1 /* 2 * spidev.c -- simple synchronous userspace interface to SPI devices 3 * 4 * Copyright (C) 2006 SWAPP 5 * Andrea Paterniani <a.paterniani@swapp-eng.it> 6 * Copyright (C) 2007 David Brownell (simplification, cleanup) 7 * 8 * This program is free software; you can redistribute it and/or modify 9 * it under the terms of the GNU General Public License as published by 10 * the Free Software Foundation; either version 2 of the License, or 11 * (at your option) any later version. 12 * 13 * This program is distributed in the hope that it will be useful, 14 * but WITHOUT ANY WARRANTY; without even the implied warranty of 15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 16 * GNU General Public License for more details. 17 * 18 * You should have received a copy of the GNU General Public License 19 * along with this program; if not, write to the Free Software 20 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. 21 */ 22 23 #include <linux/init.h> 24 #include <linux/module.h> 25 #include <linux/ioctl.h> 26 #include <linux/fs.h> 27 #include <linux/device.h> 28 #include <linux/err.h> 29 #include <linux/list.h> 30 #include <linux/errno.h> 31 #include <linux/mutex.h> 32 #include <linux/slab.h> 33 34 #include <linux/spi/spi.h> 35 #include <linux/spi/spidev.h> 36 37 #include <asm/uaccess.h> 38 39 40 /* 41 * This supports acccess to SPI devices using normal userspace I/O calls. 42 * Note that while traditional UNIX/POSIX I/O semantics are half duplex, 43 * and often mask message boundaries, full SPI support requires full duplex 44 * transfers. There are several kinds of internal message boundaries to 45 * handle chipselect management and other protocol options. 46 * 47 * SPI has a character major number assigned. We allocate minor numbers 48 * dynamically using a bitmask. You must use hotplug tools, such as udev 49 * (or mdev with busybox) to create and destroy the /dev/spidevB.C device 50 * nodes, since there is no fixed association of minor numbers with any 51 * particular SPI bus or device. 52 */ 53 #define SPIDEV_MAJOR 153 /* assigned */ 54 #define N_SPI_MINORS 32 /* ... up to 256 */ 55 56 static DECLARE_BITMAP(minors, N_SPI_MINORS); 57 58 59 /* Bit masks for spi_device.mode management. Note that incorrect 60 * settings for some settings can cause *lots* of trouble for other 61 * devices on a shared bus: 62 * 63 * - CS_HIGH ... this device will be active when it shouldn't be 64 * - 3WIRE ... when active, it won't behave as it should 65 * - NO_CS ... there will be no explicit message boundaries; this 66 * is completely incompatible with the shared bus model 67 * - READY ... transfers may proceed when they shouldn't. 68 * 69 * REVISIT should changing those flags be privileged? 70 */ 71 #define SPI_MODE_MASK (SPI_CPHA | SPI_CPOL | SPI_CS_HIGH \ 72 | SPI_LSB_FIRST | SPI_3WIRE | SPI_LOOP \ 73 | SPI_NO_CS | SPI_READY) 74 75 struct spidev_data { 76 dev_t devt; 77 spinlock_t spi_lock; 78 struct spi_device *spi; 79 struct list_head device_entry; 80 81 /* buffer is NULL unless this device is open (users > 0) */ 82 struct mutex buf_lock; 83 unsigned users; 84 u8 *buffer; 85 }; 86 87 static LIST_HEAD(device_list); 88 static DEFINE_MUTEX(device_list_lock); 89 90 static unsigned bufsiz = 4096; 91 module_param(bufsiz, uint, S_IRUGO); 92 MODULE_PARM_DESC(bufsiz, "data bytes in biggest supported SPI message"); 93 94 /*-------------------------------------------------------------------------*/ 95 96 /* 97 * We can't use the standard synchronous wrappers for file I/O; we 98 * need to protect against async removal of the underlying spi_device. 