// SPDX-License-Identifier: GPL-2.0+
/*
 * comedi/drivers/comedi_test.c
 *
 * Generates fake waveform signals that can be read through
 * the command interface.  It does _not_ read from any board;
 * it just generates deterministic waveforms.
 * Useful for various testing purposes.
 *
 * Copyright (C) 2002 Joachim Wuttke <Joachim.Wuttke@icn.siemens.de>
 * Copyright (C) 2002 Frank Mori Hess <fmhess@users.sourceforge.net>
 *
 * COMEDI - Linux Control and Measurement Device Interface
 * Copyright (C) 2000 David A. Schleef <ds@schleef.org>
 */

/*
 * Driver: comedi_test
 * Description: generates fake waveforms
 * Author: Joachim Wuttke <Joachim.Wuttke@icn.siemens.de>, Frank Mori Hess
 *   <fmhess@users.sourceforge.net>, ds
 * Devices:
 * Status: works
 * Updated: Sat, 16 Mar 2002 17:34:48 -0800
 *
 * This driver is mainly for testing purposes, but can also be used to
 * generate sample waveforms on systems that don't have data acquisition
 * hardware.
 *
 * Auto-configuration is the default mode if no parameter is supplied during
 * module loading. Manual configuration requires COMEDI userspace tool.
 * To disable auto-configuration mode, pass "noauto=1" parameter for module
 * loading. Refer modinfo or MODULE_PARM_DESC description below for details.
 *
 * Auto-configuration options:
 *   Refer modinfo or MODULE_PARM_DESC description below for details.
 *
 * Manual configuration options:
 *   [0] - Amplitude in microvolts for fake waveforms (default 1 volt)
 *   [1] - Period in microseconds for fake waveforms (default 0.1 sec)
 *
 * Generates a sawtooth wave on channel 0, square wave on channel 1, additional
 * waveforms could be added to other channels (currently they return flatline
 * zero volts).
 */

#include <linux/module.h>
#include "../comedidev.h"

#include <asm/div64.h>

#include <linux/timer.h>
#include <linux/ktime.h>
#include <linux/jiffies.h>
#include <linux/device.h>
#include <linux/kdev_t.h>

#define N_CHANS 8
#define DEV_NAME "comedi_testd"
#define CLASS_NAME "comedi_test"

static bool config_mode;
static unsigned int set_amplitude;
static unsigned int set_period;
static struct class *ctcls;
static struct device *ctdev;

module_param_named(noauto, config_mode, bool, 0444);
MODULE_PARM_DESC(noauto, "Disable auto-configuration: (1=disable [defaults to enable])");

module_param_named(amplitude, set_amplitude, uint, 0444);
MODULE_PARM_DESC(amplitude, "Set auto mode wave amplitude in microvolts: (defaults to 1 volt)");

module_param_named(period, set_period, uint, 0444);
MODULE_PARM_DESC(period, "Set auto mode wave period in microseconds: (defaults to 0.1 sec)");

/* Data unique to this driver */
struct waveform_private {
        struct timer_list ai_timer;     /* timer for AI commands */
        u64 ai_convert_time;            /* time of next AI conversion in usec */
        unsigned int wf_amplitude;      /* waveform amplitude in microvolts */
        unsigned int wf_period;         /* waveform period in microseconds */
        unsigned int wf_current;        /* current time in waveform period */
        unsigned int ai_scan_period;    /* AI scan period in usec */
        unsigned int ai_convert_period; /* AI conversion period in usec */
        struct timer_list ao_timer;     /* timer for AO commands */
        struct comedi_device *dev;      /* parent comedi device */
        u64 ao_last_scan_time;          /* time of previous AO scan in usec */
        unsigned int ao_scan_period;    /* AO scan period in usec */
        unsigned short ao_loopbacks[N_CHANS];
};

