Root/drivers/usb/usb-skeleton.c

1/*
2 * USB Skeleton driver - 2.2
3 *
4 * Copyright (C) 2001-2004 Greg Kroah-Hartman (greg@kroah.com)
5 *
6 * This program is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU General Public License as
8 * published by the Free Software Foundation, version 2.
9 *
10 * This driver is based on the 2.6.3 version of drivers/usb/usb-skeleton.c
11 * but has been rewritten to be easier to read and use.
12 *
13 */
14
15#include <linux/kernel.h>
16#include <linux/errno.h>
17#include <linux/init.h>
18#include <linux/slab.h>
19#include <linux/module.h>
20#include <linux/kref.h>
21#include <linux/uaccess.h>
22#include <linux/usb.h>
23#include <linux/mutex.h>
24
25
26/* Define these values to match your devices */
27#define USB_SKEL_VENDOR_ID 0xfff0
28#define USB_SKEL_PRODUCT_ID 0xfff0
29
30/* table of devices that work with this driver */
31static const struct usb_device_id skel_table[] = {
32    { USB_DEVICE(USB_SKEL_VENDOR_ID, USB_SKEL_PRODUCT_ID) },
33    { } /* Terminating entry */
34};
35MODULE_DEVICE_TABLE(usb, skel_table);
36
37
38/* Get a minor range for your devices from the usb maintainer */
39#define USB_SKEL_MINOR_BASE 192
40
41/* our private defines. if this grows any larger, use your own .h file */
42#define MAX_TRANSFER (PAGE_SIZE - 512)
43/* MAX_TRANSFER is chosen so that the VM is not stressed by
44   allocations > PAGE_SIZE and the number of packets in a page
45   is an integer 512 is the largest possible packet on EHCI */
46#define WRITES_IN_FLIGHT 8
47/* arbitrarily chosen */
48
49/* Structure to hold all of our device specific stuff */
50struct usb_skel {
51    struct usb_device *udev; /* the usb device for this device */
52    struct usb_interface *interface; /* the interface for this device */
53    struct semaphore limit_sem; /* limiting the number of writes in progress */
54    struct usb_anchor submitted; /* in case we need to retract our submissions */
55    struct urb *bulk_in_urb; /* the urb to read data with */
56    unsigned char *bulk_in_buffer; /* the buffer to receive data */
57    size_t bulk_in_size; /* the size of the receive buffer */
58    size_t bulk_in_filled; /* number of bytes in the buffer */
59    size_t bulk_in_copied; /* already copied to user space */
60    __u8 bulk_in_endpointAddr; /* the address of the bulk in endpoint */
61    __u8 bulk_out_endpointAddr; /* the address of the bulk out endpoint */
62    int errors; /* the last request tanked */
63    bool ongoing_read; /* a read is going on */
64    bool processed_urb; /* indicates we haven't processed the urb */
65    spinlock_t err_lock; /* lock for errors */
66    struct kref kref;
67    struct mutex io_mutex; /* synchronize I/O with disconnect */
68    struct completion bulk_in_completion; /* to wait for an ongoing read */
69};
70#define to_skel_dev(d) container_of(d, struct usb_skel, kref)
71
72static struct usb_driver skel_driver;
73static void skel_draw_down(struct usb_skel *dev);
74
75static void skel_delete(struct kref *kref)
76{
77    struct usb_skel *dev = to_skel_dev(kref);
78
79    usb_free_urb(dev->bulk_in_urb);
80    usb_put_dev(dev->udev);
81    kfree(dev->bulk_in_buffer);
82    kfree(dev);
83}
84
85static int skel_open(struct inode *inode, struct file *file)
86{
87    struct usb_skel *dev;
88    struct usb_interface *interface;
89    int subminor;
90    int retval = 0;
91
92    subminor = iminor(inode);
93
94    interface = usb_find_interface(&skel_driver, subminor);
95    if (!interface) {
96        pr_err("%s - error, can't find device for minor %d\n",
97            __func__, subminor);
98        retval = -ENODEV;
99        goto exit;
100    }
101
102    dev = usb_get_intfdata(interface);
103    if (!dev) {
104        retval = -ENODEV;
105        goto exit;
106    }
107
108    /* increment our usage count for the device */
109    kref_get(&dev->kref);
110
111    /* lock the device to allow correctly handling errors
112     * in resumption */
113    mutex_lock(&dev->io_mutex);
114
115    retval = usb_autopm_get_interface(interface);
116    if (retval)
117        goto out_err;
118
119    /* save our object in the file's private structure */
120    file->private_data = dev;
