// SPDX-License-Identifier: GPL-2.0+
/*
 * kcomedilib/kcomedilib.c
 * a comedlib interface for kernel modules
 *
 * COMEDI - Linux Control and Measurement Device Interface
 * Copyright (C) 1997-2000 David A. Schleef <ds@schleef.org>
 */

#include <linux/module.h>

#include <linux/errno.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#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>
#include <linux/comedi/comedilib.h>

MODULE_AUTHOR("David Schleef <ds@schleef.org>");
MODULE_DESCRIPTION("Comedi kernel library");
MODULE_LICENSE("GPL");

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;

        if (strncmp(filename, "/dev/comedi", 11) != 0)
                return NULL;

        if (kstrtouint(filename + 11, 0, &minor))
                return NULL;

        if (minor >= COMEDI_NUM_BOARD_MINORS)
                return NULL;

        dev = comedi_dev_get_from_minor(minor);
        if (!dev)
                return NULL;

        down_read(&dev->attach_lock);
        if (dev->attached && kcomedilib_set_link_from_to(from, minor))
                retval = dev;
        else
                retval = NULL;
        up_read(&dev->attach_lock);

        if (!retval)
                comedi_dev_put(dev);

        return retval;
}
EXPORT_SYMBOL_GPL(comedi_open_from);

/**
 * 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_from);

static int comedi_do_insn(struct comedi_device *dev,
                          struct comedi_insn *insn,
                          unsigned int *data)
{
        struct comedi_subdevice *s;
        int ret;

        mutex_lock(&dev->mutex);

        if (!dev->attached) {
                ret = -EINVAL;
                goto error;
        }

        /* a subdevice instruction */
        if (insn->subdev >= dev->n_subdevices) {
                ret = -EINVAL;
                goto error;
        }
        s = &dev->subdevices[insn->subdev];

        if (s->type == COMEDI_SUBD_UNUSED) {
                dev_err(dev->class_dev,
                        "%d not usable subdevice\n", insn->subdev);
                ret = -EIO;
                goto error;
        }

        /* XXX check lock */

        ret = comedi_check_chanlist(s, 1, &insn->chanspec);
        if (ret < 0) {
                dev_err(dev->class_dev, "bad chanspec\n");
                ret = -EINVAL;
                goto error;
        }

        if (s->busy) {
                ret = -EBUSY;
                goto error;
        }
        s->busy = dev;

        switch (insn->insn) {
        case INSN_BITS:
                ret = s->insn_bits(dev, s, insn, data);
                break;
        case INSN_CONFIG:
                /* XXX should check instruction length */
                ret = s->insn_config(dev, s, insn, data);
                break;
        default:
                ret = -EINVAL;
                break;
        }

        s->busy = NULL;
error:

        mutex_unlock(&dev->mutex);
        return ret;
}

int comedi_dio_get_config(struct comedi_device *dev, unsigned int subdev,
                          unsigned int chan, unsigned int *io)
{
        struct comedi_insn insn;
        unsigned int data[2];
        int ret;

        memset(&insn, 0, sizeof(insn));
        insn.insn = INSN_CONFIG;
        insn.n = 2;
        insn.subdev = subdev;
        insn.chanspec = CR_PACK(chan, 0, 0);
        data[0] = INSN_CONFIG_DIO_QUERY;
        data[1] = 0;
        ret = comedi_do_insn(dev, &insn, data);
        if (ret >= 0)
                *io = data[1];
        return ret;
}
EXPORT_SYMBOL_GPL(comedi_dio_get_config);

int comedi_dio_config(struct comedi_device *dev, unsigned int subdev,
                      unsigned int chan, unsigned int io)
{
        struct comedi_insn insn;

        memset(&insn, 0, sizeof(insn));
        insn.insn = INSN_CONFIG;
        insn.n = 1;
        insn.subdev = subdev;
        insn.chanspec = CR_PACK(chan, 0, 0);

        return comedi_do_insn(dev, &insn, &io);
}
EXPORT_SYMBOL_GPL(comedi_dio_config);

int comedi_dio_bitfield2(struct comedi_device *dev, unsigned int subdev,
                         unsigned int mask, unsigned int *bits,
                         unsigned int base_channel)
{
        struct comedi_insn insn;
        unsigned int data[2];
        unsigned int n_chan;
        unsigned int shift;
        int ret;

        base_channel = CR_CHAN(base_channel);
        n_chan = comedi_get_n_channels(dev, subdev);
        if (base_channel >= n_chan)
                return -EINVAL;

        memset(&insn, 0, sizeof(insn));
        insn.insn = INSN_BITS;
        insn.chanspec = base_channel;
        insn.n = 2;
        insn.subdev = subdev;

        data[0] = mask;
        data[1] = *bits;

        /*
         * Most drivers ignore the base channel in insn->chanspec.
         * Fix this here if the subdevice has <= 32 channels.
         */
        if (n_chan <= 32) {
                shift = base_channel;
                if (shift) {
                        insn.chanspec = 0;
                        data[0] <<= shift;
                        data[1] <<= shift;
                }
        } else {
                shift = 0;
        }

        ret = comedi_do_insn(dev, &insn, data);
        *bits = data[1] >> shift;
        return ret;
}
EXPORT_SYMBOL_GPL(comedi_dio_bitfield2);

int comedi_find_subdevice_by_type(struct comedi_device *dev, int type,
                                  unsigned int subd)
{
        struct comedi_subdevice *s;
        int ret = -ENODEV;

        down_read(&dev->attach_lock);
        if (dev->attached)
                for (; subd < dev->n_subdevices; subd++) {
                        s = &dev->subdevices[subd];
                        if (s->type == type) {
                                ret = subd;
                                break;
                        }
                }
        up_read(&dev->attach_lock);
        return ret;
}
EXPORT_SYMBOL_GPL(comedi_find_subdevice_by_type);

int comedi_get_n_channels(struct comedi_device *dev, unsigned int subdevice)
{
        int n;

        down_read(&dev->attach_lock);
        if (!dev->attached || subdevice >= dev->n_subdevices)
                n = 0;
        else
                n = dev->subdevices[subdevice].n_chan;
        up_read(&dev->attach_lock);

        return n;
}
EXPORT_SYMBOL_GPL(comedi_get_n_channels);

static int __init kcomedilib_module_init(void)
{
        return 0;
}

static void __exit kcomedilib_module_exit(void)
{
}

module_init(kcomedilib_module_init);
module_exit(kcomedilib_module_exit);