/* fake analog input ranges */
static const struct comedi_lrange waveform_ai_ranges = {
        2, {
                BIP_RANGE(10),
                BIP_RANGE(5)
        }
};

static unsigned short fake_sawtooth(struct comedi_device *dev,
                                    unsigned int range_index,
                                    unsigned int current_time)
{
        struct waveform_private *devpriv = dev->private;
        struct comedi_subdevice *s = dev->read_subdev;
        unsigned int offset = s->maxdata / 2;
        u64 value;
        const struct comedi_krange *krange =
            &s->range_table->range[range_index];
        u64 binary_amplitude;

        binary_amplitude = s->maxdata;
        binary_amplitude *= devpriv->wf_amplitude;
        do_div(binary_amplitude, krange->max - krange->min);

        value = current_time;
        value *= binary_amplitude * 2;
        do_div(value, devpriv->wf_period);
        value += offset;
        /* get rid of sawtooth's dc offset and clamp value */
        if (value < binary_amplitude) {
                value = 0;                      /* negative saturation */
        } else {
                value -= binary_amplitude;
                if (value > s->maxdata)
                        value = s->maxdata;     /* positive saturation */
        }

        return value;
}

static unsigned short fake_squarewave(struct comedi_device *dev,
                                      unsigned int range_index,
                                      unsigned int current_time)
{
        struct waveform_private *devpriv = dev->private;
        struct comedi_subdevice *s = dev->read_subdev;
        unsigned int offset = s->maxdata / 2;
        u64 value;
        const struct comedi_krange *krange =
            &s->range_table->range[range_index];

        value = s->maxdata;
        value *= devpriv->wf_amplitude;
        do_div(value, krange->max - krange->min);

        /* get one of two values for square-wave and clamp */
        if (current_time < devpriv->wf_period / 2) {
                if (offset < value)
                        value = 0;              /* negative saturation */
                else
                        value = offset - value;
        } else {
                value += offset;
                if (value > s->maxdata)
                        value = s->maxdata;     /* positive saturation */
        }

        return value;
}

static unsigned short fake_flatline(struct comedi_device *dev,
                                    unsigned int range_index,
                                    unsigned int current_time)
{
        return dev->read_subdev->maxdata / 2;
}

/* generates a different waveform depending on what channel is read */
static unsigned short fake_waveform(struct comedi_device *dev,
                                    unsigned int channel, unsigned int range,
                                    unsigned int current_time)
{
        enum {
                SAWTOOTH_CHAN,
                SQUARE_CHAN,
        };
        switch (channel) {
        case SAWTOOTH_CHAN:
                return fake_sawtooth(dev, range, current_time);
        case SQUARE_CHAN:
                return fake_squarewave(dev, range, current_time);
        default:
                break;
        }

        return fake_flatline(dev, range, current_time);
}

/*
 * This is the background routine used to generate arbitrary data.
 * It should run in the background; therefore it is scheduled by
 * a timer mechanism.
 */
static void waveform_ai_timer(struct timer_list *t)
{
        struct waveform_private *devpriv = from_timer(devpriv, t, ai_timer);
        struct comedi_device *dev = devpriv->dev;
        struct comedi_subdevice *s = dev->read_subdev;
        struct comedi_async *async = s->async;
        struct comedi_cmd *cmd = &async->cmd;
        u64 now;
        unsigned int nsamples;
        unsigned int time_increment;

        now = ktime_to_us(ktime_get());
        nsamples = comedi_nsamples_left(s, UINT_MAX);

        while (nsamples && devpriv->ai_convert_time < now) {
                unsigned int chanspec = cmd->chanlist[async->cur_chan];
                unsigned short sample;

                sample = fake_waveform(dev, CR_CHAN(chanspec),
                                       CR_RANGE(chanspec), devpriv->wf_current);
                if (comedi_buf_write_samples(s, &sample, 1) == 0)
                        goto overrun;
                time_increment = devpriv->ai_convert_period;
                if (async->scan_progress == 0) {
                        /* done last conversion in scan, so add dead time */
                        time_increment += devpriv->ai_scan_period -
                                          devpriv->ai_convert_period *
                                          cmd->scan_end_arg;
                }
                devpriv->wf_current += time_increment;
                if (devpriv->wf_current >= devpriv->wf_period)
                        devpriv->wf_current %= devpriv->wf_period;
                devpriv->ai_convert_time += time_increment;
                nsamples--;
        }

        if (cmd->stop_src == TRIG_COUNT && async->scans_done >= cmd->stop_arg) {
                async->events |= COMEDI_CB_EOA;
        } else {
                if (devpriv->ai_convert_time > now)
                        time_increment = devpriv->ai_convert_time - now;
                else
                        time_increment = 1;
                mod_timer(&devpriv->ai_timer,
                          jiffies + usecs_to_jiffies(time_increment));
        }

overrun:
        comedi_handle_events(dev, s);
}

static int waveform_ai_cmdtest(struct comedi_device *dev,
                               struct comedi_subdevice *s,
                               struct comedi_cmd *cmd)
{
        int err = 0;
        unsigned int arg, limit;

