text: /*
   * A driver for the AverMedia MR 800 USB FM radio. This device plugs
   * into both the USB and an analog audio input, so this thing
   * only deals with initialization and frequency setting, the
   * audio data has to be handled by a sound driver.
   *
   * Copyright (c) 2008 Alexey Klimov <klimov.linux@gmail.com>
   *
   * This program is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License as published by
   * the Free Software Foundation; either version 2 of the License, or
   * (at your option) any later version.
   *
   * This program is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   * GNU General Public License for more details.
   *
   * You should have received a copy of the GNU General Public License
   * along with this program; if not, write to the Free Software
   * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
   */
  
  /*
   * Big thanks to authors and contributors of dsbr100.c and radio-si470x.c
   *
   * When work was looked pretty good, i discover this:
   * http://av-usbradio.sourceforge.net/index.php
   * http://sourceforge.net/projects/av-usbradio/
   * Latest release of theirs project was in 2005.
   * Probably, this driver could be improved through using their
   * achievements (specifications given).
   * Also, Faidon Liambotis <paravoid@debian.org> wrote nice driver for this radio
   * in 2007. He allowed to use his driver to improve current mr800 radio driver.
   * http://kerneltrap.org/mailarchive/linux-usb-devel/2007/10/11/342492
   *
   * Version 0.01:	First working version.
   * 			It's required to blacklist AverMedia USB Radio
   * 			in usbhid/hid-quirks.c
   * Version 0.10:	A lot of cleanups and fixes: unpluging the device,
   * 			few mutex locks were added, codinstyle issues, etc.
   * 			Added stereo support. Thanks to
   * 			Douglas Schilling Landgraf <dougsland@gmail.com> and
   * 			David Ellingsworth <david@identd.dyndns.org>
   * 			for discussion, help and support.
   * Version 0.11:	Converted to v4l2_device.
   *
   * Many things to do:
   * 	- Correct power management of device (suspend & resume)
   * 	- Add code for scanning and smooth tuning
   * 	- Add code for sensitivity value
   * 	- Correct mistakes
   * 	- In Japan another FREQ_MIN and FREQ_MAX
   */
  
  /* kernel includes */
  #include <linux/kernel.h>
  #include <linux/module.h>
  #include <linux/init.h>
  #include <linux/slab.h>
  #include <linux/smp_lock.h>
  #include <linux/input.h>
  #include <linux/videodev2.h>
  #include <media/v4l2-device.h>
  #include <media/v4l2-ioctl.h>
  #include <linux/usb.h>
  #include <linux/version.h>	/* for KERNEL_VERSION MACRO */
  #include <linux/mutex.h>
  
  /* driver and module definitions */
  #define DRIVER_AUTHOR "Alexey Klimov <klimov.linux@gmail.com>"
  #define DRIVER_DESC "AverMedia MR 800 USB FM radio driver"
  #define DRIVER_VERSION "0.11"
  #define RADIO_VERSION KERNEL_VERSION(0, 1, 1)
  
  MODULE_AUTHOR(DRIVER_AUTHOR);
  MODULE_DESCRIPTION(DRIVER_DESC);
  MODULE_LICENSE("GPL");
  
  #define USB_AMRADIO_VENDOR 0x07ca
  #define USB_AMRADIO_PRODUCT 0xb800
  
  /* dev_warn macro with driver name */
  #define MR800_DRIVER_NAME "radio-mr800"
  #define amradio_dev_warn(dev, fmt, arg...)				\
  		dev_warn(dev, MR800_DRIVER_NAME " - " fmt, ##arg)
  
  #define amradio_dev_err(dev, fmt, arg...) \
  		dev_err(dev, MR800_DRIVER_NAME " - " fmt, ##arg)
  
  /* Probably USB_TIMEOUT should be modified in module parameter */
  #define BUFFER_LENGTH 8
  #define USB_TIMEOUT 500
  
  /* Frequency limits in MHz -- these are European values.  For Japanese
  devices, that would be 76 and 91.  */
  #define FREQ_MIN  87.5
  #define FREQ_MAX 108.0
  #define FREQ_MUL 16000
  
  /*
   * Commands that device should understand
   * List isnt full and will be updated with implementation of new functions
   */
  #define AMRADIO_SET_FREQ	0xa4
  #define AMRADIO_SET_MUTE	0xab
  #define AMRADIO_SET_MONO	0xae
  
  /* Comfortable defines for amradio_set_mute */
  #define AMRADIO_START		0x00
  #define AMRADIO_STOP		0x01
  
