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 #include <linux/compat.h> 34 35 #include <linux/spi/spi.h> 36 #include <linux/spi/spidev.h> 37 38 #include <asm/uaccess.h> 39 40 41 /* 42 * This supports access to SPI devices using normal userspace I/O calls. 43 * Note that while traditional UNIX/POSIX I/O semantics are half duplex, 44 * and often mask message boundaries, full SPI support requires full duplex 45 * transfers. There are several kinds of internal message boundaries to 46 * handle chipselect management and other protocol options. 47 * 48 * SPI has a character major number assigned. We allocate minor numbers 49 * dynamically using a bitmask. You must use hotplug tools, such as udev 50 * (or mdev with busybox) to create and destroy the /dev/spidevB.C device 51 * nodes, since there is no fixed association of minor numbers with any 52 * particular SPI bus or device. 53 */ 54 #define SPIDEV_MAJOR 153 /* assigned */ 55 #define N_SPI_MINORS 32 /* ... up to 256 */ 56 57 static DECLARE_BITMAP(minors, N_SPI_MINORS); 58 59 60 /* Bit masks for spi_device.mode management. Note that incorrect 61 * settings for some settings can cause *lots* of trouble for other 62 * devices on a shared bus: 63 * 64 * - CS_HIGH ... this device will be active when it shouldn't be 65 * - 3WIRE ... when active, it won't behave as it should 66 * - NO_CS ... there will be no explicit message boundaries; this 67 * is completely incompatible with the shared bus model 68 * - READY ... transfers may proceed when they shouldn't. 69 * 70 * REVISIT should changing those flags be privileged? 71 */ 72 #define SPI_MODE_MASK (SPI_CPHA | SPI_CPOL | SPI_CS_HIGH \ 73 | SPI_LSB_FIRST | SPI_3WIRE | SPI_LOOP \ 74 | SPI_NO_CS | SPI_READY) 75 76 struct spidev_data { 77 dev_t devt; 78 spinlock_t spi_lock; 79 struct spi_device *spi; 80 struct list_head device_entry; 81 82 /* buffer is NULL unless this device is open (users > 0) */ 83 struct mutex buf_lock; 84 unsigned users; 85 u8 *buffer; 86 }; 87 88 static LIST_HEAD(device_list); 89 static DEFINE_MUTEX(device_list_lock); 90 91 static unsigned bufsiz = 4096; 92 module_param(bufsiz, uint, S_IRUGO); 93 MODULE_PARM_DESC(bufsiz, "data bytes in biggest supported SPI message"); 94 95 /*-------------------------------------------------------------------------*/ 96 97 /* 98 * We can't use the standard synchronous wrappers for file I/O; we 99 * need to protect against async removal of the underlying spi_device. 100 */ 101 static void spidev_complete(void *arg) 102 { 103 complete(arg); 104 } 105 106 static ssize_t 107 spidev_sync(struct spidev_data *spidev, struct spi_message *message) 108 { 109 DECLARE_COMPLETION_ONSTACK(done); 110 int status; 111 112 message->complete = spidev_complete; 113 message->context = &done; 114 115 spin_lock_irq(&spidev->spi_lock); 116 if (spidev->spi == NULL) 117 status = -ESHUTDOWN; 118 else 119 status = spi_async(spidev->spi, message); 120 spin_unlock_irq(&spidev->spi_lock); 121 122 if (status == 0) { 123 wait_for_completion(&done); 124 status = message->status; 