        /* Step 1 : check if triggers are trivially valid */

        err |= comedi_check_trigger_src(&cmd->start_src, TRIG_NOW);
        err |= comedi_check_trigger_src(&cmd->scan_begin_src,
                                        TRIG_FOLLOW | TRIG_TIMER);
        err |= comedi_check_trigger_src(&cmd->convert_src,
                                        TRIG_NOW | TRIG_TIMER);
        err |= comedi_check_trigger_src(&cmd->scan_end_src, TRIG_COUNT);
        err |= comedi_check_trigger_src(&cmd->stop_src, TRIG_COUNT | TRIG_NONE);

        if (err)
                return 1;

        /* Step 2a : make sure trigger sources are unique */

        err |= comedi_check_trigger_is_unique(cmd->convert_src);
        err |= comedi_check_trigger_is_unique(cmd->stop_src);

        /* Step 2b : and mutually compatible */

        if (cmd->scan_begin_src == TRIG_FOLLOW && cmd->convert_src == TRIG_NOW)
                err |= -EINVAL;         /* scan period would be 0 */

        if (err)
                return 2;

        /* Step 3: check if arguments are trivially valid */

        err |= comedi_check_trigger_arg_is(&cmd->start_arg, 0);

        if (cmd->convert_src == TRIG_NOW) {
                err |= comedi_check_trigger_arg_is(&cmd->convert_arg, 0);
        } else {        /* cmd->convert_src == TRIG_TIMER */
                if (cmd->scan_begin_src == TRIG_FOLLOW) {
                        err |= comedi_check_trigger_arg_min(&cmd->convert_arg,
                                                            NSEC_PER_USEC);
                }
        }

        if (cmd->scan_begin_src == TRIG_FOLLOW) {
                err |= comedi_check_trigger_arg_is(&cmd->scan_begin_arg, 0);
        } else {        /* cmd->scan_begin_src == TRIG_TIMER */
                err |= comedi_check_trigger_arg_min(&cmd->scan_begin_arg,
                                                    NSEC_PER_USEC);
        }

        err |= comedi_check_trigger_arg_min(&cmd->chanlist_len, 1);
        err |= comedi_check_trigger_arg_is(&cmd->scan_end_arg,
                                           cmd->chanlist_len);

        if (cmd->stop_src == TRIG_COUNT)
                err |= comedi_check_trigger_arg_min(&cmd->stop_arg, 1);
        else    /* cmd->stop_src == TRIG_NONE */
                err |= comedi_check_trigger_arg_is(&cmd->stop_arg, 0);

        if (err)
                return 3;

        /* step 4: fix up any arguments */

        if (cmd->convert_src == TRIG_TIMER) {
                /* round convert_arg to nearest microsecond */
                arg = cmd->convert_arg;
                arg = min(arg,
                          rounddown(UINT_MAX, (unsigned int)NSEC_PER_USEC));
                arg = NSEC_PER_USEC * DIV_ROUND_CLOSEST(arg, NSEC_PER_USEC);
                if (cmd->scan_begin_arg == TRIG_TIMER) {
                        /* limit convert_arg to keep scan_begin_arg in range */
                        limit = UINT_MAX / cmd->scan_end_arg;
                        limit = rounddown(limit, (unsigned int)NSEC_PER_SEC);
                        arg = min(arg, limit);
                }
                err |= comedi_check_trigger_arg_is(&cmd->convert_arg, arg);
        }

        if (cmd->scan_begin_src == TRIG_TIMER) {
                /* round scan_begin_arg to nearest microsecond */
                arg = cmd->scan_begin_arg;
                arg = min(arg,
                          rounddown(UINT_MAX, (unsigned int)NSEC_PER_USEC));
                arg = NSEC_PER_USEC * DIV_ROUND_CLOSEST(arg, NSEC_PER_USEC);
                if (cmd->convert_src == TRIG_TIMER) {
                        /* but ensure scan_begin_arg is large enough */
                        arg = max(arg, cmd->convert_arg * cmd->scan_end_arg);
                }
                err |= comedi_check_trigger_arg_is(&cmd->scan_begin_arg, arg);
        }