  /* Comfortable defines for amradio_set_stereo */
  #define WANT_STEREO		0x00
  #define WANT_MONO		0x01
  
  /* module parameter */
  static int radio_nr = -1;
  module_param(radio_nr, int, 0);
  MODULE_PARM_DESC(radio_nr, "Radio Nr");
  
  static int usb_amradio_probe(struct usb_interface *intf,
  			     const struct usb_device_id *id);
  static void usb_amradio_disconnect(struct usb_interface *intf);
  static int usb_amradio_open(struct file *file);
  static int usb_amradio_close(struct file *file);
  static int usb_amradio_suspend(struct usb_interface *intf,
  				pm_message_t message);
  static int usb_amradio_resume(struct usb_interface *intf);
  
  /* Data for one (physical) device */
  struct amradio_device {
  	/* reference to USB and video device */
  	struct usb_device *usbdev;
  	struct usb_interface *intf;
  	struct video_device videodev;
  	struct v4l2_device v4l2_dev;
  
  	unsigned char *buffer;
  	struct mutex lock;	/* buffer locking */
  	int curfreq;
  	int stereo;
  	int muted;
  	int initialized;
  };
  
  static inline struct amradio_device *to_amradio_dev(struct v4l2_device *v4l2_dev)
  {
  	return container_of(v4l2_dev, struct amradio_device, v4l2_dev);
  }
  
  /* USB Device ID List */
  static struct usb_device_id usb_amradio_device_table[] = {
  	{USB_DEVICE_AND_INTERFACE_INFO(USB_AMRADIO_VENDOR, USB_AMRADIO_PRODUCT,
  							USB_CLASS_HID, 0, 0) },
  	{ }						/* Terminating entry */
  };
  
  MODULE_DEVICE_TABLE(usb, usb_amradio_device_table);
  
  /* USB subsystem interface */
  static struct usb_driver usb_amradio_driver = {
  	.name			= MR800_DRIVER_NAME,
  	.probe			= usb_amradio_probe,
  	.disconnect		= usb_amradio_disconnect,
  	.suspend		= usb_amradio_suspend,
  	.resume			= usb_amradio_resume,
  	.reset_resume		= usb_amradio_resume,
  	.id_table		= usb_amradio_device_table,
  	.supports_autosuspend	= 1,
  };
  
  /* switch on/off the radio. Send 8 bytes to device */
  static int amradio_set_mute(struct amradio_device *radio, char argument)
  {
  	int retval;
  	int size;
  
  	BUG_ON(!mutex_is_locked(&radio->lock));
  
  	radio->buffer[0] = 0x00;
  	radio->buffer[1] = 0x55;
  	radio->buffer[2] = 0xaa;
  	radio->buffer[3] = 0x00;
  	radio->buffer[4] = AMRADIO_SET_MUTE;
  	radio->buffer[5] = argument;
  	radio->buffer[6] = 0x00;
  	radio->buffer[7] = 0x00;
  
  	retval = usb_bulk_msg(radio->usbdev, usb_sndintpipe(radio->usbdev, 2),
  		(void *) (radio->buffer), BUFFER_LENGTH, &size, USB_TIMEOUT);
  
  	if (retval < 0 || size != BUFFER_LENGTH) {
  		amradio_dev_warn(&radio->videodev.dev, "set mute failed\n");
  		return retval;
  	}
  
  	radio->muted = argument;
  
  	return retval;
  }
  
  /* set a frequency, freq is defined by v4l's TUNER_LOW, i.e. 1/16th kHz */
  static int amradio_setfreq(struct amradio_device *radio, int freq)
  {
  	int retval;
  	int size;
  	unsigned short freq_send = 0x10 + (freq >> 3) / 25;
  
  	BUG_ON(!mutex_is_locked(&radio->lock));
  
  	radio->buffer[0] = 0x00;
  	radio->buffer[1] = 0x55;
  	radio->buffer[2] = 0xaa;
  	radio->buffer[3] = 0x03;
  	radio->buffer[4] = AMRADIO_SET_FREQ;
  	radio->buffer[5] = 0x00;
  	radio->buffer[6] = 0x00;
  	radio->buffer[7] = 0x08;
  
  	retval = usb_bulk_msg(radio->usbdev, usb_sndintpipe(radio->usbdev, 2),
  		(void *) (radio->buffer), BUFFER_LENGTH, &size, USB_TIMEOUT);
  
  	if (retval < 0 || size != BUFFER_LENGTH)
  		goto out_err;
  