121    mutex_unlock(&dev->io_mutex);
122
123exit:
124    return retval;
125}
126
127static int skel_release(struct inode *inode, struct file *file)
128{
129    struct usb_skel *dev;
130
131    dev = file->private_data;
132    if (dev == NULL)
133        return -ENODEV;
134
135    /* allow the device to be autosuspended */
136    mutex_lock(&dev->io_mutex);
137    if (dev->interface)
138        usb_autopm_put_interface(dev->interface);
139    mutex_unlock(&dev->io_mutex);
140
141    /* decrement the count on our device */
142    kref_put(&dev->kref, skel_delete);
143    return 0;
144}
145
146static int skel_flush(struct file *file, fl_owner_t id)
147{
148    struct usb_skel *dev;
149    int res;
150
151    dev = file->private_data;
152    if (dev == NULL)
153        return -ENODEV;
154
155    /* wait for io to stop */
156    mutex_lock(&dev->io_mutex);
157    skel_draw_down(dev);
158
159    /* read out errors, leave subsequent opens a clean slate */
160    spin_lock_irq(&dev->err_lock);
161    res = dev->errors ? (dev->errors == -EPIPE ? -EPIPE : -EIO) : 0;
162    dev->errors = 0;
163    spin_unlock_irq(&dev->err_lock);
164
165    mutex_unlock(&dev->io_mutex);
166
167    return res;
168}
169
170static void skel_read_bulk_callback(struct urb *urb)
171{
172    struct usb_skel *dev;
173
174    dev = urb->context;
175
176    spin_lock(&dev->err_lock);
177    /* sync/async unlink faults aren't errors */
178    if (urb->status) {
179        if (!(urb->status == -ENOENT ||
180            urb->status == -ECONNRESET ||
181            urb->status == -ESHUTDOWN))
182            dev_err(&dev->interface->dev,
183                "%s - nonzero write bulk status received: %d\n",
184                __func__, urb->status);
185
186        dev->errors = urb->status;
187    } else {
188        dev->bulk_in_filled = urb->actual_length;
189    }
190    dev->ongoing_read = 0;
191    spin_unlock(&dev->err_lock);
192
193    complete(&dev->bulk_in_completion);
194}
195
196static int skel_do_read_io(struct usb_skel *dev, size_t count)
197{
198    int rv;
199
200    /* prepare a read */
201    usb_fill_bulk_urb(dev->bulk_in_urb,
202            dev->udev,
203            usb_rcvbulkpipe(dev->udev,
204                dev->bulk_in_endpointAddr),
205            dev->bulk_in_buffer,
206            min(dev->bulk_in_size, count),
207            skel_read_bulk_callback,
208            dev);
209    /* tell everybody to leave the URB alone */
210    spin_lock_irq(&dev->err_lock);
211    dev->ongoing_read = 1;
212    spin_unlock_irq(&dev->err_lock);
213
214    /* do it */
215    rv = usb_submit_urb(dev->bulk_in_urb, GFP_KERNEL);
216    if (rv < 0) {
217        dev_err(&dev->interface->dev,
218            "%s - failed submitting read urb, error %d\n",
219            __func__, rv);
220        dev->bulk_in_filled = 0;
221        rv = (rv == -ENOMEM) ? rv : -EIO;
222        spin_lock_irq(&dev->err_lock);
223        dev->ongoing_read = 0;
224        spin_unlock_irq(&dev->err_lock);
225    }
226
227    return rv;
228}
229
230static ssize_t skel_read(struct file *file, char *buffer, size_t count,
231             loff_t *ppos)
232{
233    struct usb_skel *dev;
234    int rv;
235    bool ongoing_io;
236
237    dev = file->private_data;
238
239    /* if we cannot read at all, return EOF */
240    if (!dev->bulk_in_urb || !count)
241        return 0;
242
243    /* no concurrent readers */
244    rv = mutex_lock_interruptible(&dev->io_mutex);
245    if (rv < 0)
246        return rv;
247
248    if (!dev->interface) { /* disconnect() was called */
249        rv = -ENODEV;
250        goto exit;
251    }
252
253    /* if IO is under way, we must not touch things */
254retry:
255    spin_lock_irq(&dev->err_lock);
256    ongoing_io = dev->ongoing_read;
257    spin_unlock_irq(&dev->err_lock);
258
259    if (ongoing_io) {
260        /* nonblocking IO shall not wait */
261        if (file->f_flags & O_NONBLOCK) {
262            rv = -EAGAIN;
263            goto exit;
264        }
265        /*
266         * IO may take forever
267         * hence wait in an interruptible state
268         */
269        rv = wait_for_completion_interruptible(&dev->bulk_in_completion);