99 */ 100 static void spidev_complete(void *arg) 101 { 102 complete(arg); 103 } 104 105 static ssize_t 106 spidev_sync(struct spidev_data *spidev, struct spi_message *message) 107 { 108 DECLARE_COMPLETION_ONSTACK(done); 109 int status; 110 111 message->complete = spidev_complete; 112 message->context = &done; 113 114 spin_lock_irq(&spidev->spi_lock); 115 if (spidev->spi == NULL) 116 status = -ESHUTDOWN; 117 else 118 status = spi_async(spidev->spi, message); 119 spin_unlock_irq(&spidev->spi_lock); 120 121 if (status == 0) { 122 wait_for_completion(&done); 123 status = message->status; 124 if (status == 0) 125 status = message->actual_length; 126 } 127 return status; 128 } 129 130 static inline ssize_t 131 spidev_sync_write(struct spidev_data *spidev, size_t len) 132 { 133 struct spi_transfer t = { 134 .tx_buf = spidev->buffer, 135 .len = len, 136 }; 137 struct spi_message m; 138 139 spi_message_init(&m); 140 spi_message_add_tail(&t, &m); 141 return spidev_sync(spidev, &m); 142 } 143 144 static inline ssize_t 145 spidev_sync_read(struct spidev_data *spidev, size_t len) 146 { 147 struct spi_transfer t = { 148 .rx_buf = spidev->buffer, 149 .len = len, 150 }; 151 struct spi_message m; 152 153 spi_message_init(&m); 154 spi_message_add_tail(&t, &m); 155 return spidev_sync(spidev, &m); 156 } 157 158 /*-------------------------------------------------------------------------*/ 159 160 /* Read-only message with current device setup */ 161 static ssize_t 162 spidev_read(struct file *filp, char __user *buf, size_t count, loff_t *f_pos) 163 { 164 struct spidev_data *spidev; 165 ssize_t status = 0; 166 167 /* chipselect only toggles at start or end of operation */ 168 if (count > bufsiz) 169 return -EMSGSIZE; 170 171 spidev = filp->private_data; 172 173 mutex_lock(&spidev->buf_lock); 174 status = spidev_sync_read(spidev, count); 175 if (status > 0) { 176 unsigned long missing; 177 178 missing = copy_to_user(buf, spidev->buffer, status); 179 if (missing == status) 180 status = -EFAULT; 181 else 182 status = status - missing; 183 } 184 mutex_unlock(&spidev->buf_lock); 185 186 return status; 187 } 188 189 /* Write-only message with current device setup */ 190 static ssize_t 191 spidev_write(struct file *filp, const char __user *buf, 192 size_t count, loff_t *f_pos) 193 { 194 struct spidev_data *spidev; 195 ssize_t status = 0; 196 unsigned long missing; 197 198 /* chipselect only toggles at start or end of operation */ 199 if (count > bufsiz) 200 return -EMSGSIZE; 201 202 spidev = filp->private_data; 203 204 mutex_lock(&spidev->buf_lock); 205 missing = copy_from_user(spidev->buffer, buf, count); 206 if (missing == 0) { 207 status = spidev_sync_write(spidev, count); 208 } else 209 status = -EFAULT; 210 mutex_unlock(&spidev->buf_lock); 