @control_endpoint: endpoint to send data to SVC
  60  * @cport_in_endpoint: bulk in endpoint for CPort data
  61  * @cport-out_endpoint: bulk out endpoint for CPort data
  62  * @cport_in_urb: array of urbs for the CPort in messages
  63  * @cport_in_buffer: array of buffers for the @cport_in_urb urbs
  64  * @cport_out_urb: array of urbs for the CPort out messages
  65  * @cport_out_urb_busy: array of flags to see if the @cport_out_urb is busy or
  66  *                      not.
  67  * @cport_out_urb_cancelled: array of flags indicating whether the
  68  *                      corresponding @cport_out_urb is being cancelled
  69  * @cport_out_urb_lock: locks the @cport_out_urb_busy "list"
  70  */
  71 struct es1_ap_dev {
  72         struct usb_device *usb_dev;
  73         struct usb_interface *usb_intf;
  74         struct greybus_host_device *hd;
  75
  76         __u8 control_endpoint;
  77         __u8 cport_in_endpoint;
  78         __u8 cport_out_endpoint;
  79
  80         struct urb *cport_in_urb[NUM_CPORT_IN_URB];
  81         u8 *cport_in_buffer[NUM_CPORT_IN_URB];
  82         struct urb *cport_out_urb[NUM_CPORT_OUT_URB];
  83         bool cport_out_urb_busy[NUM_CPORT_OUT_URB];
  84         bool cport_out_urb_cancelled[NUM_CPORT_OUT_URB];
  85         spinlock_t cport_out_urb_lock;
  86 };
  87
  88 static inline struct es1_ap_dev *hd_to_es1(struct greybus_host_device *hd)
  89 {
  90         return (struct es1_ap_dev *)&hd->hd_priv;
  91 }
  92
  93 static void cport_out_callback(struct urb *urb);
  94 static void usb_log_enable(struct es1_ap_dev *es1);
  95 static void usb_log_disable(struct es1_ap_dev *es1);
  96
  97 #define ES1_TIMEOUT     500     /* 500 ms for the SVC to do something */
  98
  99 static struct urb *next_free_urb(struct es1_ap_dev *es1, gfp_t gfp_mask)
 100 {
 101         struct urb *urb = NULL;
 102         unsigned long flags;
 103         int i;
 104
 105         spin_lock_irqsave(&es1->cport_out_urb_lock, flags);
 106
 107         /* Look in our pool of allocated urbs first, as that's the "fastest" */
 108         for (i = 0; i < NUM_CPORT_OUT_URB; ++i) {
 109                 if (es1->cport_out_urb_busy[i] == false &&
 110                                 es1->cport_out_urb_cancelled[i] == false) {
 111                         es1->cport_out_urb_busy[i] = true;
 112                         urb = es1->cport_out_urb[i];
 113                         break;
 114                 }
 115         }
 116         spin_unlock_irqrestore(&es1->cport_out_urb_lock, flags);
 117         if (urb)
 118                 return urb;
 119
 120         /*
 121          * Crap, pool is empty, complain to the syslog and go allocate one
 122          * dynamically as we have to succeed.
 123          */
 124         dev_err(&es1->usb_dev->dev,
 125                 "No free CPort OUT urbs, having to dynamically allocate one!\n");
 126         return usb_alloc_urb(0, gfp_mask);
 127 }
 128
 129 static void free_urb(struct es1_ap_dev *es1, struct urb *urb)
 130 {
 131         unsigned long flags;
 132         int i;
 133         /*
 134          * See if this was an urb in our pool, if so mark it "free", otherwise
 135          * we need to free it ourselves.