  	/* frequency is calculated from freq_send and placed in first 2 bytes */
  	radio->buffer[0] = (freq_send >> 8) & 0xff;
  	radio->buffer[1] = freq_send & 0xff;
  	radio->buffer[2] = 0x01;
  	radio->buffer[3] = 0x00;
  	radio->buffer[4] = 0x00;
  	/* 5 and 6 bytes of buffer already = 0x00 */
  	radio->buffer[7] = 0x00;
  
  	retval = usb_bulk_msg(radio->usbdev, usb_sndintpipe(radio->usbdev, 2),
  		(void *) (radio->buffer), BUFFER_LENGTH, &size, USB_TIMEOUT);
  
  	if (retval < 0 || size != BUFFER_LENGTH)
  		goto out_err;
  
  	radio->curfreq = freq;
  	goto out;
  
  out_err:
  	amradio_dev_warn(&radio->videodev.dev, "set frequency failed\n");
  out:
  	return retval;
  }
  
  static int amradio_set_stereo(struct amradio_device *radio, char argument)
  {
  	int retval;
  	int size;
  
  	BUG_ON(!mutex_is_locked(&radio->lock));
  
  	radio->buffer[0] = 0x00;
  	radio->buffer[1] = 0x55;
  	radio->buffer[2] = 0xaa;
  	radio->buffer[3] = 0x00;
  	radio->buffer[4] = AMRADIO_SET_MONO;
  	radio->buffer[5] = argument;
  	radio->buffer[6] = 0x00;
  	radio->buffer[7] = 0x00;
  
  	retval = usb_bulk_msg(radio->usbdev, usb_sndintpipe(radio->usbdev, 2),
  		(void *) (radio->buffer), BUFFER_LENGTH, &size, USB_TIMEOUT);
  
  	if (retval < 0 || size != BUFFER_LENGTH) {
  		amradio_dev_warn(&radio->videodev.dev, "set stereo failed\n");
  		return retval;
  	}
  
  	if (argument == WANT_STEREO)
  		radio->stereo = 1;
  	else
  		radio->stereo = 0;
  
  	return retval;
  }
  
  /* Handle unplugging the device.
   * We call video_unregister_device in any case.
   * The last function called in this procedure is
   * usb_amradio_device_release.
   */
  static void usb_amradio_disconnect(struct usb_interface *intf)
  {
  	struct amradio_device *radio = to_amradio_dev(usb_get_intfdata(intf));
  
  	mutex_lock(&radio->lock);
  	radio->usbdev = NULL;
  	mutex_unlock(&radio->lock);
  
  	v4l2_device_disconnect(&radio->v4l2_dev);
  	video_unregister_device(&radio->videodev);
  }
  
  /* vidioc_querycap - query device capabilities */
  static int vidioc_querycap(struct file *file, void *priv,
  					struct v4l2_capability *v)
  {
  	struct amradio_device *radio = file->private_data;
  
  	strlcpy(v->driver, "radio-mr800", sizeof(v->driver));
  	strlcpy(v->card, "AverMedia MR 800 USB FM Radio", sizeof(v->card));
  	usb_make_path(radio->usbdev, v->bus_info, sizeof(v->bus_info));
  	v->version = RADIO_VERSION;
  	v->capabilities = V4L2_CAP_TUNER;
  	return 0;
  }
  
  /* vidioc_g_tuner - get tuner attributes */
  static int vidioc_g_tuner(struct file *file, void *priv,
  				struct v4l2_tuner *v)
  {
  	struct amradio_device *radio = file->private_data;
  	int retval;
  
  	if (v->index > 0)
  		return -EINVAL;
  
  /* TODO: Add function which look is signal stereo or not
   * 	amradio_getstat(radio);
   */
  
  /* we call amradio_set_stereo to set radio->stereo
   * Honestly, amradio_getstat should cover this in future and
   * amradio_set_stereo shouldn't be here
   */
  	retval = amradio_set_stereo(radio, WANT_STEREO);
  
  	strcpy(v->name, "FM");
  	v->type = V4L2_TUNER_RADIO;
  	v->rangelow = FREQ_MIN * FREQ_MUL;
  	v->rangehigh = FREQ_MAX * FREQ_MUL;
  	v->rxsubchans = V4L2_TUNER_SUB_MONO | V4L2_TUNER_SUB_STEREO;
  	v->capability = V4L2_TUNER_CAP_LOW;
  	if (radio->stereo)
  		v->audmode = V4L2_TUNER_MODE_STEREO;
  	else
  		v->audmode = V4L2_TUNER_MODE_MONO;
  	v->signal = 0xffff;     /* Can't get the signal strength, sad.. */
  	v->afc = 0; /* Don't know what is this */
  
  	return retval;
  }
  
  /* vidioc_s_tuner - set tuner attributes */
  static int vidioc_s_tuner(struct file *file, void *priv,
  				struct v4l2_tuner *v)
  {
  	struct amradio_device *radio = file->private_data;
  	int retval = -EINVAL;
  
  	if (v->index > 0)
  		return -EINVAL;
  