        if (err)
                return 4;

        return 0;
}

static int waveform_ai_cmd(struct comedi_device *dev,
                           struct comedi_subdevice *s)
{
        struct waveform_private *devpriv = dev->private;
        struct comedi_cmd *cmd = &s->async->cmd;
        unsigned int first_convert_time;
        u64 wf_current;

        if (cmd->flags & CMDF_PRIORITY) {
                dev_err(dev->class_dev,
                        "commands at RT priority not supported in this driver\n");
                return -1;
        }

        if (cmd->convert_src == TRIG_NOW)
                devpriv->ai_convert_period = 0;
        else            /* cmd->convert_src == TRIG_TIMER */
                devpriv->ai_convert_period = cmd->convert_arg / NSEC_PER_USEC;

        if (cmd->scan_begin_src == TRIG_FOLLOW) {
                devpriv->ai_scan_period = devpriv->ai_convert_period *
                                          cmd->scan_end_arg;
        } else {        /* cmd->scan_begin_src == TRIG_TIMER */
                devpriv->ai_scan_period = cmd->scan_begin_arg / NSEC_PER_USEC;
        }

        /*
         * Simulate first conversion to occur at convert period after
         * conversion timer starts.  If scan_begin_src is TRIG_FOLLOW, assume
         * the conversion timer starts immediately.  If scan_begin_src is
         * TRIG_TIMER, assume the conversion timer starts after the scan
         * period.
         */
        first_convert_time = devpriv->ai_convert_period;
        if (cmd->scan_begin_src == TRIG_TIMER)
                first_convert_time += devpriv->ai_scan_period;
        devpriv->ai_convert_time = ktime_to_us(ktime_get()) +
                                   first_convert_time;

        /* Determine time within waveform period at time of conversion. */
        wf_current = devpriv->ai_convert_time;
        devpriv->wf_current = do_div(wf_current, devpriv->wf_period);

        /*
         * Schedule timer to expire just after first conversion time.
         * Seem to need an extra jiffy here, otherwise timer expires slightly
         * early!
         */
        devpriv->ai_timer.expires =
                jiffies + usecs_to_jiffies(devpriv->ai_convert_period) + 1;
        add_timer(&devpriv->ai_timer);
        return 0;
}

static int waveform_ai_cancel(struct comedi_device *dev,
                              struct comedi_subdevice *s)
{
        struct waveform_private *devpriv = dev->private;

        if (in_softirq()) {
                /* Assume we were called from the timer routine itself. */
                del_timer(&devpriv->ai_timer);
        } else {
                del_timer_sync(&devpriv->ai_timer);
        }
        return 0;
}

static int waveform_ai_insn_read(struct comedi_device *dev,
                                 struct comedi_subdevice *s,
                                 struct comedi_insn *insn, unsigned int *data)
{
        struct waveform_private *devpriv = dev->private;
        int i, chan = CR_CHAN(insn->chanspec);

        for (i = 0; i < insn->n; i++)
                data[i] = devpriv->ao_loopbacks[chan];

        return insn->n;
}

/*
 * This is the background routine to handle AO commands, scheduled by
 * a timer mechanism.
 */
static void waveform_ao_timer(struct timer_list *t)
{
        struct waveform_private *devpriv = from_timer(devpriv, t, ao_timer);
        struct comedi_device *dev = devpriv->dev;
        struct comedi_subdevice *s = dev->write_subdev;
        struct comedi_async *async = s->async;
        struct comedi_cmd *cmd = &async->cmd;
        u64 now;
        u64 scans_since;
        unsigned int scans_avail = 0;

        /* determine number of scan periods since last time */
        now = ktime_to_us(ktime_get());
        scans_since = now - devpriv->ao_last_scan_time;
        do_div(scans_since, devpriv->ao_scan_period);
        if (scans_since) {
                unsigned int i;

                /* determine scans in buffer, limit to scans to do this time */
                scans_avail = comedi_nscans_left(s, 0);
                if (scans_avail > scans_since)
                        scans_avail = scans_since;
                if (scans_avail) {
                        /* skip all but the last scan to save processing time */
                        if (scans_avail > 1) {
                                unsigned int skip_bytes, nbytes;

