1 /* 2 * 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 #include <linux/of.h> 35 #include <linux/of_device.h> 36 37 #include <linux/spi/spi.h> 38 #include <linux/spi/spidev.h> 39 40 #include <asm/uaccess.h> 41 42 43 /* 44 * This supports access to SPI devices using normal userspace I/O calls. 45 * Note that while traditional UNIX/POSIX I/O semantics are half duplex, 46 * and often mask message boundaries, full SPI support requires full duplex 47 * transfers. There are several kinds of internal message boundaries to 48 * handle chipselect management and other protocol options. 49 * 50 * SPI has a character major number assigned. We allocate minor numbers 51 * dynamically using a bitmask. You must use hotplug tools, such as udev 52 * (or mdev with busybox) to create and destroy the /dev/spidevB.C device 53 * nodes, since there is no fixed association of minor numbers with any 54 * particular SPI bus or device. 55 */ 56 #define SPIDEV_MAJOR 153 /* assigned */ 57 #define N_SPI_MINORS 32 /* ... up to 256 */ 58 59 static DECLARE_BITMAP(minors, N_SPI_MINORS); 60 61 62 /* Bit masks for spi_device.mode management. Note that incorrect 63 * settings for some settings can cause *lots* of trouble for other 64 * devices on a shared bus: 65 * 66 * - CS_HIGH ... this device will be active when it shouldn't be 67 * - 3WIRE ... when active, it won't behave as it should 68 * - NO_CS ... there will be no explicit message boundaries; this 69 * is completely incompatible with the shared bus model 70 * - READY ... transfers may proceed when they shouldn't. 71 * 72 * REVISIT should changing those flags be privileged? 73 */ 74 #define SPI_MODE_MASK (SPI_CPHA | SPI_CPOL | SPI_CS_HIGH \ 75 | SPI_LSB_FIRST | SPI_3WIRE | SPI_LOOP \ 76 | SPI_NO_CS | SPI_READY) 77 78 struct spidev_data { 79 dev_t devt; 80 spinlock_t spi_lock; 81 struct spi_device *spi; 82 struct list_head device_entry; 83 84 /* buffer is NULL unless this device is open (users > 0) */ 85 struct mutex buf_lock; 86 unsigned users; 87 u8 *buffer; 88 }; 89 90 static LIST_HEAD(device_list); 91 static DEFINE_MUTEX(device_list_lock); 92 93 static unsigned bufsiz = 4096; 94 module_param(bufsiz, uint, S_IRUGO); 95 MODULE_PARM_DESC(bufsiz, "data bytes in biggest supported SPI message"); 96 97 /*-------------------------------------------------------------------------*/ 98 99 /* 100 * We can't use the standard synchronous wrappers for file I/O; we 101 * need to protect against async removal of the underlying spi_device. 102 */ 103 static void spidev_complete(void *arg) 104 { 105 complete(arg); 106 } 107 108 static ssize_t 109 spidev_sync(struct spidev_data *spidev, struct spi_message *message) 110 { 111 DECLARE_COMPLETION_ONSTACK(done); 112 int status; 113 114 message->complete = spidev_complete; 115 message->context = &done; 116 117 spin_lock_irq(&spidev->spi_lock); 118 if (spidev->spi == NULL) 119 status = -ESHUTDOWN; 120 else 121 status = spi_async(spidev->spi, message); 122 spin_unlock_irq(&spidev->spi_lock); 123 124 if (status == 0) { 125 wait_for_completion(&done); 126 status = message->status; 