  	/* mono/stereo selector */
  	switch (v->audmode) {
  	case V4L2_TUNER_MODE_MONO:
  		retval = amradio_set_stereo(radio, WANT_MONO);
  		break;
  	case V4L2_TUNER_MODE_STEREO:
  		retval = amradio_set_stereo(radio, WANT_STEREO);
  		break;
  	}
  
  	return retval;
  }
  
  /* vidioc_s_frequency - set tuner radio frequency */
  static int vidioc_s_frequency(struct file *file, void *priv,
  				struct v4l2_frequency *f)
  {
  	struct amradio_device *radio = file->private_data;
  
  	if (f->tuner != 0 || f->type != V4L2_TUNER_RADIO)
  		return -EINVAL;
  	return amradio_setfreq(radio, f->frequency);
  }
  
  /* vidioc_g_frequency - get tuner radio frequency */
  static int vidioc_g_frequency(struct file *file, void *priv,
  				struct v4l2_frequency *f)
  {
  	struct amradio_device *radio = file->private_data;
  
  	if (f->tuner != 0)
  		return -EINVAL;
  	f->type = V4L2_TUNER_RADIO;
  	f->frequency = radio->curfreq;
  
  	return 0;
  }
  
  /* vidioc_queryctrl - enumerate control items */
  static int vidioc_queryctrl(struct file *file, void *priv,
  				struct v4l2_queryctrl *qc)
  {
  	switch (qc->id) {
  	case V4L2_CID_AUDIO_MUTE:
  		return v4l2_ctrl_query_fill(qc, 0, 1, 1, 1);
  	}
  
  	return -EINVAL;
  }
  
  /* vidioc_g_ctrl - get the value of a control */
  static int vidioc_g_ctrl(struct file *file, void *priv,
  				struct v4l2_control *ctrl)
  {
  	struct amradio_device *radio = file->private_data;
  
  	switch (ctrl->id) {
  	case V4L2_CID_AUDIO_MUTE:
  		ctrl->value = radio->muted;
  		return 0;
  	}
  
  	return -EINVAL;
  }
  
  /* vidioc_s_ctrl - set the value of a control */
  static int vidioc_s_ctrl(struct file *file, void *priv,
  				struct v4l2_control *ctrl)
  {
  	struct amradio_device *radio = file->private_data;
  	int retval = -EINVAL;
  
  	switch (ctrl->id) {
  	case V4L2_CID_AUDIO_MUTE:
  		if (ctrl->value)
  			retval = amradio_set_mute(radio, AMRADIO_STOP);
  		else
  			retval = amradio_set_mute(radio, AMRADIO_START);
  
  		break;
  	}
  
  	return retval;
  }
  
  /* vidioc_g_audio - get audio attributes */
  static int vidioc_g_audio(struct file *file, void *priv,
  				struct v4l2_audio *a)
  {
  	if (a->index > 1)
  		return -EINVAL;
  
  	strcpy(a->name, "Radio");
  	a->capability = V4L2_AUDCAP_STEREO;
  	return 0;
  }
  
  /* vidioc_s_audio - set audio attributes  */
  static int vidioc_s_audio(struct file *file, void *priv,
  					struct v4l2_audio *a)
  {
  	if (a->index != 0)
  		return -EINVAL;
  	return 0;
  }
  
  /* vidioc_g_input - get input */
  static int vidioc_g_input(struct file *filp, void *priv, unsigned int *i)
  {
  	*i = 0;
  	return 0;
  }
  
  /* vidioc_s_input - set input */
  static int vidioc_s_input(struct file *filp, void *priv, unsigned int i)
  {
  	if (i != 0)
  		return -EINVAL;
  	return 0;
  }
  
  static int usb_amradio_init(struct amradio_device *radio)
  {
  	int retval;
  
  	retval = amradio_set_mute(radio, AMRADIO_STOP);
  	if (retval)
  		goto out_err;
  
  	retval = amradio_set_stereo(radio, WANT_STEREO);
  	if (retval)
  		goto out_err;
  
  	radio->initialized = 1;
  	goto out;
  
  out_err:
  	amradio_dev_err(&radio->videodev.dev, "initialization failed\n");
  out:
  	return retval;
  }
  