                                skip_bytes =
                                comedi_samples_to_bytes(s, cmd->scan_end_arg *
                                                           (scans_avail - 1));
                                nbytes = comedi_buf_read_alloc(s, skip_bytes);
                                comedi_buf_read_free(s, nbytes);
                                comedi_inc_scan_progress(s, nbytes);
                                if (nbytes < skip_bytes) {
                                        /* unexpected underrun! (cancelled?) */
                                        async->events |= COMEDI_CB_OVERFLOW;
                                        goto underrun;
                                }
                        }
                        /* output the last scan */
                        for (i = 0; i < cmd->scan_end_arg; i++) {
                                unsigned int chan = CR_CHAN(cmd->chanlist[i]);
                                unsigned short *pd;

                                pd = &devpriv->ao_loopbacks[chan];

                                if (!comedi_buf_read_samples(s, pd, 1)) {
                                        /* unexpected underrun! (cancelled?) */
                                        async->events |= COMEDI_CB_OVERFLOW;
                                        goto underrun;
                                }
                        }
                        /* advance time of last scan */
                        devpriv->ao_last_scan_time +=
                                (u64)scans_avail * devpriv->ao_scan_period;
                }
        }
        if (cmd->stop_src == TRIG_COUNT && async->scans_done >= cmd->stop_arg) {
                async->events |= COMEDI_CB_EOA;
        } else if (scans_avail < scans_since) {
                async->events |= COMEDI_CB_OVERFLOW;
        } else {
                unsigned int time_inc = devpriv->ao_last_scan_time +
                                        devpriv->ao_scan_period - now;

                mod_timer(&devpriv->ao_timer,
                          jiffies + usecs_to_jiffies(time_inc));
        }

underrun:
        comedi_handle_events(dev, s);
}

static int waveform_ao_inttrig_start(struct comedi_device *dev,
                                     struct comedi_subdevice *s,
                                     unsigned int trig_num)
{
        struct waveform_private *devpriv = dev->private;
        struct comedi_async *async = s->async;
        struct comedi_cmd *cmd = &async->cmd;

        if (trig_num != cmd->start_arg)
                return -EINVAL;

        async->inttrig = NULL;

        devpriv->ao_last_scan_time = ktime_to_us(ktime_get());
        devpriv->ao_timer.expires =
                jiffies + usecs_to_jiffies(devpriv->ao_scan_period);
        add_timer(&devpriv->ao_timer);

        return 1;
}

static int waveform_ao_cmdtest(struct comedi_device *dev,
                               struct comedi_subdevice *s,
                               struct comedi_cmd *cmd)
{
        int err = 0;
        unsigned int arg;

        /* Step 1 : check if triggers are trivially valid */

        err |= comedi_check_trigger_src(&cmd->start_src, TRIG_INT);
        err |= comedi_check_trigger_src(&cmd->scan_begin_src, TRIG_TIMER);
        err |= comedi_check_trigger_src(&cmd->convert_src, TRIG_NOW);
        err |= comedi_check_trigger_src(&cmd->scan_end_src, TRIG_COUNT);
        err |= comedi_check_trigger_src(&cmd->stop_src, TRIG_COUNT | TRIG_NONE);

        if (err)
                return 1;

        /* Step 2a : make sure trigger sources are unique */

        err |= comedi_check_trigger_is_unique(cmd->stop_src);

        /* Step 2b : and mutually compatible */

        if (err)
                return 2;

        /* Step 3: check if arguments are trivially valid */

        err |= comedi_check_trigger_arg_min(&cmd->scan_begin_arg,
                                            NSEC_PER_USEC);
        err |= comedi_check_trigger_arg_is(&cmd->convert_arg, 0);
        err |= comedi_check_trigger_arg_min(&cmd->chanlist_len, 1);
        err |= comedi_check_trigger_arg_is(&cmd->scan_end_arg,
                                           cmd->chanlist_len);
        if (cmd->stop_src == TRIG_COUNT)
                err |= comedi_check_trigger_arg_min(&cmd->stop_arg, 1);
        else    /* cmd->stop_src == TRIG_NONE */
                err |= comedi_check_trigger_arg_is(&cmd->stop_arg, 0);

        if (err)
                return 3;

