diff options
Diffstat (limited to 'drivers/comedi/kcomedilib/kcomedilib_main.c')
| -rw-r--r-- | drivers/comedi/kcomedilib/kcomedilib_main.c | 120 |
1 files changed, 115 insertions, 5 deletions
diff --git a/drivers/comedi/kcomedilib/kcomedilib_main.c b/drivers/comedi/kcomedilib/kcomedilib_main.c index 43fbe1a63b14..baa9eaaf97d4 100644 --- a/drivers/comedi/kcomedilib/kcomedilib_main.c +++ b/drivers/comedi/kcomedilib/kcomedilib_main.c @@ -15,6 +15,7 @@ #include <linux/fcntl.h> #include <linux/mm.h> #include <linux/io.h> +#include <linux/bitmap.h> #include <linux/comedi.h> #include <linux/comedi/comedidev.h> @@ -24,7 +25,104 @@ MODULE_AUTHOR("David Schleef <ds@schleef.org>"); MODULE_DESCRIPTION("Comedi kernel library"); MODULE_LICENSE("GPL"); -struct comedi_device *comedi_open(const char *filename) +static DEFINE_MUTEX(kcomedilib_to_from_lock); + +/* + * Row index is the "to" node, column index is the "from" node, element value + * is the number of links from the "from" node to the "to" node. + */ +static unsigned char + kcomedilib_to_from[COMEDI_NUM_BOARD_MINORS][COMEDI_NUM_BOARD_MINORS]; + +static bool kcomedilib_set_link_from_to(unsigned int from, unsigned int to) +{ + DECLARE_BITMAP(destinations[2], COMEDI_NUM_BOARD_MINORS); + unsigned int cur = 0; + bool okay = true; + + /* + * Allow "from" node to be out of range (no loop checking), + * but require "to" node to be in range. + */ + if (to >= COMEDI_NUM_BOARD_MINORS) + return false; + if (from >= COMEDI_NUM_BOARD_MINORS) + return true; + + /* + * Check that kcomedilib_to_from[to][from] can be made non-zero + * without creating a loop. + * + * Termination of the loop-testing code relies on the assumption that + * kcomedilib_to_from[][] does not contain any loops. + * + * Start with a set destinations set containing "from" as the only + * element and work backwards looking for loops. + */ + bitmap_zero(destinations[cur], COMEDI_NUM_BOARD_MINORS); + set_bit(from, destinations[cur]); + mutex_lock(&kcomedilib_to_from_lock); + do { + unsigned int next = 1 - cur; + unsigned int t = 0; + + if (test_bit(to, destinations[cur])) { + /* Loop detected. */ + okay = false; + break; + } + /* Create next set of destinations. */ + bitmap_zero(destinations[next], COMEDI_NUM_BOARD_MINORS); + while ((t = find_next_bit(destinations[cur], + COMEDI_NUM_BOARD_MINORS, + t)) < COMEDI_NUM_BOARD_MINORS) { + unsigned int f; + + for (f = 0; f < COMEDI_NUM_BOARD_MINORS; f++) { + if (kcomedilib_to_from[t][f]) + set_bit(f, destinations[next]); + } + t++; + } + cur = next; + } while (!bitmap_empty(destinations[cur], COMEDI_NUM_BOARD_MINORS)); + if (okay) { + /* Allow a maximum of 255 links from "from" to "to". */ + if (kcomedilib_to_from[to][from] < 255) + kcomedilib_to_from[to][from]++; + else + okay = false; + } + mutex_unlock(&kcomedilib_to_from_lock); + return okay; +} + +static void kcomedilib_clear_link_from_to(unsigned int from, unsigned int to) +{ + if (to < COMEDI_NUM_BOARD_MINORS && from < COMEDI_NUM_BOARD_MINORS) { + mutex_lock(&kcomedilib_to_from_lock); + if (kcomedilib_to_from[to][from]) + kcomedilib_to_from[to][from]--; + mutex_unlock(&kcomedilib_to_from_lock); + } +} + +/** + * comedi_open_from() - Open a COMEDI device from the kernel with loop checks + * @filename: Fake pathname of the form "/dev/comediN". + * @from: Device number it is being opened from (if in range). + * + * Converts @filename to a COMEDI device number and "opens" it if it exists + * and is attached to a low-level COMEDI driver. + * + * If @from is in range, refuse to open the device if doing so would form a + * loop of devices opening each other. There is also a limit of 255 on the + * number of concurrent opens from one device to another. + * + * Return: A pointer to the COMEDI device on success. + * Return %NULL on failure. + */ +struct comedi_device *comedi_open_from(const char *filename, int from) { struct comedi_device *dev, *retval = NULL; unsigned int minor; @@ -43,7 +141,7 @@ struct comedi_device *comedi_open(const char *filename) return NULL; down_read(&dev->attach_lock); - if (dev->attached) + if (dev->attached && kcomedilib_set_link_from_to(from, minor)) retval = dev; else retval = NULL; @@ -54,14 +152,26 @@ struct comedi_device *comedi_open(const char *filename) return retval; } -EXPORT_SYMBOL_GPL(comedi_open); +EXPORT_SYMBOL_GPL(comedi_open_from); -int comedi_close(struct comedi_device *dev) +/** + * comedi_close_from() - Close a COMEDI device from the kernel with loop checks + * @dev: COMEDI device. + * @from: Device number it was opened from (if in range). + * + * Closes a COMEDI device previously opened by comedi_open_from(). + * + * If @from is in range, it should be match the one used by comedi_open_from(). + * + * Returns: 0 + */ +int comedi_close_from(struct comedi_device *dev, int from) { + kcomedilib_clear_link_from_to(from, dev->minor); comedi_dev_put(dev); return 0; } -EXPORT_SYMBOL_GPL(comedi_close); +EXPORT_SYMBOL_GPL(comedi_close_from); static int comedi_do_insn(struct comedi_device *dev, struct comedi_insn *insn, |