125 if (status == 0) 126 status = message->actual_length; 127 } 128 return status; 129 } 130 131 static inline ssize_t 132 spidev_sync_write(struct spidev_data *spidev, size_t len) 133 { 134 struct spi_transfer t = { 135 .tx_buf = spidev->buffer, 136 .len = len, 137 }; 138 struct spi_message m; 139 140 spi_message_init(&m); 141 spi_message_add_tail(&t, &m); 142 return spidev_sync(spidev, &m); 143 } 144 145 static inline ssize_t 146 spidev_sync_read(struct spidev_data *spidev, size_t len) 147 { 148 struct spi_transfer t = { 149 .rx_buf = spidev->buffer, 150 .len = len, 151 }; 152 struct spi_message m; 153 154 spi_message_init(&m); 155 spi_message_add_tail(&t, &m); 156 return spidev_sync(spidev, &m); 157 } 158 159 /*-------------------------------------------------------------------------*/ 160 161 /* Read-only message with current device setup */ 162 static ssize_t 163 spidev_read(struct file *filp, char __user *buf, size_t count, loff_t *f_pos) 164 { 165 struct spidev_data *spidev; 166 ssize_t status = 0; 167 168 /* chipselect only toggles at start or end of operation */ 169 if (count > bufsiz) 170 return -EMSGSIZE; 171 172 spidev = filp->private_data; 173 174 mutex_lock(&spidev->buf_lock); 175 status = spidev_sync_read(spidev, count); 176 if (status > 0) { 177 unsigned long missing; 178 179 missing = copy_to_user(buf, spidev->buffer, status); 180 if (missing == status) 181 status = -EFAULT; 182 else 183 status = status - missing; 184 } 185 mutex_unlock(&spidev->buf_lock); 186 187 return status; 188 } 189 190 /* Write-only message with current device setup */ 191 static ssize_t 192 spidev_write(struct file *filp, const char __user *buf, 193 size_t count, loff_t *f_pos) 194 { 195 struct spidev_data *spidev; 196 ssize_t status = 0; 197 unsigned long missing; 198 199 /* chipselect only toggles at start or end of operation */ 200 if (count > bufsiz) 201 return -EMSGSIZE; 202 203 spidev = filp->private_data; 204 205 mutex_lock(&spidev->buf_lock); 206 missing = copy_from_user(spidev->buffer, buf, count); 207 if (missing == 0) { 208 status = spidev_sync_write(spidev, count); 209 } else 210 status = -EFAULT; 211 mutex_unlock(&spidev->buf_lock); 212 213 return status; 214 } 215 216 static int spidev_message(struct spidev_data *spidev, 217 struct spi_ioc_transfer *u_xfers, unsigned n_xfers) 218 { 219 struct spi_message msg; 220 struct spi_transfer *k_xfers; 221 struct spi_transfer *k_tmp; 222 struct spi_ioc_transfer *u_tmp; 223 unsigned n, total; 224 u8 *buf; 225 int status = -EFAULT; 226 227 spi_message_init(&msg); 228 k_xfers = kcalloc(n_xfers, sizeof(*k_tmp), GFP_KERNEL); 229 if (k_xfers == NULL) 230 return -ENOMEM; 231 232 /* Construct spi_message, copying any tx data to bounce buffer. 233 * We walk the array of user-provided transfers, using each one 234 * to initialize a kernel version of the same transfer. 