270        if (rv < 0)
271            goto exit;
272        /*
273         * by waiting we also semiprocessed the urb
274         * we must finish now
275         */
276        dev->bulk_in_copied = 0;
277        dev->processed_urb = 1;
278    }
279
280    if (!dev->processed_urb) {
281        /*
282         * the URB hasn't been processed
283         * do it now
284         */
285        wait_for_completion(&dev->bulk_in_completion);
286        dev->bulk_in_copied = 0;
287        dev->processed_urb = 1;
288    }
289
290    /* errors must be reported */
291    rv = dev->errors;
292    if (rv < 0) {
293        /* any error is reported once */
294        dev->errors = 0;
295        /* to preserve notifications about reset */
296        rv = (rv == -EPIPE) ? rv : -EIO;
297        /* no data to deliver */
298        dev->bulk_in_filled = 0;
299        /* report it */
300        goto exit;
301    }
302
303    /*
304     * if the buffer is filled we may satisfy the read
305     * else we need to start IO
306     */
307
308    if (dev->bulk_in_filled) {
309        /* we had read data */
310        size_t available = dev->bulk_in_filled - dev->bulk_in_copied;
311        size_t chunk = min(available, count);
312
313        if (!available) {
314            /*
315             * all data has been used
316             * actual IO needs to be done
317             */
318            rv = skel_do_read_io(dev, count);
319            if (rv < 0)
320                goto exit;
321            else
322                goto retry;
323        }
324        /*
325         * data is available
326         * chunk tells us how much shall be copied
327         */
328
329        if (copy_to_user(buffer,
330                 dev->bulk_in_buffer + dev->bulk_in_copied,
331                 chunk))
332            rv = -EFAULT;
333        else
334            rv = chunk;
335
336        dev->bulk_in_copied += chunk;
337
338        /*
339         * if we are asked for more than we have,
340         * we start IO but don't wait
341         */
342        if (available < count)
343            skel_do_read_io(dev, count - chunk);
344    } else {
345        /* no data in the buffer */
346        rv = skel_do_read_io(dev, count);
347        if (rv < 0)
348            goto exit;
349        else if (!(file->f_flags & O_NONBLOCK))
350            goto retry;
351        rv = -EAGAIN;
352    }
353exit:
354    mutex_unlock(&dev->io_mutex);
355    return rv;
356}
357
358static void skel_write_bulk_callback(struct urb *urb)
359{
360    struct usb_skel *dev;
361
362    dev = urb->context;
363
364    /* sync/async unlink faults aren't errors */
365    if (urb->status) {
366        if (!(urb->status == -ENOENT ||
367            urb->status == -ECONNRESET ||
368            urb->status == -ESHUTDOWN))
369            dev_err(&dev->interface->dev,
370                "%s - nonzero write bulk status received: %d\n",
371                __func__, urb->status);
372
373        spin_lock(&dev->err_lock);
374        dev->errors = urb->status;
375        spin_unlock(&dev->err_lock);
376    }
377
378    /* free up our allocated buffer */
379    usb_free_coherent(urb->dev, urb->transfer_buffer_length,
380              urb->transfer_buffer, urb->transfer_dma);
381    up(&dev->limit_sem);
382}
383
384static ssize_t skel_write(struct file *file, const char *user_buffer,
385              size_t count, loff_t *ppos)
386{
387    struct usb_skel *dev;
388    int retval = 0;
389    struct urb *urb = NULL;
390    char *buf = NULL;
391    size_t writesize = min(count, (size_t)MAX_TRANSFER);
392
393    dev = file->private_data;
394
395    /* verify that we actually have some data to write */
396    if (count == 0)
397        goto exit;
398
399    /*
400     * limit the number of URBs in flight to stop a user from using up all
401     * RAM
402     */
403    if (!(file->f_flags & O_NONBLOCK)) {
404        if (down_interruptible(&dev->limit_sem)) {
405            retval = -ERESTARTSYS;
406            goto exit;
407        }
408    } else {
409        if (down_trylock(&dev->limit_sem)) {
410            retval = -EAGAIN;
411            goto exit;
412        }
413    }
414
415    spin_lock_irq(&dev->err_lock);