 136          */
 137         spin_lock_irqsave(&es1->cport_out_urb_lock, flags);
 138         for (i = 0; i < NUM_CPORT_OUT_URB; ++i) {
 139                 if (urb == es1->cport_out_urb[i]) {
 140                         es1->cport_out_urb_busy[i] = false;
 141                         urb = NULL;
 142                         break;
 143                 }
 144         }
 145         spin_unlock_irqrestore(&es1->cport_out_urb_lock, flags);
 146
 147         /* If urb is not NULL, then we need to free this urb */
 148         usb_free_urb(urb);
 149 }
 150
 151 /*
 152  * We (ab)use the operation-message header pad bytes to transfer the
 153  * cport id in order to minimise overhead.
 154  */
 155 static void
 156 gb_message_cport_pack(struct gb_operation_msg_hdr *header, u16 cport_id)
 157 {
 158         header->pad[0] = cport_id;
 159 }
 160
 161 /* Clear the pad bytes used for the CPort id */
 162 static void gb_message_cport_clear(struct gb_operation_msg_hdr *header)
 163 {
 164         header->pad[0] = 0;
 165 }
 166
 167 /* Extract the CPort id packed into the header, and clear it */
 168 static u16 gb_message_cport_unpack(struct gb_operation_msg_hdr *header)
 169 {
 170         u16 cport_id = header->pad[0];
 171
 172         gb_message_cport_clear(header);
 173
 174         return cport_id;
 175 }
 176
 177 /*
 178  * Returns zero if the message was successfully queued, or a negative errno
 179  * otherwise.
 180  */
 181 static int message_send(struct greybus_host_device *hd, u16 cport_id,
 182                         struct gb_message *message, gfp_t gfp_mask)
 183 {
 184         struct es1_ap_dev *es1 = hd_to_es1(hd);
 185         struct usb_device *udev = es1->usb_dev;
 186         size_t buffer_size;
 187         int retval;
 188         struct urb *urb;
 189         unsigned long flags;
 190
 191         /*
 192          * The data actually transferred will include an indication
 193          * of where the data should be sent.  Do one last check of
 194          * the target CPort id before filling it in.
 195          */
 196         if (!cport_id_valid(cport_id)) {
 197                 pr_err("invalid destination cport 0x%02x\n", cport_id);
 198                 return -EINVAL;
 199         }
 200
 201         /* Find a free urb */
 202         urb = next_free_urb(es1, gfp_mask);
 203         if (!urb)
 204                 return -ENOMEM;
 205
 206         spin_lock_irqsave(&es1->cport_out_urb_lock, flags);
 207         message->hcpriv = urb;
 208         spin_unlock_irqrestore(&es1->cport_out_urb_lock, flags);
 209
 210         /* Pack the cport id into the message header */
 211         gb_message_cport_pack(message->header, cport_id);
 212
 213         buffer_size = sizeof(*message->header) + message->payload_size;
 214
 215         usb_fill_bulk_urb(urb, udev,
 216                           usb_sndbulkpipe(udev, es1->cport_out_endpoint),
 217                           message->buffer, buffer_size,
 218                           cport_out_callback, message);
 219         gb_connection_push_timestamp(message->operation->connection);
 220         retval = usb_submit_urb(urb, gfp_mask);
 221         if (retval) {
 222                 pr_err("error %d submitting URB\n", retval);
 223
 224                 spin_lock_irqsave(&es1->cport_out_urb_lock, flags);
 225                 message->hcpriv = NULL;
 226                 spin_unlock_irqrestore(&es1->cport_out_urb_lock, flags);
 227
 228                 free_urb(es1, urb);
 229                 gb_message_cport_clear(message->header);
 230
 231                 return retval;
 232         }
 233
 234         return 0;
 235 }
 236
 237 /*
 238  * Can not be called in atomic context.