127 if (status == 0) 128 status = message->actual_length; 129 } 130 return status; 131 } 132 133 static inline ssize_t 134 spidev_sync_write(struct spidev_data *spidev, size_t len) 135 { 136 struct spi_transfer t = { 137 .tx_buf = spidev->buffer, 138 .len = len, 139 }; 140 struct spi_message m; 141 142 spi_message_init(&m); 143 spi_message_add_tail(&t, &m); 144 return spidev_sync(spidev, &m); 145 } 146 147 static inline ssize_t 148 spidev_sync_read(struct spidev_data *spidev, size_t len) 149 { 150 struct spi_transfer t = { 151 .rx_buf = spidev->buffer, 152 .len = len, 153 }; 154 struct spi_message m; 155 156 spi_message_init(&m); 157 spi_message_add_tail(&t, &m); 158 return spidev_sync(spidev, &m); 159 } 160 161 /*-------------------------------------------------------------------------*/ 162 163 /* Read-only message with current device setup */ 164 static ssize_t 165 spidev_read(struct file *filp, char __user *buf, size_t count, loff_t *f_pos) 166 { 167 struct spidev_data *spidev; 168 ssize_t status = 0; 169 170 /* chipselect only toggles at start or end of operation */ 171 if (count > bufsiz) 172 return -EMSGSIZE; 173 174 spidev = filp->private_data; 175 176 mutex_lock(&spidev->buf_lock); 177 status = spidev_sync_read(spidev, count); 178 if (status > 0) { 179 unsigned long missing; 180 181 missing = copy_to_user(buf, spidev->buffer, status); 182 if (missing == status) 183 status = -EFAULT; 184 else 185 status = status - missing; 186 } 187 mutex_unlock(&spidev->buf_lock); 188 189 return status; 190 } 191 192 /* Write-only message with current device setup */ 193 static ssize_t 194 spidev_write(struct file *filp, const char __user *buf, 195 size_t count, loff_t *f_pos) 196 { 197 struct spidev_data *spidev; 198 ssize_t status = 0; 199 unsigned long missing; 200 201 /* chipselect only toggles at start or end of operation */ 202 if (count > bufsiz) 203 return -EMSGSIZE; 204 205 spidev = filp->private_data; 206 207 mutex_lock(&spidev->buf_lock); 208 missing = copy_from_user(spidev->buffer, buf, count); 209 if (missing == 0) { 210 status = spidev_sync_write(spidev, count); 211 } else 212 status = -EFAULT; 213 mutex_unlock(&spidev->buf_lock); 214 215 return status; 216 } 217 218 static int spidev_message(struct spidev_data *spidev, 219 struct spi_ioc_transfer *u_xfers, unsigned n_xfers) 220 { 221 struct spi_message msg; 222 struct spi_transfer *k_xfers; 223 struct spi_transfer *k_tmp; 224 struct spi_ioc_transfer *u_tmp; 225 unsigned n, total; 226 u8 *buf; 227 int status = -EFAULT; 228 229 spi_message_init(&msg); 230 k_xfers = kcalloc(n_xfers, sizeof(*k_tmp), GFP_KERNEL); 231 if (k_xfers == NULL) 232 return -ENOMEM; 233 234 /* Construct spi_message, copying any tx data to bounce buffer. 235 * We walk the array of user-provided transfers, using each one 236 * to initialize a kernel version of the same transfer. 