211 212 return status; 213 } 214 215 static int spidev_message(struct spidev_data *spidev, 216 struct spi_ioc_transfer *u_xfers, unsigned n_xfers) 217 { 218 struct spi_message msg; 219 struct spi_transfer *k_xfers; 220 struct spi_transfer *k_tmp; 221 struct spi_ioc_transfer *u_tmp; 222 unsigned n, total; 223 u8 *buf; 224 int status = -EFAULT; 225 226 spi_message_init(&msg); 227 k_xfers = kcalloc(n_xfers, sizeof(*k_tmp), GFP_KERNEL); 228 if (k_xfers == NULL) 229 return -ENOMEM; 230 231 /* Construct spi_message, copying any tx data to bounce buffer. 232 * We walk the array of user-provided transfers, using each one 233 * to initialize a kernel version of the same transfer. 234 */ 235 buf = spidev->buffer; 236 total = 0; 237 for (n = n_xfers, k_tmp = k_xfers, u_tmp = u_xfers; 238 n; 239 n--, k_tmp++, u_tmp++) { 240 k_tmp->len = u_tmp->len; 241 242 total += k_tmp->len; 243 if (total > bufsiz) { 244 status = -EMSGSIZE; 245 goto done; 246 } 247 248 if (u_tmp->rx_buf) { 249 k_tmp->rx_buf = buf; 250 if (!access_ok(VERIFY_WRITE, (u8 __user *) 251 (uintptr_t) u_tmp->rx_buf, 252 u_tmp->len)) 253 goto done; 254 } 255 if (u_tmp->tx_buf) { 256 k_tmp->tx_buf = buf; 257 if (copy_from_user(buf, (const u8 __user *) 258 (uintptr_t) u_tmp->tx_buf, 259 u_tmp->len)) 260 goto done; 261 } 262 buf += k_tmp->len; 263 264 k_tmp->cs_change = !!u_tmp->cs_change; 265 k_tmp->bits_per_word = u_tmp->bits_per_word; 266 k_tmp->delay_usecs = u_tmp->delay_usecs; 267 k_tmp->speed_hz = u_tmp->speed_hz; 268 #ifdef VERBOSE 269 dev_dbg(&spidev->spi->dev, 270 " xfer len %zd %s%s%s%dbits %u usec %uHz\n", 271 u_tmp->len, 272 u_tmp->rx_buf ? "rx " : "", 273 u_tmp->tx_buf ? "tx " : "", 274 u_tmp->cs_change ? "cs " : "", 275 u_tmp->bits_per_word ? : spidev->spi->bits_per_word, 276 u_tmp->delay_usecs, 277 u_tmp->speed_hz ? : spidev->spi->max_speed_hz); 278 #endif 279 spi_message_add_tail(k_tmp, &msg); 280 } 281 282 status = spidev_sync(spidev, &msg); 283 if (status < 0) 284 goto done; 285 286 /* copy any rx data out of bounce buffer */ 287 buf = spidev->buffer; 288 for (n = n_xfers, u_tmp = u_xfers; n; n--, u_tmp++) { 289 if (u_tmp->rx_buf) { 290 if (__copy_to_user((u8 __user *) 291 (uintptr_t) u_tmp->rx_buf, buf, 292 u_tmp->len)) { 293 status = -EFAULT; 294 goto done; 295 } 296 } 297 buf += u_tmp->len; 298 } 299 status = total; 300 301 done: 302 kfree(k_xfers); 303 return status; 304 } 305 306 static long 307 spidev_ioctl(struct file *filp, unsigned int cmd, unsigned long arg) 308 { 309 int err = 0; 310 int retval = 0; 311 struct spidev_data *spidev; 312 struct spi_device *spi; 313 u32 tmp; 314 unsigned n_ioc; 315 struct spi_ioc_transfer *ioc; 316 317 /* Check type and command number */ 318 if (_IOC_TYPE(cmd) != SPI_IOC_MAGIC) 319 return -ENOTTY; 320 321 /* Check access direction once here; don't repeat below. 322 * IOC_DIR is from the user perspective, while access_ok is 323 * from the kernel perspective; so they look reversed. 324 */ 325 if (_IOC_DIR(cmd) & _IOC_READ) 326 err = !access_ok(VERIFY_WRITE, 327 (void __user *)arg, _IOC_SIZE(cmd)); 328 if (err == 0 && _IOC_DIR(cmd) & _IOC_WRITE) 329 err = !access_ok(VERIFY_READ, 330 (void __user *)arg, _IOC_SIZE(cmd)); 331 if (err) 332 return -EFAULT; 333 334 /* guard against device removal before, or while, 335 * we issue this ioctl. 