 239  */
 240 static void message_cancel(struct gb_message *message)
 241 {
 242         struct greybus_host_device *hd = message->operation->connection->hd;
 243         struct es1_ap_dev *es1 = hd_to_es1(hd);
 244         struct urb *urb;
 245         int i;
 246
 247         might_sleep();
 248
 249         spin_lock_irq(&es1->cport_out_urb_lock);
 250         urb = message->hcpriv;
 251
 252         /* Prevent dynamically allocated urb from being deallocated. */
 253         usb_get_urb(urb);
 254
 255         /* Prevent pre-allocated urb from being reused. */
 256         for (i = 0; i < NUM_CPORT_OUT_URB; ++i) {
 257                 if (urb == es1->cport_out_urb[i]) {
 258                         es1->cport_out_urb_cancelled[i] = true;
 259                         break;
 260                 }
 261         }
 262         spin_unlock_irq(&es1->cport_out_urb_lock);
 263
 264         usb_kill_urb(urb);
 265
 266         if (i < NUM_CPORT_OUT_URB) {
 267                 spin_lock_irq(&es1->cport_out_urb_lock);
 268                 es1->cport_out_urb_cancelled[i] = false;
 269                 spin_unlock_irq(&es1->cport_out_urb_lock);
 270         }
 271
 272         usb_free_urb(urb);
 273 }
 274
 275 static struct greybus_host_driver es1_driver = {
 276         .hd_priv_size           = sizeof(struct es1_ap_dev),
 277         .message_send           = message_send,
 278         .message_cancel         = message_cancel,
 279 };
 280
 281 /* Common function to report consistent warnings based on URB status */
 282 static int check_urb_status(struct urb *urb)
 283 {
 284         struct device *dev = &urb->dev->dev;
 285         int status = urb->status;
 286
 287         switch (status) {
 288         case 0:
 289                 return 0;
 290
 291         case -EOVERFLOW:
 292                 dev_err(dev, "%s: overflow actual length is %d\n",
 293                         __func__, urb->actual_length);
 294         case -ECONNRESET:
 295         case -ENOENT:
 296         case -ESHUTDOWN:
 297         case -EILSEQ:
 298         case -EPROTO:
 299                 /* device is gone, stop sending */
 300                 return status;
 301         }
 302         dev_err(dev, "%s: unknown status %d\n", __func__, status);
 303
 304         return -EAGAIN;
 305 }
 306
 307 static void ap_disconnect(struct usb_interface *interface)
 308 {
 309         struct es1_ap_dev *es1;
 310         struct usb_device *udev;
 311         int i;
 312
 313         es1 = usb_get_intfdata(interface);
 314         if (!es1)
 315                 return;
 316
 317         usb_log_disable(es1);
 318
 319         /* Tear down everything! */
 320         for (i = 0; i < NUM_CPORT_OUT_URB; ++i) {
 321                 struct urb *urb = es1->cport_out_urb[i];
 322
 323                 if (!urb)
 324                         break;
 325                 usb_kill_urb(urb);
 326                 usb_free_urb(urb);
 327                 es1->cport_out_urb[i] = NULL;
 328                 es1->cport_out_urb_busy[i] = false;     /* just to be anal */
 329         }
 330
 331         for (i = 0; i < NUM_CPORT_IN_URB; ++i) {
 332                 struct urb *urb = es1->cport_in_urb[i];
 333
 334                 if (!urb)
 335                         break;
 336                 usb_kill_urb(urb);
 337                 usb_free_urb(urb);
 338                 kfree(es1->cport_in_buffer[i]);
 339                 es1->cport_in_buffer[i] = NULL;
 340         }
 341
 342         usb_set_intfdata(interface, NULL);
 343         udev = es1->usb_dev;
 344         greybus_remove_hd(es1->hd);
 345
 346         usb_put_dev(udev);
 347 }
 348
 349 static void cport_in_callback(struct urb *urb)
 350 {
 351         struct greybus_host_device *hd = urb->context;
 352         struct device *dev = &urb->dev->dev;