235 */ 236 buf = spidev->buffer; 237 total = 0; 238 for (n = n_xfers, k_tmp = k_xfers, u_tmp = u_xfers; 239 n; 240 n--, k_tmp++, u_tmp++) { 241 k_tmp->len = u_tmp->len; 242 243 total += k_tmp->len; 244 if (total > bufsiz) { 245 status = -EMSGSIZE; 246 goto done; 247 } 248 249 if (u_tmp->rx_buf) { 250 k_tmp->rx_buf = buf; 251 if (!access_ok(VERIFY_WRITE, (u8 __user *) 252 (uintptr_t) u_tmp->rx_buf, 253 u_tmp->len)) 254 goto done; 255 } 256 if (u_tmp->tx_buf) { 257 k_tmp->tx_buf = buf; 258 if (copy_from_user(buf, (const u8 __user *) 259 (uintptr_t) u_tmp->tx_buf, 260 u_tmp->len)) 261 goto done; 262 } 263 buf += k_tmp->len; 264 265 k_tmp->cs_change = !!u_tmp->cs_change; 266 k_tmp->bits_per_word = u_tmp->bits_per_word; 267 k_tmp->delay_usecs = u_tmp->delay_usecs; 268 k_tmp->speed_hz = u_tmp->speed_hz; 269 #ifdef VERBOSE 270 dev_dbg(&spidev->spi->dev, 271 " xfer len %zd %s%s%s%dbits %u usec %uHz\n", 272 u_tmp->len, 273 u_tmp->rx_buf ? "rx " : "", 274 u_tmp->tx_buf ? "tx " : "", 275 u_tmp->cs_change ? "cs " : "", 276 u_tmp->bits_per_word ? : spidev->spi->bits_per_word, 277 u_tmp->delay_usecs, 278 u_tmp->speed_hz ? : spidev->spi->max_speed_hz); 279 #endif 280 spi_message_add_tail(k_tmp, &msg); 281 } 282 283 status = spidev_sync(spidev, &msg); 284 if (status < 0) 285 goto done; 286 287 /* copy any rx data out of bounce buffer */ 288 buf = spidev->buffer; 289 for (n = n_xfers, u_tmp = u_xfers; n; n--, u_tmp++) { 290 if (u_tmp->rx_buf) { 291 if (__copy_to_user((u8 __user *) 292 (uintptr_t) u_tmp->rx_buf, buf, 293 u_tmp->len)) { 294 status = -EFAULT; 295 goto done; 296 } 297 } 298 buf += u_tmp->len; 299 } 300 status = total; 301 302 done: 303 kfree(k_xfers); 304 return status; 305 } 306 307 static long 308 spidev_ioctl(struct file *filp, unsigned int cmd, unsigned long arg) 309 { 310 int err = 0; 311 int retval = 0; 312 struct spidev_data *spidev; 313 struct spi_device *spi; 314 u32 tmp; 315 unsigned n_ioc; 316 struct spi_ioc_transfer *ioc; 317 318 /* Check type and command number */ 319 if (_IOC_TYPE(cmd) != SPI_IOC_MAGIC) 320 return -ENOTTY; 321 322 /* Check access direction once here; don't repeat below. 323 * IOC_DIR is from the user perspective, while access_ok is 324 * from the kernel perspective; so they look reversed. 325 */ 326 if (_IOC_DIR(cmd) & _IOC_READ) 327 err = !access_ok(VERIFY_WRITE, 328 (void __user *)arg, _IOC_SIZE(cmd)); 329 if (err == 0 && _IOC_DIR(cmd) & _IOC_WRITE) 330 err = !access_ok(VERIFY_READ, 331 (void __user *)arg, _IOC_SIZE(cmd)); 332 if (err) 333 return -EFAULT; 334 335 /* guard against device removal before, or while, 336 * we issue this ioctl. 337 */ 338 spidev = filp->private_data; 339 spin_lock_irq(&spidev->spi_lock); 340 spi = spi_dev_get(spidev->spi); 341 spin_unlock_irq(&spidev->spi_lock); 342 343 if (spi == NULL) 344 return -ESHUTDOWN; 345 346 /* use the buffer lock here for triple duty: 347 * - prevent I/O (from us) so calling spi_setup() is safe; 348 * - prevent concurrent SPI_IOC_WR_* from morphing 349 * data fields while SPI_IOC_RD_* reads them; 350 * - SPI_IOC_MESSAGE needs the buffer locked "normally". 