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584 lines
13 KiB
584 lines
13 KiB
// SPDX-License-Identifier: GPL-2.0 |
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/* |
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* chaoskey - driver for ChaosKey device from Altus Metrum. |
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* |
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* This device provides true random numbers using a noise source based |
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* on a reverse-biased p-n junction in avalanche breakdown. More |
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* details can be found at http://chaoskey.org |
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* |
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* The driver connects to the kernel hardware RNG interface to provide |
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* entropy for /dev/random and other kernel activities. It also offers |
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* a separate /dev/ entry to allow for direct access to the random |
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* bit stream. |
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* |
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* Copyright © 2015 Keith Packard <[email protected]> |
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*/ |
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|
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#include <linux/module.h> |
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#include <linux/slab.h> |
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#include <linux/usb.h> |
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#include <linux/wait.h> |
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#include <linux/hw_random.h> |
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#include <linux/mutex.h> |
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#include <linux/uaccess.h> |
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|
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static struct usb_driver chaoskey_driver; |
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static struct usb_class_driver chaoskey_class; |
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static int chaoskey_rng_read(struct hwrng *rng, void *data, |
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size_t max, bool wait); |
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|
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#define usb_dbg(usb_if, format, arg...) \ |
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dev_dbg(&(usb_if)->dev, format, ## arg) |
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|
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#define usb_err(usb_if, format, arg...) \ |
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dev_err(&(usb_if)->dev, format, ## arg) |
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|
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/* Version Information */ |
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#define DRIVER_AUTHOR "Keith Packard, [email protected]" |
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#define DRIVER_DESC "Altus Metrum ChaosKey driver" |
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#define DRIVER_SHORT "chaoskey" |
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|
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MODULE_AUTHOR(DRIVER_AUTHOR); |
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MODULE_DESCRIPTION(DRIVER_DESC); |
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MODULE_LICENSE("GPL"); |
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|
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#define CHAOSKEY_VENDOR_ID 0x1d50 /* OpenMoko */ |
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#define CHAOSKEY_PRODUCT_ID 0x60c6 /* ChaosKey */ |
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|
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#define ALEA_VENDOR_ID 0x12d8 /* Araneus */ |
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#define ALEA_PRODUCT_ID 0x0001 /* Alea I */ |
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|
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#define CHAOSKEY_BUF_LEN 64 /* max size of USB full speed packet */ |
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|
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#define NAK_TIMEOUT (HZ) /* normal stall/wait timeout */ |
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#define ALEA_FIRST_TIMEOUT (HZ*3) /* first stall/wait timeout for Alea */ |
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|
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#ifdef CONFIG_USB_DYNAMIC_MINORS |
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#define USB_CHAOSKEY_MINOR_BASE 0 |
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#else |
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|
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/* IOWARRIOR_MINOR_BASE + 16, not official yet */ |
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#define USB_CHAOSKEY_MINOR_BASE 224 |
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#endif |
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|
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static const struct usb_device_id chaoskey_table[] = { |
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{ USB_DEVICE(CHAOSKEY_VENDOR_ID, CHAOSKEY_PRODUCT_ID) }, |
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{ USB_DEVICE(ALEA_VENDOR_ID, ALEA_PRODUCT_ID) }, |
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{ }, |
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}; |
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MODULE_DEVICE_TABLE(usb, chaoskey_table); |
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|
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static void chaos_read_callback(struct urb *urb); |
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|
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/* Driver-local specific stuff */ |
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struct chaoskey { |
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struct usb_interface *interface; |
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char in_ep; |
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struct mutex lock; |
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struct mutex rng_lock; |
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int open; /* open count */ |
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bool present; /* device not disconnected */ |
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bool reading; /* ongoing IO */ |
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bool reads_started; /* track first read for Alea */ |
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int size; /* size of buf */ |
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int valid; /* bytes of buf read */ |
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int used; /* bytes of buf consumed */ |
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char *name; /* product + serial */ |
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struct hwrng hwrng; /* Embedded struct for hwrng */ |
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int hwrng_registered; /* registered with hwrng API */ |
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wait_queue_head_t wait_q; /* for timeouts */ |
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struct urb *urb; /* for performing IO */ |
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char *buf; |
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}; |
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|
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static void chaoskey_free(struct chaoskey *dev) |
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{ |
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if (dev) { |
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usb_dbg(dev->interface, "free"); |
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usb_free_urb(dev->urb); |
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kfree(dev->name); |
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kfree(dev->buf); |
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usb_put_intf(dev->interface); |
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kfree(dev); |
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} |
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} |
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|
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static int chaoskey_probe(struct usb_interface *interface, |
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const struct usb_device_id *id) |
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{ |
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struct usb_device *udev = interface_to_usbdev(interface); |
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struct usb_host_interface *altsetting = interface->cur_altsetting; |
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struct usb_endpoint_descriptor *epd; |
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int in_ep; |
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struct chaoskey *dev; |
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int result = -ENOMEM; |
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int size; |
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int res; |
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|
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usb_dbg(interface, "probe %s-%s", udev->product, udev->serial); |
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|
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/* Find the first bulk IN endpoint and its packet size */ |
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res = usb_find_bulk_in_endpoint(altsetting, &epd); |