416    retval = dev->errors;
417    if (retval < 0) {
418        /* any error is reported once */
419        dev->errors = 0;
420        /* to preserve notifications about reset */
421        retval = (retval == -EPIPE) ? retval : -EIO;
422    }
423    spin_unlock_irq(&dev->err_lock);
424    if (retval < 0)
425        goto error;
426
427    /* create a urb, and a buffer for it, and copy the data to the urb */
428    urb = usb_alloc_urb(0, GFP_KERNEL);
429    if (!urb) {
430        retval = -ENOMEM;
431        goto error;
432    }
433
434    buf = usb_alloc_coherent(dev->udev, writesize, GFP_KERNEL,
435                 &urb->transfer_dma);
436    if (!buf) {
437        retval = -ENOMEM;
438        goto error;
439    }
440
441    if (copy_from_user(buf, user_buffer, writesize)) {
442        retval = -EFAULT;
443        goto error;
444    }
445
446    /* this lock makes sure we don't submit URBs to gone devices */
447    mutex_lock(&dev->io_mutex);
448    if (!dev->interface) { /* disconnect() was called */
449        mutex_unlock(&dev->io_mutex);
450        retval = -ENODEV;
451        goto error;
452    }
453
454    /* initialize the urb properly */
455    usb_fill_bulk_urb(urb, dev->udev,
456              usb_sndbulkpipe(dev->udev, dev->bulk_out_endpointAddr),
457              buf, writesize, skel_write_bulk_callback, dev);
458    urb->transfer_flags |= URB_NO_TRANSFER_DMA_MAP;
459    usb_anchor_urb(urb, &dev->submitted);
460
461    /* send the data out the bulk port */
462    retval = usb_submit_urb(urb, GFP_KERNEL);
463    mutex_unlock(&dev->io_mutex);
464    if (retval) {
465        dev_err(&dev->interface->dev,
466            "%s - failed submitting write urb, error %d\n",
467            __func__, retval);
468        goto error_unanchor;
469    }
470
471    /*
472     * release our reference to this urb, the USB core will eventually free
473     * it entirely
474     */
475    usb_free_urb(urb);
476
477
478    return writesize;
479
480error_unanchor:
481    usb_unanchor_urb(urb);
482error:
483    if (urb) {
484        usb_free_coherent(dev->udev, writesize, buf, urb->transfer_dma);
485        usb_free_urb(urb);
486    }
487    up(&dev->limit_sem);
488
489exit:
490    return retval;
491}
492
493static const struct file_operations skel_fops = {
494    .owner = THIS_MODULE,
495    .read = skel_read,
496    .write = skel_write,
497    .open = skel_open,
498    .release = skel_release,
499    .flush = skel_flush,
500    .llseek = noop_llseek,
501};
502
503/*
504 * usb class driver info in order to get a minor number from the usb core,
505 * and to have the device registered with the driver core
506 */
507static struct usb_class_driver skel_class = {
508    .name = "skel%d",
509    .fops = &skel_fops,
510    .minor_base = USB_SKEL_MINOR_BASE,
511};
512
513static int skel_probe(struct usb_interface *interface,
514              const struct usb_device_id *id)
515{
516    struct usb_skel *dev;
517    struct usb_host_interface *iface_desc;
518    struct usb_endpoint_descriptor *endpoint;
519    size_t buffer_size;
520    int i;
521    int retval = -ENOMEM;
522
523    /* allocate memory for our device state and initialize it */
524    dev = kzalloc(sizeof(*dev), GFP_KERNEL);
525    if (!dev) {
526        dev_err(&interface->dev, "Out of memory\n");
527        goto error;
528    }
529    kref_init(&dev->kref);
530    sema_init(&dev->limit_sem, WRITES_IN_FLIGHT);
531    mutex_init(&dev->io_mutex);
532    spin_lock_init(&dev->err_lock);
533    init_usb_anchor(&dev->submitted);
534    init_completion(&dev->bulk_in_completion);
535
536    dev->udev = usb_get_dev(interface_to_usbdev(interface));
537    dev->interface = interface;
538
539    /* set up the endpoint information */
540    /* use only the first bulk-in and bulk-out endpoints */
541    iface_desc = interface->cur_altsetting;
542    for (i = 0; i < iface_desc->desc.bNumEndpoints; ++i) {
543        endpoint = &iface_desc->endpoint[i].desc;
544
545        if (!dev->bulk_in_endpointAddr &&
546            usb_endpoint_is_bulk_in(endpoint)) {
547            /* we found a bulk in endpoint */
548            buffer_size = usb_endpoint_maxp(endpoint);
549            dev->bulk_in_size = buffer_size;