351 */ 352 mutex_lock(&spidev->buf_lock); 353 354 switch (cmd) { 355 /* read requests */ 356 case SPI_IOC_RD_MODE: 357 retval = __put_user(spi->mode & SPI_MODE_MASK, 358 (__u8 __user *)arg); 359 break; 360 case SPI_IOC_RD_LSB_FIRST: 361 retval = __put_user((spi->mode & SPI_LSB_FIRST) ? 1 : 0, 362 (__u8 __user *)arg); 363 break; 364 case SPI_IOC_RD_BITS_PER_WORD: 365 retval = __put_user(spi->bits_per_word, (__u8 __user *)arg); 366 break; 367 case SPI_IOC_RD_MAX_SPEED_HZ: 368 retval = __put_user(spi->max_speed_hz, (__u32 __user *)arg); 369 break; 370 371 /* write requests */ 372 case SPI_IOC_WR_MODE: 373 retval = __get_user(tmp, (u8 __user *)arg); 374 if (retval == 0) { 375 u8 save = spi->mode; 376 377 if (tmp & ~SPI_MODE_MASK) { 378 retval = -EINVAL; 379 break; 380 } 381 382 tmp |= spi->mode & ~SPI_MODE_MASK; 383 spi->mode = (u8)tmp; 384 retval = spi_setup(spi); 385 if (retval < 0) 386 spi->mode = save; 387 else 388 dev_dbg(&spi->dev, "spi mode %02x\n", tmp); 389 } 390 break; 391 case SPI_IOC_WR_LSB_FIRST: 392 retval = __get_user(tmp, (__u8 __user *)arg); 393 if (retval == 0) { 394 u8 save = spi->mode; 395 396 if (tmp) 397 spi->mode |= SPI_LSB_FIRST; 398 else 399 spi->mode &= ~SPI_LSB_FIRST; 400 retval = spi_setup(spi); 401 if (retval < 0) 402 spi->mode = save; 403 else 404 dev_dbg(&spi->dev, "%csb first\n", 405 tmp ? 'l' : 'm'); 406 } 407 break; 408 case SPI_IOC_WR_BITS_PER_WORD: 409 retval = __get_user(tmp, (__u8 __user *)arg); 410 if (retval == 0) { 411 u8 save = spi->bits_per_word; 412 413 spi->bits_per_word = tmp; 414 retval = spi_setup(spi); 415 if (retval < 0) 416 spi->bits_per_word = save; 417 else 418 dev_dbg(&spi->dev, "%d bits per word\n", tmp); 419 } 420 break; 421 case SPI_IOC_WR_MAX_SPEED_HZ: 422 retval = __get_user(tmp, (__u32 __user *)arg); 423 if (retval == 0) { 424 u32 save = spi->max_speed_hz; 425 426 spi->max_speed_hz = tmp; 427 retval = spi_setup(spi); 428 if (retval < 0) 429 spi->max_speed_hz = save; 430 else 431 dev_dbg(&spi->dev, "%d Hz (max)\n", tmp); 432 } 433 break; 434 435 default: 436 /* segmented and/or full-duplex I/O request */ 437 if (_IOC_NR(cmd) != _IOC_NR(SPI_IOC_MESSAGE(0)) 438 || _IOC_DIR(cmd) != _IOC_WRITE) { 439 retval = -ENOTTY; 440 break; 441 } 442 443 tmp = _IOC_SIZE(cmd); 444 if ((tmp % sizeof(struct spi_ioc_transfer)) != 0) { 445 retval = -EINVAL; 446 break; 447 } 448 n_ioc = tmp / sizeof(struct spi_ioc_transfer); 449 if (n_ioc == 0) 450 break; 451 452 /* copy into scratch area */ 453 ioc = kmalloc(tmp, GFP_KERNEL); 454 if (!ioc) { 455 retval = -ENOMEM; 456 break; 457 } 458 if (__copy_from_user(ioc, (void __user *)arg, tmp)) { 459 kfree(ioc); 460 retval = -EFAULT; 461 break; 462 } 463 464 /* translate to spi_message, execute */ 465 retval = spidev_message(spidev, ioc, n_ioc); 466 kfree(ioc); 467 break; 468 } 469 470 mutex_unlock(&spidev->buf_lock); 471 spi_dev_put(spi); 472 return retval; 473 } 474 475 #ifdef CONFIG_COMPAT 476 static long 477 spidev_compat_ioctl(struct file *filp, unsigned int cmd, unsigned long arg) 478 { 479 return spidev_ioctl(filp, cmd, (unsigned long)compat_ptr(arg)); 480 } 481 #else 482 #define spidev_compat_ioctl NULL 483 #endif /* CONFIG_COMPAT */ 484 485 static