237 */ 238 buf = spidev->buffer; 239 total = 0; 240 for (n = n_xfers, k_tmp = k_xfers, u_tmp = u_xfers; 241 n; 242 n--, k_tmp++, u_tmp++) { 243 k_tmp->len = u_tmp->len; 244 245 total += k_tmp->len; 246 if (total > bufsiz) { 247 status = -EMSGSIZE; 248 goto done; 249 } 250 251 if (u_tmp->rx_buf) { 252 k_tmp->rx_buf = buf; 253 if (!access_ok(VERIFY_WRITE, (u8 __user *) 254 (uintptr_t) u_tmp->rx_buf, 255 u_tmp->len)) 256 goto done; 257 } 258 if (u_tmp->tx_buf) { 259 k_tmp->tx_buf = buf; 260 if (copy_from_user(buf, (const u8 __user *) 261 (uintptr_t) u_tmp->tx_buf, 262 u_tmp->len)) 263 goto done; 264 } 265 buf += k_tmp->len; 266 267 k_tmp->cs_change = !!u_tmp->cs_change; 268 k_tmp->bits_per_word = u_tmp->bits_per_word; 269 k_tmp->delay_usecs = u_tmp->delay_usecs; 270 k_tmp->speed_hz = u_tmp->speed_hz; 271 #ifdef VERBOSE 272 dev_dbg(&spidev->spi->dev, 273 " xfer len %zd %s%s%s%dbits %u usec %uHz\n", 274 u_tmp->len, 275 u_tmp->rx_buf ? "rx " : "", 276 u_tmp->tx_buf ? "tx " : "", 277 u_tmp->cs_change ? "cs " : "", 278 u_tmp->bits_per_word ? : spidev->spi->bits_per_word, 279 u_tmp->delay_usecs, 280 u_tmp->speed_hz ? : spidev->spi->max_speed_hz); 281 #endif 282 spi_message_add_tail(k_tmp, &msg); 283 } 284 285 status = spidev_sync(spidev, &msg); 286 if (status < 0) 287 goto done; 288 289 /* copy any rx data out of bounce buffer */ 290 buf = spidev->buffer; 291 for (n = n_xfers, u_tmp = u_xfers; n; n--, u_tmp++) { 292 if (u_tmp->rx_buf) { 293 if (__copy_to_user((u8 __user *) 294 (uintptr_t) u_tmp->rx_buf, buf, 295 u_tmp->len)) { 296 status = -EFAULT; 297 goto done; 298 } 299 } 300 buf += u_tmp->len; 301 } 302 status = total; 303 304 done: 305 kfree(k_xfers); 306 return status; 307 } 308 309 static long 310 spidev_ioctl(struct file *filp, unsigned int cmd, unsigned long arg) 311 { 312 int err = 0; 313 int retval = 0; 314 struct spidev_data *spidev; 315 struct spi_device *spi; 316 u32 tmp; 317 unsigned n_ioc; 318 struct spi_ioc_transfer *ioc; 319 320 /* Check type and command number */ 321 if (_IOC_TYPE(cmd) != SPI_IOC_MAGIC) 322 return -ENOTTY; 323 324 /* Check access direction once here; don't repeat below. 325 * IOC_DIR is from the user perspective, while access_ok is 326 * from the kernel perspective; so they look reversed. 327 */ 328 if (_IOC_DIR(cmd) & _IOC_READ) 329 err = !access_ok(VERIFY_WRITE, 330 (void __user *)arg, _IOC_SIZE(cmd)); 331 if (err == 0 && _IOC_DIR(cmd) & _IOC_WRITE) 332 err = !access_ok(VERIFY_READ, 333 (void __user *)arg, _IOC_SIZE(cmd)); 334 if (err) 335 return -EFAULT; 336 337 /* guard against device removal before, or while, 338 * we issue this ioctl. 339 */ 340 spidev = filp->private_data; 341 spin_lock_irq(&spidev->spi_lock); 342 spi = spi_dev_get(spidev->spi); 343 spin_unlock_irq(&spidev->spi_lock); 344 345 if (spi == NULL) 346 return -ESHUTDOWN; 347 348 /* use the buffer lock here for triple duty: 349 * - prevent I/O (from us) so calling spi_setup() is safe; 350 * - prevent concurrent SPI_IOC_WR_* from morphing 351 * data fields while SPI_IOC_RD_* reads them; 352 * - SPI_IOC_MESSAGE needs the buffer locked "normally". 353 */ 354 mutex_lock(&spidev->buf_lock); 355 356 switch (cmd) { 357 /* read requests */ 358 case SPI_IOC_RD_MODE: 359 retval = __put_user(spi->mode & SPI_MODE_MASK, 360 (__u8 __user *)arg); 361 break; 362 case SPI_IOC_RD_LSB_FIRST: 363 retval = __put_user((spi->mode & SPI_LSB_FIRST) ? 