        /* step 4: fix up any arguments */

        /* round scan_begin_arg to nearest microsecond */
        arg = cmd->scan_begin_arg;
        arg = min(arg, rounddown(UINT_MAX, (unsigned int)NSEC_PER_USEC));
        arg = NSEC_PER_USEC * DIV_ROUND_CLOSEST(arg, NSEC_PER_USEC);
        err |= comedi_check_trigger_arg_is(&cmd->scan_begin_arg, arg);

        if (err)
                return 4;

        return 0;
}

static int waveform_ao_cmd(struct comedi_device *dev,
                           struct comedi_subdevice *s)
{
        struct waveform_private *devpriv = dev->private;
        struct comedi_cmd *cmd = &s->async->cmd;

        if (cmd->flags & CMDF_PRIORITY) {
                dev_err(dev->class_dev,
                        "commands at RT priority not supported in this driver\n");
                return -1;
        }

        devpriv->ao_scan_period = cmd->scan_begin_arg / NSEC_PER_USEC;
        s->async->inttrig = waveform_ao_inttrig_start;
        return 0;
}

static int waveform_ao_cancel(struct comedi_device *dev,
                              struct comedi_subdevice *s)
{
        struct waveform_private *devpriv = dev->private;

        s->async->inttrig = NULL;
        if (in_softirq()) {
                /* Assume we were called from the timer routine itself. */
                del_timer(&devpriv->ao_timer);
        } else {
                del_timer_sync(&devpriv->ao_timer);
        }
        return 0;
}

static int waveform_ao_insn_write(struct comedi_device *dev,
                                  struct comedi_subdevice *s,
                                  struct comedi_insn *insn, unsigned int *data)
{
        struct waveform_private *devpriv = dev->private;
        int i, chan = CR_CHAN(insn->chanspec);

        for (i = 0; i < insn->n; i++)
                devpriv->ao_loopbacks[chan] = data[i];

        return insn->n;
}

static int waveform_ai_insn_config(struct comedi_device *dev,
                                   struct comedi_subdevice *s,
                                   struct comedi_insn *insn,
                                   unsigned int *data)
{
        if (data[0] == INSN_CONFIG_GET_CMD_TIMING_CONSTRAINTS) {
                /*
                 * input:  data[1], data[2] : scan_begin_src, convert_src
                 * output: data[1], data[2] : scan_begin_min, convert_min
                 */
                if (data[1] == TRIG_FOLLOW) {
                        /* exactly TRIG_FOLLOW case */
                        data[1] = 0;
                        data[2] = NSEC_PER_USEC;
                } else {
                        data[1] = NSEC_PER_USEC;
                        if (data[2] & TRIG_TIMER)
                                data[2] = NSEC_PER_USEC;
                        else
                                data[2] = 0;
                }
                return 0;
        }

        return -EINVAL;
}

static int waveform_ao_insn_config(struct comedi_device *dev,
                                   struct comedi_subdevice *s,
                                   struct comedi_insn *insn,
                                   unsigned int *data)
{
        if (data[0] == INSN_CONFIG_GET_CMD_TIMING_CONSTRAINTS) {
                /* we don't care about actual channels */
                data[1] = NSEC_PER_USEC; /* scan_begin_min */
                data[2] = 0;             /* convert_min */
                return 0;
        }

        return -EINVAL;
}

static int waveform_common_attach(struct comedi_device *dev,
                                  int amplitude, int period)
{
        struct waveform_private *devpriv;
        struct comedi_subdevice *s;
        int i;
        int ret;

        devpriv = comedi_alloc_devpriv(dev, sizeof(*devpriv));
        if (!devpriv)
                return -ENOMEM;

        devpriv->wf_amplitude = amplitude;
        devpriv->wf_period = period;

        ret = comedi_alloc_subdevices(dev, 2);
        if (ret)
                return ret;

        s = &dev->subdevices[0];
        dev->read_subdev = s;
        /* analog input subdevice */
        s->type = COMEDI_SUBD_AI;
        s->subdev_flags = SDF_READABLE | SDF_GROUND | SDF_CMD_READ;
        s->n_chan = N_CHANS;
        s->maxdata = 0xffff;
        s->range_table = &waveform_ai_ranges;
        s->len_chanlist = s->n_chan * 2;
        s->insn_read = waveform_ai_insn_read;
        s->do_cmd = waveform_ai_cmd;
        s->do_cmdtest = waveform_ai_cmdtest;
        s->cancel = waveform_ai_cancel;
        s->insn_config = waveform_ai_insn_config;