550            dev->bulk_in_endpointAddr = endpoint->bEndpointAddress;
551            dev->bulk_in_buffer = kmalloc(buffer_size, GFP_KERNEL);
552            if (!dev->bulk_in_buffer) {
553                dev_err(&interface->dev,
554                    "Could not allocate bulk_in_buffer\n");
555                goto error;
556            }
557            dev->bulk_in_urb = usb_alloc_urb(0, GFP_KERNEL);
558            if (!dev->bulk_in_urb) {
559                dev_err(&interface->dev,
560                    "Could not allocate bulk_in_urb\n");
561                goto error;
562            }
563        }
564
565        if (!dev->bulk_out_endpointAddr &&
566            usb_endpoint_is_bulk_out(endpoint)) {
567            /* we found a bulk out endpoint */
568            dev->bulk_out_endpointAddr = endpoint->bEndpointAddress;
569        }
570    }
571    if (!(dev->bulk_in_endpointAddr && dev->bulk_out_endpointAddr)) {
572        dev_err(&interface->dev,
573            "Could not find both bulk-in and bulk-out endpoints\n");
574        goto error;
575    }
576
577    /* save our data pointer in this interface device */
578    usb_set_intfdata(interface, dev);
579
580    /* we can register the device now, as it is ready */
581    retval = usb_register_dev(interface, &skel_class);
582    if (retval) {
583        /* something prevented us from registering this driver */
584        dev_err(&interface->dev,
585            "Not able to get a minor for this device.\n");
586        usb_set_intfdata(interface, NULL);
587        goto error;
588    }
589
590    /* let the user know what node this device is now attached to */
591    dev_info(&interface->dev,
592         "USB Skeleton device now attached to USBSkel-%d",
593         interface->minor);
594    return 0;
595
596error:
597    if (dev)
598        /* this frees allocated memory */
599        kref_put(&dev->kref, skel_delete);
600    return retval;
601}
602
603static void skel_disconnect(struct usb_interface *interface)
604{
605    struct usb_skel *dev;
606    int minor = interface->minor;
607
608    dev = usb_get_intfdata(interface);
609    usb_set_intfdata(interface, NULL);
610
611    /* give back our minor */
612    usb_deregister_dev(interface, &skel_class);
613
614    /* prevent more I/O from starting */
615    mutex_lock(&dev->io_mutex);
616    dev->interface = NULL;
617    mutex_unlock(&dev->io_mutex);
618
619    usb_kill_anchored_urbs(&dev->submitted);
620
621    /* decrement our usage count */
622    kref_put(&dev->kref, skel_delete);
623
624    dev_info(&interface->dev, "USB Skeleton #%d now disconnected", minor);
625}
626
627static void skel_draw_down(struct usb_skel *dev)
628{
629    int time;
630
631    time = usb_wait_anchor_empty_timeout(&dev->submitted, 1000);
632    if (!time)
633        usb_kill_anchored_urbs(&dev->submitted);
634    usb_kill_urb(dev->bulk_in_urb);
635}
636
637static int skel_suspend(struct usb_interface *intf, pm_message_t message)
638{
639    struct usb_skel *dev = usb_get_intfdata(intf);
640
641    if (!dev)
642        return 0;
643    skel_draw_down(dev);
644    return 0;
645}
646
647static int skel_resume(struct usb_interface *intf)
648{
649    return 0;
650}
651
652static int skel_pre_reset(struct usb_interface *intf)
653{
654    struct usb_skel *dev = usb_get_intfdata(intf);
655
656    mutex_lock(&dev->io_mutex);
657    skel_draw_down(dev);
658
659    return 0;
660}
661
662static int skel_post_reset(struct usb_interface *intf)
663{
664    struct usb_skel *dev = usb_get_intfdata(intf);
665
666    /* we are sure no URBs are active - no locking needed */
667    dev->errors = -EPIPE;
668    mutex_unlock(&dev->io_mutex);
669
670    return 0;
671}
672
673static struct usb_driver skel_driver = {
674    .name = "skeleton",
675    .probe = skel_probe,
676    .disconnect = skel_disconnect,
677    .suspend = skel_suspend,
678    .resume = skel_resume,
679    .pre_reset = skel_pre_reset,
680    .post_reset = skel_post_reset,
681    .id_table = skel_table,
682    .supports_autosuspend = 1,
683};
684
685module_usb_driver(skel_driver);
686
687MODULE_LICENSE("GPL");
688

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