int spidev_open(struct inode *inode, struct file *filp) 486 { 487 struct spidev_data *spidev; 488 int status = -ENXIO; 489 490 mutex_lock(&device_list_lock); 491 492 list_for_each_entry(spidev, &device_list, device_entry) { 493 if (spidev->devt == inode->i_rdev) { 494 status = 0; 495 break; 496 } 497 } 498 if (status == 0) { 499 if (!spidev->buffer) { 500 spidev->buffer = kmalloc(bufsiz, GFP_KERNEL); 501 if (!spidev->buffer) { 502 dev_dbg(&spidev->spi->dev, "open/ENOMEM\n"); 503 status = -ENOMEM; 504 } 505 } 506 if (status == 0) { 507 spidev->users++; 508 filp->private_data = spidev; 509 nonseekable_open(inode, filp); 510 } 511 } else 512 pr_debug("spidev: nothing for minor %d\n", iminor(inode)); 513 514 mutex_unlock(&device_list_lock); 515 return status; 516 } 517 518 static int spidev_release(struct inode *inode, struct file *filp) 519 { 520 struct spidev_data *spidev; 521 int status = 0; 522 523 mutex_lock(&device_list_lock); 524 spidev = filp->private_data; 525 filp->private_data = NULL; 526 527 /* last close? */ 528 spidev->users--; 529 if (!spidev->users) { 530 int dofree; 531 532 kfree(spidev->buffer); 533 spidev->buffer = NULL; 534 535 /* ... after we unbound from the underlying device? */ 536 spin_lock_irq(&spidev->spi_lock); 537 dofree = (spidev->spi == NULL); 538 spin_unlock_irq(&spidev->spi_lock); 539 540 if (dofree) 541 kfree(spidev); 542 } 543 mutex_unlock(&device_list_lock); 544 545 return status; 546 } 547 548 static const struct file_operations spidev_fops = { 549 .owner = THIS_MODULE, 550 /* REVISIT switch to aio primitives, so that userspace 551 * gets more complete API coverage. It'll simplify things 552 * too, except for the locking. 553 */ 554 .write = spidev_write, 555 .read = spidev_read, 556 .unlocked_ioctl = spidev_ioctl, 557 .compat_ioctl = spidev_compat_ioctl, 558 .open = spidev_open, 559 .release = spidev_release, 560 .llseek = no_llseek, 561 }; 562 563 /*-------------------------------------------------------------------------*/ 564 565 /* The main reason to have this class is to make mdev/udev create the 566 * /dev/spidevB.C character device nodes exposing our userspace API. 567 * It also simplifies memory management. 568 */ 569 570 static struct class *spidev_class; 571 572 /*-------------------------------------------------------------------------*/ 573 574 static int __devinit spidev_probe(struct spi_device *spi) 575 { 576 struct spidev_data *spidev; 577 int status; 578 unsigned long minor; 579 580 /* Allocate driver data */ 581 spidev = kzalloc(sizeof(*spidev), GFP_KERNEL); 582 if (!spidev) 583 return -ENOMEM; 584 585 /* Initialize the driver data */ 586 spidev->spi = spi; 587 spin_lock_init(&spidev->spi_lock); 588 mutex_init(&spidev->buf_lock); 589 590 INIT_LIST_HEAD(&spidev->device_entry); 591 592 /* If we can allocate a minor number, hook up this device. 593 * Reusing minors is fine so long as udev or mdev is working. 