336 */ 337 spidev = filp->private_data; 338 spin_lock_irq(&spidev->spi_lock); 339 spi = spi_dev_get(spidev->spi); 340 spin_unlock_irq(&spidev->spi_lock); 341 342 if (spi == NULL) 343 return -ESHUTDOWN; 344 345 /* use the buffer lock here for triple duty: 346 * - prevent I/O (from us) so calling spi_setup() is safe; 347 * - prevent concurrent SPI_IOC_WR_* from morphing 348 * data fields while SPI_IOC_RD_* reads them; 349 * - SPI_IOC_MESSAGE needs the buffer locked "normally". 350 */ 351 mutex_lock(&spidev->buf_lock); 352 353 switch (cmd) { 354 /* read requests */ 355 case SPI_IOC_RD_MODE: 356 retval = __put_user(spi->mode & SPI_MODE_MASK, 357 (__u8 __user *)arg); 358 break; 359 case SPI_IOC_RD_LSB_FIRST: 360 retval = __put_user((spi->mode & SPI_LSB_FIRST) ? 1 : 0, 361 (__u8 __user *)arg); 362 break; 363 case SPI_IOC_RD_BITS_PER_WORD: 364 retval = __put_user(spi->bits_per_word, (__u8 __user *)arg); 365 break; 366 case SPI_IOC_RD_MAX_SPEED_HZ: 367 retval = __put_user(spi->max_speed_hz, (__u32 __user *)arg); 368 break; 369 370 /* write requests */ 371 case SPI_IOC_WR_MODE: 372 retval = __get_user(tmp, (u8 __user *)arg); 373 if (retval == 0) { 374 u8 save = spi->mode; 375 376 if (tmp & ~SPI_MODE_MASK) { 377 retval = -EINVAL; 378 break; 379 } 380 381 tmp |= spi->mode & ~SPI_MODE_MASK; 382 spi->mode = (u8)tmp; 383 retval = spi_setup(spi); 384 if (retval < 0) 385 spi->mode = save; 386 else 387 dev_dbg(&spi->dev, "spi mode %02x\n", tmp); 388 } 389 break; 390 case SPI_IOC_WR_LSB_FIRST: 391 retval = __get_user(tmp, (__u8 __user *)arg); 392 if (retval == 0) { 393 u8 save = spi->mode; 394 395 if (tmp) 396 spi->mode |= SPI_LSB_FIRST; 397 else 398 spi->mode &= ~SPI_LSB_FIRST; 399 retval = spi_setup(spi); 400 if (retval < 0) 401 spi->mode = save; 402 else 403 dev_dbg(&spi->dev, "%csb first\n", 404 tmp ? 'l' : 'm'); 405 } 406 break; 407 case SPI_IOC_WR_BITS_PER_WORD: 408 retval = __get_user(tmp, (__u8 __user *)arg); 409 if (retval == 0) { 410 u8 save = spi->bits_per_word; 411 412 spi->bits_per_word = tmp; 413 retval = spi_setup(spi); 414 if (retval < 0) 415 spi->bits_per_word = save; 416 else 417 dev_dbg(&spi->dev, "%d bits per word\n", tmp); 418 } 419 break; 420 case SPI_IOC_WR_MAX_SPEED_HZ: 421 retval = __get_user(tmp, (__u32 __user *)arg); 422 if (retval == 0) { 423 u32 save = spi->max_speed_hz; 424 425 spi->max_speed_hz = tmp; 426 retval = spi_setup(spi); 427 if (retval < 0) 428 spi->max_speed_hz = save; 429 else 430 dev_dbg(&spi->dev, "%d Hz (max)\n", tmp); 431 } 432 break; 433 434 default: 435 /* segmented and/or full-duplex I/O request */ 436 if (_IOC_NR(cmd) != _IOC_NR(SPI_IOC_MESSAGE(0)) 437 || _IOC_DIR(cmd) != _IOC_WRITE) { 438 retval = -ENOTTY; 439 break; 440 } 441 442 tmp = _IOC_SIZE(cmd); 443 if ((tmp % sizeof(struct spi_ioc_transfer)) != 0) { 444 retval = -EINVAL; 445 break; 446 } 447 n_ioc = tmp / sizeof(struct spi_ioc_transfer); 448 if (n_ioc == 0) 449 break; 450 451 /* copy into scratch area */ 452 ioc = kmalloc(tmp, GFP_KERNEL); 453 if (!ioc) { 454 retval = -ENOMEM; 455 break; 456 } 457 if (__copy_from_user(ioc, (void __user *)arg, tmp)) { 458 kfree(ioc); 459 retval = -EFAULT; 460 break; 461 } 462 463 /* translate to spi_message, execute */ 464 retval = spidev_message(spidev, ioc, n_ioc); 465 kfree(ioc); 466 break; 467 } 468 469 mutex_unlock(&spidev->buf_lock); 470 spi_dev_put(spi); 471 return retval; 472 } 473 474 static int spidev_open(struct inode *inode, struct file *filp) 475 { 476 struct spidev_data *spidev; 477 int status = -ENXIO; 478 479 mutex_lock(&device_list_lock); 480 481 list_for_each_entry(spidev, &device_list, device_entry) { 482 if (spidev->devt == inode->i_rdev) { 483 status = 0; 484 break; 485 } 486 } 487 if (status == 0) { 488 if (!spidev->buffer) { 489 spidev->buffer = kmalloc(bufsiz, GFP_KERNEL); 490 if (!spidev->buffer) { 491 dev_dbg(&spidev->spi->dev, "open/ENOMEM\n"); 492 status = -ENOMEM; 493 } 494 } 495 if (status == 0) { 496 spidev->users++; 497 filp->private_data = spidev; 498 nonseekable_open(inode, filp); 499 } 500 } else 501 pr_debug("spidev: nothing for minor %d\n", iminor(inode)); 502 503 mutex_unlock(&device_list_lock); 504 return status; 505 } 506 507 static int spidev_release(struct inode *inode, struct file *filp) 508 { 509 struct spidev_data *spidev; 510 int status = 0; 511 512 mutex_lock(&device_list_lock); 513 spidev = filp->private_data; 514 filp->private_data = NULL; 515 516 /* last close? */ 517 spidev->users--; 518 if (!spidev->users) { 519 int dofree; 520 521 kfree(spidev->buffer); 522 spidev->buffer = NULL; 523 524 /* ... after we unbound from the underlying device? */ 525 spin_lock_irq(&spidev->spi_lock); 526 dofree = (spidev->spi == NULL); 527 spin_unlock_irq(&spidev->spi_lock); 528 529 if (dofree) 530 kfree(spidev); 531 } 532 mutex_unlock(&device_list_lock); 533 534 return status; 535 } 536 537 static const struct file_operations spidev_fops = { 538 .owner = THIS_MODULE, 539 /* REVISIT switch to aio primitives, so that userspace 540 * gets more complete API coverage. It'll simplify things 541 * too, except for the locking. 542 */ 543 .write = spidev_write, 544 .read = spidev_read, 545 .unlocked_ioctl = spidev_ioctl, 546 .open = spidev_open, 547 .release = spidev_release, 548 }; 549 550 /*-------------------------------------------------------------------------*/ 551 552 /* The main reason to have this class is to make mdev/udev create the 553 * /dev/spidevB.C character device nodes exposing our userspace API. 554 * It also simplifies memory management. 555 */ 556 557 static struct class *spidev_class; 558 559 /*-------------------------------------------------------------------------*/ 560 561 static int __devinit spidev_probe(struct spi_device *spi) 562 { 563 struct spidev_data *spidev; 564 int status; 565 unsigned long minor; 566 567 /* Allocate driver data */ 568 spidev = kzalloc(sizeof(*spidev), GFP_KERNEL); 569 if (!spidev) 570 return -ENOMEM; 571 572 /* Initialize the driver data */ 573 spidev->spi = spi; 574 spin_lock_init(&spidev->spi_lock); 575 mutex_init(&spidev->buf_lock); 576 577 INIT_LIST_HEAD(&spidev->device_entry); 578 579 /* If we can allocate a minor number, hook up this device. 580 * Reusing minors is fine so long as udev or mdev is working. 