 353         struct gb_operation_msg_hdr *header;
 354         int status = check_urb_status(urb);
 355         int retval;
 356         u16 cport_id;
 357
 358         if (status) {
 359                 if ((status == -EAGAIN) || (status == -EPROTO))
 360                         goto exit;
 361                 dev_err(dev, "urb cport in error %d (dropped)\n", status);
 362                 return;
 363         }
 364
 365         if (urb->actual_length < sizeof(*header)) {
 366                 dev_err(dev, "%s: short message received\n", __func__);
 367                 goto exit;
 368         }
 369
 370         /* Extract the CPort id, which is packed in the message header */
 371         header = urb->transfer_buffer;
 372         cport_id = gb_message_cport_unpack(header);
 373
 374         if (cport_id_valid(cport_id))
 375                 greybus_data_rcvd(hd, cport_id, urb->transfer_buffer,
 376                                                         urb->actual_length);
 377         else
 378                 dev_err(dev, "%s: invalid cport id 0x%02x received\n",
 379                                 __func__, cport_id);
 380 exit:
 381         /* put our urb back in the request pool */
 382         retval = usb_submit_urb(urb, GFP_ATOMIC);
 383         if (retval)
 384                 dev_err(dev, "%s: error %d in submitting urb.\n",
 385                         __func__, retval);
 386 }
 387
 388 static void cport_out_callback(struct urb *urb)
 389 {
 390         struct gb_message *message = urb->context;
 391         struct greybus_host_device *hd = message->operation->connection->hd;
 392         struct es1_ap_dev *es1 = hd_to_es1(hd);
 393         int status = check_urb_status(urb);
 394         unsigned long flags;
 395
 396         gb_message_cport_clear(message->header);
 397
 398         /*
 399          * Tell the submitter that the message send (attempt) is
 400          * complete, and report the status.
 401          */
 402         greybus_message_sent(hd, message, status);
 403
 404         spin_lock_irqsave(&es1->cport_out_urb_lock, flags);
 405         message->hcpriv = NULL;
 406         spin_unlock_irqrestore(&es1->cport_out_urb_lock, flags);
 407
 408         free_urb(es1, urb);
 409 }
 410
 411 #define APB1_LOG_MSG_SIZE       64
 412 static void apb1_log_get(struct es1_ap_dev *es1, char *buf)
 413 {
 414         int retval;
 415
 416         /* SVC messages go down our control pipe */
 417         do {
 418                 retval = usb_control_msg(es1->usb_dev,
 419                                         usb_rcvctrlpipe(es1->usb_dev,
 420                                                         es1->control_endpoint),
 421                                         REQUEST_LOG,
 422                                         USB_DIR_IN | USB_TYPE_VENDOR | USB_RECIP_INTERFACE,
 423                                         0x00, 0x00,
 424                                         buf,
 425                                         APB1_LOG_MSG_SIZE,
 426                                         ES1_TIMEOUT);
 427                 if (retval > 0)
 428                         kfifo_in(&apb1_log_fifo, buf, retval);
 429         } while (retval > 0);
 430 }
 431
 432 static int apb1_log_poll(void *data)
 433 {
 434         struct es1_ap_dev *es1 = data;
 435         char *buf;
 436
 437         buf = kmalloc(APB1_LOG_MSG_SIZE, GFP_KERNEL);
 438         if (!buf)
 439                 return -ENOMEM;
 440
 441         while (!kthread_should_stop()) {
 442                 msleep(1000);
 443                 apb1_log_get(es1, buf);
 444         }
 445
 446         kfree(buf);
 447
 448         return 0;
 449 }
 450
 451 static ssize_t apb1_log_read(struct file *f, char __user *buf,
 452                                 size_t count, loff_t *ppos)
 453 {
