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