1 : 0, 364 (__u8 __user *)arg); 365 break; 366 case SPI_IOC_RD_BITS_PER_WORD: 367 retval = __put_user(spi->bits_per_word, (__u8 __user *)arg); 368 break; 369 case SPI_IOC_RD_MAX_SPEED_HZ: 370 retval = __put_user(spi->max_speed_hz, (__u32 __user *)arg); 371 break; 372 373 /* write requests */ 374 case SPI_IOC_WR_MODE: 375 retval = __get_user(tmp, (u8 __user *)arg); 376 if (retval == 0) { 377 u8 save = spi->mode; 378 379 if (tmp & ~SPI_MODE_MASK) { 380 retval = -EINVAL; 381 break; 382 } 383 384 tmp |= spi->mode & ~SPI_MODE_MASK; 385 spi->mode = (u8)tmp; 386 retval = spi_setup(spi); 387 if (retval < 0) 388 spi->mode = save; 389 else 390 dev_dbg(&spi->dev, "spi mode %02x\n", tmp); 391 } 392 break; 393 case SPI_IOC_WR_LSB_FIRST: 394 retval = __get_user(tmp, (__u8 __user *)arg); 395 if (retval == 0) { 396 u8 save = spi->mode; 397 398 if (tmp) 399 spi->mode |= SPI_LSB_FIRST; 400 else 401 spi->mode &= ~SPI_LSB_FIRST; 402 retval = spi_setup(spi); 403 if (retval < 0) 404 spi->mode = save; 405 else 406 dev_dbg(&spi->dev, "%csb first\n", 407 tmp ? 'l' : 'm'); 408 } 409 break; 410 case SPI_IOC_WR_BITS_PER_WORD: 411 retval = __get_user(tmp, (__u8 __user *)arg); 412 if (retval == 0) { 413 u8 save = spi->bits_per_word; 414 415 spi->bits_per_word = tmp; 416 retval = spi_setup(spi); 417 if (retval < 0) 418 spi->bits_per_word = save; 419 else 420 dev_dbg(&spi->dev, "%d bits per word\n", tmp); 421 } 422 break; 423 case SPI_IOC_WR_MAX_SPEED_HZ: 424 retval = __get_user(tmp, (__u32 __user *)arg); 425 if (retval == 0) { 426 u32 save = spi->max_speed_hz; 427 428 spi->max_speed_hz = tmp; 429 retval = spi_setup(spi); 430 if (retval < 0) 431 spi->max_speed_hz = save; 432 else 433 dev_dbg(&spi->dev, "%d Hz (max)\n", tmp); 434 } 435 break; 436 437 default: 438 /* segmented and/or full-duplex I/O request */ 439 if (_IOC_NR(cmd) != _IOC_NR(SPI_IOC_MESSAGE(0)) 440 || _IOC_DIR(cmd) != _IOC_WRITE) { 441 retval = -ENOTTY; 442 break; 443 } 444 445 tmp = _IOC_SIZE(cmd); 446 if ((tmp % sizeof(struct spi_ioc_transfer)) != 0) { 447 retval = -EINVAL; 448 break; 449 } 450 n_ioc = tmp / sizeof(struct spi_ioc_transfer); 451 if (n_ioc == 0) 452 break; 453 454 /* copy into scratch area */ 455 ioc = kmalloc(tmp, GFP_KERNEL); 456 if (!ioc) { 457 retval = -ENOMEM; 458 break; 459 } 460 if (__copy_from_user(ioc, (void __user *)arg, tmp)) { 461 kfree(ioc); 462 retval = -EFAULT; 463 break; 464 } 465 466 /* translate to spi_message, execute */ 467 retval = spidev_message(spidev, ioc, n_ioc); 468 kfree(ioc); 469 break; 470 } 471 472 mutex_unlock(&spidev->buf_lock); 473 spi_dev_put(spi); 474 return retval; 475 } 476 477 #ifdef CONFIG_COMPAT 478 static long 479 spidev_compat_ioctl(struct file *filp, unsigned int cmd, unsigned long arg) 480 { 481 return spidev_ioctl(filp, cmd, (unsigned long)compat_ptr(arg)); 482 } 483 #else 484 #define spidev_compat_ioctl NULL 485 #endif /* CONFIG_COMPAT */ 486 487 static int spidev_open(struct inode *inode, struct file *filp) 488 { 489 struct spidev_data *spidev; 490 int