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if (res) { |
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usb_dbg(interface, "no IN endpoint found"); |
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return res; |
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} |
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|
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in_ep = usb_endpoint_num(epd); |
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size = usb_endpoint_maxp(epd); |
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|
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/* Validate endpoint and size */ |
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if (size <= 0) { |
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usb_dbg(interface, "invalid size (%d)", size); |
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return -ENODEV; |
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} |
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|
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if (size > CHAOSKEY_BUF_LEN) { |
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usb_dbg(interface, "size reduced from %d to %d\n", |
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size, CHAOSKEY_BUF_LEN); |
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size = CHAOSKEY_BUF_LEN; |
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} |
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|
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/* Looks good, allocate and initialize */ |
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|
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dev = kzalloc(sizeof(struct chaoskey), GFP_KERNEL); |
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|
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if (dev == NULL) |
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goto out; |
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|
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dev->interface = usb_get_intf(interface); |
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dev->buf = kmalloc(size, GFP_KERNEL); |
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|
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if (dev->buf == NULL) |
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goto out; |
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dev->urb = usb_alloc_urb(0, GFP_KERNEL); |
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|
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if (!dev->urb) |
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goto out; |
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|
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usb_fill_bulk_urb(dev->urb, |
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udev, |
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usb_rcvbulkpipe(udev, in_ep), |
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dev->buf, |
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size, |
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chaos_read_callback, |
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dev); |
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|
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/* Construct a name using the product and serial values. Each |
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* device needs a unique name for the hwrng code |
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*/ |
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|
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if (udev->product && udev->serial) { |
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dev->name = kasprintf(GFP_KERNEL, "%s-%s", udev->product, |
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udev->serial); |
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if (dev->name == NULL) |
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goto out; |
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} |
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dev->in_ep = in_ep; |
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|
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if (le16_to_cpu(udev->descriptor.idVendor) != ALEA_VENDOR_ID) |
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dev->reads_started = true; |
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dev->size = size; |
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dev->present = true; |
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init_waitqueue_head(&dev->wait_q); |
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|
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mutex_init(&dev->lock); |
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mutex_init(&dev->rng_lock); |
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usb_set_intfdata(interface, dev); |
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|
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result = usb_register_dev(interface, &chaoskey_class); |
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if (result) { |
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usb_err(interface, "Unable to allocate minor number."); |
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goto out; |
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} |
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dev->hwrng.name = dev->name ? dev->name : chaoskey_driver.name; |
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dev->hwrng.read = chaoskey_rng_read; |
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dev->hwrng.quality = 1024; |
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dev->hwrng_registered = (hwrng_register(&dev->hwrng) == 0); |
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if (!dev->hwrng_registered) |
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usb_err(interface, "Unable to register with hwrng"); |
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usb_enable_autosuspend(udev); |
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usb_dbg(interface, "chaoskey probe success, size %d", dev->size); |
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return 0; |
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out: |
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usb_set_intfdata(interface, NULL); |
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chaoskey_free(dev); |
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return result; |
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} |
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static void chaoskey_disconnect(struct usb_interface *interface) |
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{ |
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struct chaoskey *dev; |
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usb_dbg(interface, "disconnect"); |
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dev = usb_get_intfdata(interface); |
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if (!dev) { |
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usb_dbg(interface, "disconnect failed - no dev"); |
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return; |
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} |
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if (dev->hwrng_registered) |
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hwrng_unregister(&dev->hwrng); |
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usb_deregister_dev(interface, &chaoskey_class); |
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usb_set_intfdata(interface, NULL); |
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mutex_lock(&dev->lock); |
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dev->present = false; |
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usb_poison_urb(dev->urb); |
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|
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if (!dev->open) { |
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mutex_unlock(&dev->lock); |
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chaoskey_free(dev); |
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} else |
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mutex_unlock(&dev->lock); |
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usb_dbg(interface, "disconnect done"); |
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} |
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static int chaoskey_open(struct inode *inode, struct file *file) |
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{ |
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struct chaoskey *dev; |
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struct usb_interface *interface; |
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|
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/* get the interface from minor number and driver information */ |
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interface = usb_find_interface(&chaoskey_driver, iminor(inode)); |
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if (!interface) |
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return -ENODEV; |
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usb_dbg(interface, "open"); |
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dev = usb_get_intfdata(interface); |
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if (!dev) { |
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usb_dbg(interface, "open (dev)"); |
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return -ENODEV; |
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} |
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file->private_data = dev; |
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mutex_lock(&dev->lock); |
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++dev->open; |
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mutex_unlock(&dev->lock); |