 454         ssize_t ret;
 455         size_t copied;
 456         char *tmp_buf;
 457
 458         if (count > APB1_LOG_SIZE)
 459                 count = APB1_LOG_SIZE;
 460
 461         tmp_buf = kmalloc(count, GFP_KERNEL);
 462         if (!tmp_buf)
 463                 return -ENOMEM;
 464
 465         copied = kfifo_out(&apb1_log_fifo, tmp_buf, count);
 466         ret = simple_read_from_buffer(buf, count, ppos, tmp_buf, copied);
 467
 468         kfree(tmp_buf);
 469
 470         return ret;
 471 }
 472
 473 static const struct file_operations apb1_log_fops = {
 474         .read   = apb1_log_read,
 475 };
 476
 477 static void usb_log_enable(struct es1_ap_dev *es1)
 478 {
 479         if (!IS_ERR_OR_NULL(apb1_log_task))
 480                 return;
 481
 482         /* get log from APB1 */
 483         apb1_log_task = kthread_run(apb1_log_poll, es1, "apb1_log");
 484         if (IS_ERR(apb1_log_task))
 485                 return;
 486         apb1_log_dentry = debugfs_create_file("apb1_log", S_IRUGO,
 487                                                 gb_debugfs_get(), NULL,
 488                                                 &apb1_log_fops);
 489 }
 490
 491 static void usb_log_disable(struct es1_ap_dev *es1)
 492 {
 493         if (IS_ERR_OR_NULL(apb1_log_task))
 494                 return;
 495
 496         debugfs_remove(apb1_log_dentry);
 497         apb1_log_dentry = NULL;
 498
 499         kthread_stop(apb1_log_task);
 500         apb1_log_task = NULL;
 501 }
 502
 503 static ssize_t apb1_log_enable_read(struct file *f, char __user *buf,
 504                                 size_t count, loff_t *ppos)
 505 {
 506         char tmp_buf[3];
 507         int enable = !IS_ERR_OR_NULL(apb1_log_task);
 508
 509         sprintf(tmp_buf, "%d\n", enable);
 510         return simple_read_from_buffer(buf, count, ppos, tmp_buf, 3);
 511 }
 512
 513 static ssize_t apb1_log_enable_write(struct file *f, const char __user *buf,
 514                                 size_t count, loff_t *ppos)
 515 {
 516         int enable;
 517         ssize_t retval;
 518         struct es1_ap_dev *es1 = (struct es1_ap_dev *)f->f_inode->i_private;
 519
 520         retval = kstrtoint_from_user(buf, count, 10, &enable);
 521         if (retval)
 522                 return retval;
 523
 524         if (enable)
 525                 usb_log_enable(es1);
 526         else
 527                 usb_log_disable(es1);
 528
 529         return count;
 530 }
 531
 532 static const struct file_operations apb1_log_enable_fops = {
 533         .read   = apb1_log_enable_read,
 534         .write  = apb1_log_enable_write,
 535 };
 536
 537 /*
 538  * The ES1 USB Bridge device contains 4 endpoints
 539  * 1 Control - usual USB stuff + AP -> SVC messages
 540  * 1 Interrupt IN - SVC -> AP messages
 541  * 1 Bulk IN - CPort data in
 542  * 1 Bulk OUT - CPort data out
 543  */
 544 static int ap_probe(struct usb_interface *interface,
 545                     const struct usb_device_id *id)
 546 {
 547         struct es1_ap_dev *es1;
 548         struct greybus_host_device *hd;
 549         struct usb_device *udev;
 550         struct usb_host_interface *iface_desc;
 551         struct usb_endpoint_descriptor *endpoint;
 552         bool bulk_in_found = false;
 553         bool bulk_out_found = false;
 554         int retval = -ENOMEM;
 555         int i;
 556
 557         /* We need to fit a CPort ID in one byte of a message header */
 558         BUILD_BUG_ON(CPORT_ID_MAX > U8_MAX);
 559
 560         udev = usb_get_dev(interface_to_usbdev(interface));
 561
 562         hd = greybus_create_hd(&es1_driver, &udev->dev, ES1_GBUF_MSG_SIZE_MAX);
 563         if (IS_ERR(hd)) {
 564                 usb_put_dev(udev);
 565                 return PTR_ERR(hd);
 566         }
 567
 568         es1 = hd_to_es1(hd);