status = -ENXIO; 491 492 mutex_lock(&device_list_lock); 493 494 list_for_each_entry(spidev, &device_list, device_entry) { 495 if (spidev->devt == inode->i_rdev) { 496 status = 0; 497 break; 498 } 499 } 500 if (status == 0) { 501 if (!spidev->buffer) { 502 spidev->buffer = kmalloc(bufsiz, GFP_KERNEL); 503 if (!spidev->buffer) { 504 dev_dbg(&spidev->spi->dev, "open/ENOMEM\n"); 505 status = -ENOMEM; 506 } 507 } 508 if (status == 0) { 509 spidev->users++; 510 filp->private_data = spidev; 511 nonseekable_open(inode, filp); 512 } 513 } else 514 pr_debug("spidev: nothing for minor %d\n", iminor(inode)); 515 516 mutex_unlock(&device_list_lock); 517 return status; 518 } 519 520 static int spidev_release(struct inode *inode, struct file *filp) 521 { 522 struct spidev_data *spidev; 523 int status = 0; 524 525 mutex_lock(&device_list_lock); 526 spidev = filp->private_data; 527 filp->private_data = NULL; 528 529 /* last close? */ 530 spidev->users--; 531 if (!spidev->users) { 532 int dofree; 533 534 kfree(spidev->buffer); 535 spidev->buffer = NULL; 536 537 /* ... after we unbound from the underlying device? */ 538 spin_lock_irq(&spidev->spi_lock); 539 dofree = (spidev->spi == NULL); 540 spin_unlock_irq(&spidev->spi_lock); 541 542 if (dofree) 543 kfree(spidev); 544 } 545 mutex_unlock(&device_list_lock); 546 547 return status; 548 } 549 550 static const struct file_operations spidev_fops = { 551 .owner = THIS_MODULE, 552 /* REVISIT switch to aio primitives, so that userspace 553 * gets more complete API coverage. It'll simplify things 554 * too, except for the locking. 555 */ 556 .write = spidev_write, 557 .read = spidev_read, 558 .unlocked_ioctl = spidev_ioctl, 559 .compat_ioctl = spidev_compat_ioctl, 560 .open = spidev_open, 561 .release = spidev_release, 562 .llseek = no_llseek, 563 }; 564 565 /*-------------------------------------------------------------------------*/ 566 567 /* The main reason to have this class is to make mdev/udev create the 568 * /dev/spidevB.C character device nodes exposing our userspace API. 569 * It also simplifies memory management. 570 */ 571 572 static struct class *spidev_class; 573 574 /*-------------------------------------------------------------------------*/ 575 576 static int spidev_probe(struct spi_device *spi) 577 { 578 struct spidev_data *spidev; 579 int status; 580 unsigned long minor; 581 582 /* Allocate driver data */ 583 spidev = kzalloc(sizeof(*spidev), GFP_KERNEL); 584 if (!spidev) 585 return -ENOMEM; 586 587 /* Initialize the driver data */ 588 spidev->spi = spi; 589 spin_lock_init(&spidev->spi_lock); 590 mutex_init(&spidev->buf_lock); 591 592 INIT_LIST_HEAD(&spidev->device_entry); 593 594 /* If we can allocate a minor number, hook up this device. 595 * Reusing minors is fine so long as udev or mdev is working. 596 */ 597 mutex_lock(&device_list_lock); 598 minor = find_first_zero_bit(minors, N_SPI_MINORS); 599 if (minor < N_SPI_MINORS) { 600 struct device *dev; 601 602 spidev->devt = MKDEV(SPIDEV_MAJOR, minor); 603 dev = device_create(spidev_class, &spi->dev, spidev->devt, 604 spidev, "spidev%d.