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usb_dbg(interface, "open success"); |
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return 0; |
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} |
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static int chaoskey_release(struct inode *inode, struct file *file) |
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{ |
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struct chaoskey *dev = file->private_data; |
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struct usb_interface *interface; |
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if (dev == NULL) |
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return -ENODEV; |
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interface = dev->interface; |
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usb_dbg(interface, "release"); |
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mutex_lock(&dev->lock); |
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usb_dbg(interface, "open count at release is %d", dev->open); |
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if (dev->open <= 0) { |
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usb_dbg(interface, "invalid open count (%d)", dev->open); |
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mutex_unlock(&dev->lock); |
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return -ENODEV; |
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} |
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--dev->open; |
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if (!dev->present) { |
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if (dev->open == 0) { |
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mutex_unlock(&dev->lock); |
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chaoskey_free(dev); |
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} else |
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mutex_unlock(&dev->lock); |
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} else |
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mutex_unlock(&dev->lock); |
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usb_dbg(interface, "release success"); |
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return 0; |
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} |
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static void chaos_read_callback(struct urb *urb) |
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{ |
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struct chaoskey *dev = urb->context; |
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int status = urb->status; |
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usb_dbg(dev->interface, "callback status (%d)", status); |
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if (status == 0) |
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dev->valid = urb->actual_length; |
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else |
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dev->valid = 0; |
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dev->used = 0; |
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/* must be seen first before validity is announced */ |
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smp_wmb(); |
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dev->reading = false; |
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wake_up(&dev->wait_q); |
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} |
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|
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/* Fill the buffer. Called with dev->lock held |
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*/ |
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static int _chaoskey_fill(struct chaoskey *dev) |
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{ |
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DEFINE_WAIT(wait); |
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int result; |
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bool started; |
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usb_dbg(dev->interface, "fill"); |
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|
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/* Return immediately if someone called before the buffer was |
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* empty */ |
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if (dev->valid != dev->used) { |
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usb_dbg(dev->interface, "not empty yet (valid %d used %d)", |
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dev->valid, dev->used); |
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return 0; |
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} |
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|
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/* Bail if the device has been removed */ |
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if (!dev->present) { |
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usb_dbg(dev->interface, "device not present"); |
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return -ENODEV; |
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} |
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|
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/* Make sure the device is awake */ |
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result = usb_autopm_get_interface(dev->interface); |
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if (result) { |
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usb_dbg(dev->interface, "wakeup failed (result %d)", result); |
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return result; |
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} |
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|
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dev->reading = true; |
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result = usb_submit_urb(dev->urb, GFP_KERNEL); |
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if (result < 0) { |
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result = usb_translate_errors(result); |
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dev->reading = false; |
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goto out; |
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} |
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|
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/* The first read on the Alea takes a little under 2 seconds. |
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* Reads after the first read take only a few microseconds |
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* though. Presumably the entropy-generating circuit needs |
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* time to ramp up. So, we wait longer on the first read. |
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*/ |
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started = dev->reads_started; |
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dev->reads_started = true; |
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result = wait_event_interruptible_timeout( |
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dev->wait_q, |
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!dev->reading, |
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(started ? NAK_TIMEOUT : ALEA_FIRST_TIMEOUT) ); |
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|
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if (result < 0) { |
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usb_kill_urb(dev->urb); |
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goto out; |
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} |
|
|
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if (result == 0) { |
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result = -ETIMEDOUT; |
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usb_kill_urb(dev->urb); |
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} else { |
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result = dev->valid; |
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} |
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out: |
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/* Let the device go back to sleep eventually */ |
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usb_autopm_put_interface(dev->interface); |
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|
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usb_dbg(dev->interface, "read %d bytes", dev->valid); |
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|
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return result; |
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} |
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|
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static ssize_t chaoskey_read(struct file *file, |
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char __user *buffer, |
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size_t count, |
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loff_t *ppos) |
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{ |
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struct chaoskey *dev; |
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ssize_t read_count = 0; |
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int this_time; |
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int result = 0; |
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unsigned long remain; |
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|
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dev = file->private_data; |
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|
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if (dev == NULL || !dev->present) |
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return -ENODEV; |
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|