581 */ 582 mutex_lock(&device_list_lock); 583 minor = find_first_zero_bit(minors, N_SPI_MINORS); 584 if (minor < N_SPI_MINORS) { 585 struct device *dev; 586 587 spidev->devt = MKDEV(SPIDEV_MAJOR, minor); 588 dev = device_create(spidev_class, &spi->dev, spidev->devt, 589 spidev, "spidev%d.%d", 590 spi->master->bus_num, spi->chip_select); 591 status = IS_ERR(dev) ? PTR_ERR(dev) : 0; 592 } else { 593 dev_dbg(&spi->dev, "no minor number available!\n"); 594 status = -ENODEV; 595 } 596 if (status == 0) { 597 set_bit(minor, minors); 598 list_add(&spidev->device_entry, &device_list); 599 } 600 mutex_unlock(&device_list_lock); 601 602 if (status == 0) 603 spi_set_drvdata(spi, spidev); 604 else 605 kfree(spidev); 606 607 return status; 608 } 609 610 static int __devexit spidev_remove(struct spi_device *spi) 611 { 612 struct spidev_data *spidev = spi_get_drvdata(spi); 613 614 /* make sure ops on existing fds can abort cleanly */ 615 spin_lock_irq(&spidev->spi_lock); 616 spidev->spi = NULL; 617 spi_set_drvdata(spi, NULL); 618 spin_unlock_irq(&spidev->spi_lock); 619 620 /* prevent new opens */ 621 mutex_lock(&device_list_lock); 622 list_del(&spidev->device_entry); 623 device_destroy(spidev_class, spidev->devt); 624 clear_bit(MINOR(spidev->devt), minors); 625 if (spidev->users == 0) 626 kfree(spidev); 627 mutex_unlock(&device_list_lock); 628 629 return 0; 630 } 631 632 static struct spi_driver spidev_spi_driver = { 633 .driver = { 634 .name = "spidev", 635 .owner = THIS_MODULE, 636 }, 637 .probe = spidev_probe, 638 .remove = __devexit_p(spidev_remove), 639 640 /* NOTE: suspend/resume methods are not necessary here. 641 * We don't do anything except pass the requests to/from 642 * the underlying controller. The refrigerator handles 643 * most issues; the controller driver handles the rest. 644 */ 645 }; 646 647 /*-------------------------------------------------------------------------*/ 648 649 static int __init spidev_init(void) 650 { 651 int status; 652 653 /* Claim our 256 reserved device numbers. Then register a class 654 * that will key udev/mdev to add/remove /dev nodes. Last, register 655 * the driver which manages those device numbers. 656 */ 657 BUILD_BUG_ON(N_SPI_MINORS > 256); 658 status = register_chrdev(SPIDEV_MAJOR, "spi", &spidev_fops); 659 if (status < 0) 660 return status; 661 662 spidev_class = class_create(THIS_MODULE, "spidev"); 663 if (IS_ERR(spidev_class)) { 664 unregister_chrdev(SPIDEV_MAJOR, spidev_spi_driver.driver.name); 665 return PTR_ERR(spidev_class); 666 } 667 668 status = spi_register_driver(&spidev_spi_driver); 669 if (status < 0) { 670 class_destroy(spidev_class); 671 unregister_chrdev(SPIDEV_MAJOR, spidev_spi_driver.driver.name); 672 } 673 return status; 674 } 675 module_init(spidev_init); 676 677 static void __exit spidev_exit(void) 678 { 679 spi_unregister_driver(&spidev_spi_driver); 680 class_destroy(spidev_class); 681 unregister_chrdev(SPIDEV_MAJOR, spidev_spi_driver.driver.name); 682 } 683 module_exit(spidev_exit); 684 685 MODULE_AUTHOR("Andrea Paterniani, <a.paterniani@swapp-eng.it>"); 686 MODULE_DESCRIPTION("User mode SPI device interface"); 687 MODULE_LICENSE("GPL"); 688 MODULE_ALIAS("spi:spidev"); 689