%d", 605 spi->master->bus_num, spi->chip_select); 606 status = PTR_ERR_OR_ZERO(dev); 607 } else { 608 dev_dbg(&spi->dev, "no minor number available!\n"); 609 status = -ENODEV; 610 } 611 if (status == 0) { 612 set_bit(minor, minors); 613 list_add(&spidev->device_entry, &device_list); 614 } 615 mutex_unlock(&device_list_lock); 616 617 if (status == 0) 618 spi_set_drvdata(spi, spidev); 619 else 620 kfree(spidev); 621 622 return status; 623 } 624 625 static int spidev_remove(struct spi_device *spi) 626 { 627 struct spidev_data *spidev = spi_get_drvdata(spi); 628 629 /* make sure ops on existing fds can abort cleanly */ 630 spin_lock_irq(&spidev->spi_lock); 631 spidev->spi = NULL; 632 spi_set_drvdata(spi, NULL); 633 spin_unlock_irq(&spidev->spi_lock); 634 635 /* prevent new opens */ 636 mutex_lock(&device_list_lock); 637 list_del(&spidev->device_entry); 638 device_destroy(spidev_class, spidev->devt); 639 clear_bit(MINOR(spidev->devt), minors); 640 if (spidev->users == 0) 641 kfree(spidev); 642 mutex_unlock(&device_list_lock); 643 644 return 0; 645 } 646 647 static const struct of_device_id spidev_dt_ids[] = { 648 { .compatible = "rohm,dh2228fv" }, 649 {}, 650 }; 651 652 MODULE_DEVICE_TABLE(of, spidev_dt_ids); 653 654 static struct spi_driver spidev_spi_driver = { 655 .driver = { 656 .name = "spidev", 657 .owner = THIS_MODULE, 658 .of_match_table = of_match_ptr(spidev_dt_ids), 659 }, 660 .probe = spidev_probe, 661 .remove = spidev_remove, 662 663 /* NOTE: suspend/resume methods are not necessary here. 664 * We don't do anything except pass the requests to/from 665 * the underlying controller. The refrigerator handles 666 * most issues; the controller driver handles the rest. 667 */ 668 }; 669 670 /*-------------------------------------------------------------------------*/ 671 672 static int __init spidev_init(void) 673 { 674 int status; 675 676 /* Claim our 256 reserved device numbers. Then register a class 677 * that will key udev/mdev to add/remove /dev nodes. Last, register 678 * the driver which manages those device numbers. 679 */ 680 BUILD_BUG_ON(N_SPI_MINORS > 256); 681 status = register_chrdev(SPIDEV_MAJOR, "spi", &spidev_fops); 682 if (status < 0) 683 return status; 684 685 spidev_class = class_create(THIS_MODULE, "spidev"); 686 if (IS_ERR(spidev_class)) { 687 unregister_chrdev(SPIDEV_MAJOR, spidev_spi_driver.driver.name); 688 return PTR_ERR(spidev_class); 689 } 690 691 status = spi_register_driver(&spidev_spi_driver); 692 if (status < 0) { 693 class_destroy(spidev_class); 694 unregister_chrdev(SPIDEV_MAJOR, spidev_spi_driver.driver.name); 695 } 696 return status; 697 } 698 module_init(spidev_init); 699 700 static void __exit spidev_exit(void) 701 { 702 spi_unregister_driver(&spidev_spi_driver); 703 class_destroy(spidev_class); 704 unregister_chrdev(SPIDEV_MAJOR, spidev_spi_driver.driver.name); 705 } 706 module_exit(spidev_exit); 707 708 MODULE_AUTHOR("Andrea Paterniani, <a.paterniani@swapp-eng.it>"); 709 MODULE_DESCRIPTION("User mode SPI device interface"); 710 MODULE_LICENSE("GPL"); 711 MODULE_ALIAS("spi:spidev"); 712