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usb_dbg(dev->interface, "read %zu", count); |
|
|
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while (count > 0) { |
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|
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/* Grab the rng_lock briefly to ensure that the hwrng interface |
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* gets priority over other user access |
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*/ |
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result = mutex_lock_interruptible(&dev->rng_lock); |
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if (result) |
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goto bail; |
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mutex_unlock(&dev->rng_lock); |
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|
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result = mutex_lock_interruptible(&dev->lock); |
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if (result) |
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goto bail; |
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if (dev->valid == dev->used) { |
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result = _chaoskey_fill(dev); |
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if (result < 0) { |
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mutex_unlock(&dev->lock); |
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goto bail; |
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} |
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} |
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|
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this_time = dev->valid - dev->used; |
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if (this_time > count) |
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this_time = count; |
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|
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remain = copy_to_user(buffer, dev->buf + dev->used, this_time); |
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if (remain) { |
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result = -EFAULT; |
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|
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/* Consume the bytes that were copied so we don't leak |
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* data to user space |
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*/ |
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dev->used += this_time - remain; |
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mutex_unlock(&dev->lock); |
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goto bail; |
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} |
|
|
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count -= this_time; |
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read_count += this_time; |
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buffer += this_time; |
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dev->used += this_time; |
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mutex_unlock(&dev->lock); |
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} |
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bail: |
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if (read_count) { |
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usb_dbg(dev->interface, "read %zu bytes", read_count); |
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return read_count; |
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} |
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usb_dbg(dev->interface, "empty read, result %d", result); |
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if (result == -ETIMEDOUT) |
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result = -EAGAIN; |
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return result; |
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} |
|
|
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static int chaoskey_rng_read(struct hwrng *rng, void *data, |
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size_t max, bool wait) |
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{ |
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struct chaoskey *dev = container_of(rng, struct chaoskey, hwrng); |
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int this_time; |
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|
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usb_dbg(dev->interface, "rng_read max %zu wait %d", max, wait); |
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|
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if (!dev->present) { |
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usb_dbg(dev->interface, "device not present"); |
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return 0; |
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} |
|
|
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/* Hold the rng_lock until we acquire the device lock so that |
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* this operation gets priority over other user access to the |
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* device |
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*/ |
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mutex_lock(&dev->rng_lock); |
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|
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mutex_lock(&dev->lock); |
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|
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mutex_unlock(&dev->rng_lock); |
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|
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/* Try to fill the buffer if empty. It doesn't actually matter |
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* if _chaoskey_fill works; we'll just return zero bytes as |
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* the buffer will still be empty |
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*/ |
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if (dev->valid == dev->used) |
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(void) _chaoskey_fill(dev); |
|
|
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this_time = dev->valid - dev->used; |
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if (this_time > max) |
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this_time = max; |
|
|
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memcpy(data, dev->buf + dev->used, this_time); |
|
|
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dev->used += this_time; |
|
|
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mutex_unlock(&dev->lock); |
|
|
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usb_dbg(dev->interface, "rng_read this_time %d\n", this_time); |
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return this_time; |
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} |
|
|
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#ifdef CONFIG_PM |
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static int chaoskey_suspend(struct usb_interface *interface, |
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pm_message_t message) |
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{ |
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usb_dbg(interface, "suspend"); |
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return 0; |
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} |
|
|
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static int chaoskey_resume(struct usb_interface *interface) |
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{ |
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struct chaoskey *dev; |
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struct usb_device *udev = interface_to_usbdev(interface); |
|
|
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usb_dbg(interface, "resume"); |
|
dev = usb_get_intfdata(interface); |
|
|
|
/* |
|
* We may have lost power. |
|
* In that case the device that needs a long time |
|
* for the first requests needs an extended timeout |
|
* again |
|
*/ |
|
if (le16_to_cpu(udev->descriptor.idVendor) == ALEA_VENDOR_ID) |
|
dev->reads_started = false; |
|
|
|
return 0; |
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} |
|
#else |
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#define chaoskey_suspend NULL |
|
#define chaoskey_resume NULL |
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#endif |
|
|
|
/* file operation pointers */ |
|
static const struct file_operations chaoskey_fops = { |
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.owner = THIS_MODULE, |
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.read = chaoskey_read, |
|
.open = chaoskey_open, |
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.release = chaoskey_release, |
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.llseek = default_llseek, |
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}; |
|
|
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/* class driver information */ |
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static struct usb_class_driver chaoskey_class = { |
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.name = "chaoskey%d", |
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.fops = &chaoskey_fops, |
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.minor_base = USB_CHAOSKEY_MINOR_BASE, |
|
}; |
|
|
|
/* usb specific object needed to register this driver with the usb subsystem */ |
|
static struct usb_driver chaoskey_driver = { |
|
.name = DRIVER_SHORT, |
|
.probe = chaoskey_probe, |
|
.disconnect = chaoskey_disconnect, |
|
.suspend = chaoskey_suspend, |
|
.resume = chaoskey_resume, |
|
.reset_resume = chaoskey_resume, |
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.id_table = chaoskey_table, |
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.supports_autosuspend = 1, |
|
}; |
|
|
|
module_usb_driver(chaoskey_driver); |
|
|
|
|