        s = &dev->subdevices[1];
        dev->write_subdev = s;
        /* analog output subdevice (loopback) */
        s->type = COMEDI_SUBD_AO;
        s->subdev_flags = SDF_WRITABLE | SDF_GROUND | SDF_CMD_WRITE;
        s->n_chan = N_CHANS;
        s->maxdata = 0xffff;
        s->range_table = &waveform_ai_ranges;
        s->len_chanlist = s->n_chan;
        s->insn_write = waveform_ao_insn_write;
        s->insn_read = waveform_ai_insn_read;   /* do same as AI insn_read */
        s->do_cmd = waveform_ao_cmd;
        s->do_cmdtest = waveform_ao_cmdtest;
        s->cancel = waveform_ao_cancel;
        s->insn_config = waveform_ao_insn_config;

        /* Our default loopback value is just a 0V flatline */
        for (i = 0; i < s->n_chan; i++)
                devpriv->ao_loopbacks[i] = s->maxdata / 2;

        devpriv->dev = dev;
        timer_setup(&devpriv->ai_timer, waveform_ai_timer, 0);
        timer_setup(&devpriv->ao_timer, waveform_ao_timer, 0);

        dev_info(dev->class_dev,
                 "%s: %u microvolt, %u microsecond waveform attached\n",
                 dev->board_name,
                 devpriv->wf_amplitude, devpriv->wf_period);

        return 0;
}

static int waveform_attach(struct comedi_device *dev,
                           struct comedi_devconfig *it)
{
        int amplitude = it->options[0];
        int period = it->options[1];

        /* set default amplitude and period */
        if (amplitude <= 0)
                amplitude = 1000000;    /* 1 volt */
        if (period <= 0)
                period = 100000;        /* 0.1 sec */

        return waveform_common_attach(dev, amplitude, period);
}

static int waveform_auto_attach(struct comedi_device *dev,
                                unsigned long context_unused)
{
        int amplitude = set_amplitude;
        int period = set_period;

        /* set default amplitude and period */
        if (!amplitude)
                amplitude = 1000000;    /* 1 volt */
        if (!period)
                period = 100000;        /* 0.1 sec */

        return waveform_common_attach(dev, amplitude, period);
}

static void waveform_detach(struct comedi_device *dev)
{
        struct waveform_private *devpriv = dev->private;

        if (devpriv) {
                del_timer_sync(&devpriv->ai_timer);
                del_timer_sync(&devpriv->ao_timer);
        }
}

static struct comedi_driver waveform_driver = {
        .driver_name    = "comedi_test",
        .module         = THIS_MODULE,
        .attach         = waveform_attach,
        .auto_attach    = waveform_auto_attach,
        .detach         = waveform_detach,
};

/*
 * For auto-configuration, a device is created to stand in for a
 * real hardware device.
 */
static int __init comedi_test_init(void)
{
        int ret;

        ret = comedi_driver_register(&waveform_driver);
        if (ret) {
                pr_err("comedi_test: unable to register driver\n");
                return ret;
        }

        if (!config_mode) {
                ctcls = class_create(THIS_MODULE, CLASS_NAME);
                if (IS_ERR(ctcls)) {
                        pr_warn("comedi_test: unable to create class\n");
                        goto clean3;
                }

                ctdev = device_create(ctcls, NULL, MKDEV(0, 0), NULL, DEV_NAME);
                if (IS_ERR(ctdev)) {
                        pr_warn("comedi_test: unable to create device\n");
                        goto clean2;
                }

                ret = comedi_auto_config(ctdev, &waveform_driver, 0);
                if (ret) {
                        pr_warn("comedi_test: unable to auto-configure device\n");
                        goto clean;
                }
        }

        return 0;

clean:
        device_destroy(ctcls, MKDEV(0, 0));
clean2:
        class_destroy(ctcls);
        ctdev = NULL;
clean3:
        ctcls = NULL;

        return 0;
}
module_init(comedi_test_init);

static void __exit comedi_test_exit(void)
{
        if (ctdev)
                comedi_auto_unconfig(ctdev);

        if (ctcls) {
                device_destroy(ctcls, MKDEV(0, 0));
                class_destroy(ctcls);
        }

        comedi_driver_unregister(&waveform_driver);
}
module_exit(comedi_test_exit);

MODULE_AUTHOR("Comedi https://www.comedi.org");
MODULE_DESCRIPTION("Comedi low-level driver");
MODULE_LICENSE("GPL");