594 */ 595 mutex_lock(&device_list_lock); 596 minor = find_first_zero_bit(minors, N_SPI_MINORS); 597 if (minor < N_SPI_MINORS) { 598 struct device *dev; 599 600 spidev->devt = MKDEV(SPIDEV_MAJOR, minor); 601 dev = device_create(spidev_class, &spi->dev, spidev->devt, 602 spidev, "spidev%d.%d", 603 spi->master->bus_num, spi->chip_select); 604 status = IS_ERR(dev) ? PTR_ERR(dev) : 0; 605 } else { 606 dev_dbg(&spi->dev, "no minor number available!\n"); 607 status = -ENODEV; 608 } 609 if (status == 0) { 610 set_bit(minor, minors); 611 list_add(&spidev->device_entry, &device_list); 612 } 613 mutex_unlock(&device_list_lock); 614 615 if (status == 0) 616 spi_set_drvdata(spi, spidev); 617 else 618 kfree(spidev); 619 620 return status; 621 } 622 623 static int __devexit spidev_remove(struct spi_device *spi) 624 { 625 struct spidev_data *spidev = spi_get_drvdata(spi); 626 627 /* make sure ops on existing fds can abort cleanly */ 628 spin_lock_irq(&spidev->spi_lock); 629 spidev->spi = NULL; 630 spi_set_drvdata(spi, NULL); 631 spin_unlock_irq(&spidev->spi_lock); 632 633 /* prevent new opens */ 634 mutex_lock(&device_list_lock); 635 list_del(&spidev->device_entry); 636 device_destroy(spidev_class, spidev->devt); 637 clear_bit(MINOR(spidev->devt), minors); 638 if (spidev->users == 0) 639 kfree(spidev); 640 mutex_unlock(&device_list_lock); 641 642 return 0; 643 } 644 645 static struct spi_driver spidev_spi_driver = { 646 .driver = { 647 .name = "spidev", 648 .owner = THIS_MODULE, 649 }, 650 .probe = spidev_probe, 651 .remove = __devexit_p(spidev_remove), 652 653 /* NOTE: suspend/resume methods are not necessary here. 654 * We don't do anything except pass the requests to/from 655 * the underlying controller. The refrigerator handles 656 * most issues; the controller driver handles the rest. 657 */ 658 }; 659 660 /*-------------------------------------------------------------------------*/ 661 662 static int __init spidev_init(void) 663 { 664 int status; 665 666 /* Claim our 256 reserved device numbers. Then register a class 667 * that will key udev/mdev to add/remove /dev nodes. Last, register 668 * the driver which manages those device numbers. 669 */ 670 BUILD_BUG_ON(N_SPI_MINORS > 256); 671 status = register_chrdev(SPIDEV_MAJOR, "spi", &spidev_fops); 672 if (status < 0) 673 return status; 674 675 spidev_class = class_create(THIS_MODULE, "spidev"); 676 if (IS_ERR(spidev_class)) { 677 unregister_chrdev(SPIDEV_MAJOR, spidev_spi_driver.driver.name); 678 return PTR_ERR(spidev_class); 679 } 680 681 status = spi_register_driver(&spidev_spi_driver); 682 if (status < 0) { 683 class_destroy(spidev_class); 684 unregister_chrdev(SPIDEV_MAJOR, spidev_spi_driver.driver.name); 685 } 686 return status; 687 } 688 module_init(spidev_init); 689 690 static void __exit spidev_exit(void) 691 { 692 spi_unregister_driver(&spidev_spi_driver); 693 class_destroy(spidev_class); 694 unregister_chrdev(SPIDEV_MAJOR, spidev_spi_driver.driver.name); 695 } 696 module_exit(spidev_exit); 697 698 MODULE_AUTHOR("Andrea Paterniani, <a.paterniani@swapp-eng.it>"); 699 MODULE_DESCRIPTION("User mode SPI device interface"); 700 MODULE_LICENSE("GPL"); 701 MODULE_ALIAS("spi:spidev"); 702