 569         es1->hd = hd;
 570         es1->usb_intf = interface;
 571         es1->usb_dev = udev;
 572         spin_lock_init(&es1->cport_out_urb_lock);
 573         usb_set_intfdata(interface, es1);
 574
 575         /* Control endpoint is the pipe to talk to this AP, so save it off */
 576         endpoint = &udev->ep0.desc;
 577         es1->control_endpoint = endpoint->bEndpointAddress;
 578
 579         /* find all 3 of our endpoints */
 580         iface_desc = interface->cur_altsetting;
 581         for (i = 0; i < iface_desc->desc.bNumEndpoints; ++i) {
 582                 endpoint = &iface_desc->endpoint[i].desc;
 583
 584                 if (usb_endpoint_is_bulk_in(endpoint)) {
 585                         es1->cport_in_endpoint = endpoint->bEndpointAddress;
 586                         bulk_in_found = true;
 587                 } else if (usb_endpoint_is_bulk_out(endpoint)) {
 588                         es1->cport_out_endpoint = endpoint->bEndpointAddress;
 589                         bulk_out_found = true;
 590                 } else {
 591                         dev_err(&udev->dev,
 592                                 "Unknown endpoint type found, address %x\n",
 593                                 endpoint->bEndpointAddress);
 594                 }
 595         }
 596         if ((bulk_in_found == false) ||
 597             (bulk_out_found == false)) {
 598                 dev_err(&udev->dev, "Not enough endpoints found in device, aborting!\n");
 599                 goto error;
 600         }
 601
 602         /* Allocate buffers for our cport in messages and start them up */
 603         for (i = 0; i < NUM_CPORT_IN_URB; ++i) {
 604                 struct urb *urb;
 605                 u8 *buffer;
 606
 607                 urb = usb_alloc_urb(0, GFP_KERNEL);
 608                 if (!urb)
 609                         goto error;
 610                 buffer = kmalloc(ES1_GBUF_MSG_SIZE_MAX, GFP_KERNEL);
 611                 if (!buffer)
 612                         goto error;
 613
 614                 usb_fill_bulk_urb(urb, udev,
 615                                   usb_rcvbulkpipe(udev, es1->cport_in_endpoint),
 616                                   buffer, ES1_GBUF_MSG_SIZE_MAX,
 617                                   cport_in_callback, hd);
 618                 es1->cport_in_urb[i] = urb;
 619                 es1->cport_in_buffer[i] = buffer;
 620                 retval = usb_submit_urb(urb, GFP_KERNEL);
 621                 if (retval)
 622                         goto error;
 623         }
 624
 625         /* Allocate urbs for our CPort OUT messages */
 626         for (i = 0; i < NUM_CPORT_OUT_URB; ++i) {
 627                 struct urb *urb;
 628
 629                 urb = usb_alloc_urb(0, GFP_KERNEL);
 630                 if (!urb)
 631                         goto error;
 632
 633                 es1->cport_out_urb[i] = urb;
 634                 es1->cport_out_urb_busy[i] = false;     /* just to be anal */
 635         }
 636
 637         apb1_log_enable_dentry = debugfs_create_file("apb1_log_enable",
 638                                                         (S_IWUSR | S_IRUGO),
 639                                                         gb_debugfs_get(), es1,
 640                                                         &apb1_log_enable_fops);
 641         return 0;
 642 error:
 643         ap_disconnect(interface);
 644
 645         return retval;
 646 }
 647
 648 static struct usb_driver es1_ap_driver = {
 649         .name =         "es1_ap_driver",
 650         .probe =        ap_probe,
 651         .disconnect =   ap_disconnect,
 652         .id_table =     id_table,
 653 };
 654
 655 module_usb_driver(es1_ap_driver);
 656
 657 MODULE_LICENSE("GPL v2");
 658 MODULE_AUTHOR("Greg Kroah-Hartman <gregkh@linuxfoundation.org>");