  /* open device - amradio_start() and amradio_setfreq() */
  static int usb_amradio_open(struct file *file)
  {
  	struct amradio_device *radio = video_drvdata(file);
  	int retval = 0;
  
  	mutex_lock(&radio->lock);
  
  	if (!radio->usbdev) {
  		retval = -EIO;
  		goto unlock;
  	}
  
  	file->private_data = radio;
  	retval = usb_autopm_get_interface(radio->intf);
  	if (retval)
  		goto unlock;
  
  	if (unlikely(!radio->initialized)) {
  		retval = usb_amradio_init(radio);
  		if (retval)
  			usb_autopm_put_interface(radio->intf);
  	}
  
  unlock:
  	mutex_unlock(&radio->lock);
  	return retval;
  }
  
  /*close device */
  static int usb_amradio_close(struct file *file)
  {
  	struct amradio_device *radio = file->private_data;
  	int retval = 0;
  
  	mutex_lock(&radio->lock);
  
  	if (!radio->usbdev)
  		retval = -EIO;
  	else
  		usb_autopm_put_interface(radio->intf);
  
  	mutex_unlock(&radio->lock);
  	return retval;
  }
  
  static long usb_amradio_ioctl(struct file *file, unsigned int cmd,
  				unsigned long arg)
  {
  	struct amradio_device *radio = file->private_data;
  	long retval = 0;
  
  	mutex_lock(&radio->lock);
  
  	if (!radio->usbdev) {
  		retval = -EIO;
  		goto unlock;
  	}
  
  	retval = video_ioctl2(file, cmd, arg);
  
  unlock:
  	mutex_unlock(&radio->lock);
  	return retval;
  }
  
  /* Suspend device - stop device. Need to be checked and fixed */
  static int usb_amradio_suspend(struct usb_interface *intf, pm_message_t message)
  {
  	struct amradio_device *radio = to_amradio_dev(usb_get_intfdata(intf));
  
  	mutex_lock(&radio->lock);
  
  	if (!radio->muted && radio->initialized) {
  		amradio_set_mute(radio, AMRADIO_STOP);
  		radio->muted = 0;
  	}
  
  	dev_info(&intf->dev, "going into suspend..\n");
  
  	mutex_unlock(&radio->lock);
  	return 0;
  }
  
  /* Resume device - start device. Need to be checked and fixed */
  static int usb_amradio_resume(struct usb_interface *intf)
  {
  	struct amradio_device *radio = to_amradio_dev(usb_get_intfdata(intf));
  
  	mutex_lock(&radio->lock);
  
  	if (unlikely(!radio->initialized))
  		goto unlock;
  
  	if (radio->stereo)
  		amradio_set_stereo(radio, WANT_STEREO);
  	else
  		amradio_set_stereo(radio, WANT_MONO);
  
  	amradio_setfreq(radio, radio->curfreq);
  
  	if (!radio->muted)
  		amradio_set_mute(radio, AMRADIO_START);
  
  unlock:
  	dev_info(&intf->dev, "coming out of suspend..\n");
  
  	mutex_unlock(&radio->lock);
  	return 0;
  }
  
  /* File system interface */
  static const struct v4l2_file_operations usb_amradio_fops = {
  	.owner		= THIS_MODULE,
  	.open		= usb_amradio_open,
  	.release	= usb_amradio_close,
  	.ioctl		= usb_amradio_ioctl,
  };
  
  static const struct v4l2_ioctl_ops usb_amradio_ioctl_ops = {
  	.vidioc_querycap    = vidioc_querycap,
  	.vidioc_g_tuner     = vidioc_g_tuner,
  	.vidioc_s_tuner     = vidioc_s_tuner,
  	.vidioc_g_frequency = vidioc_g_frequency,
  	.vidioc_s_frequency = vidioc_s_frequency,
  	.vidioc_queryctrl   = vidioc_queryctrl,
  	.vidioc_g_ctrl      = vidioc_g_ctrl,
  	.vidioc_s_ctrl      = vidioc_s_ctrl,
  	.vidioc_g_audio     = vidioc_g_audio,
  	.vidioc_s_audio     = vidioc_s_audio,
  	.vidioc_g_input     = vidioc_g_input,
  	.vidioc_s_input     = vidioc_s_input,
  };
  
  static void usb_amradio_video_device_release(struct video_device *videodev)
  {
  	struct amradio_device *radio = video_get_drvdata(videodev);
  
  	/* free rest memory */
  	kfree(radio->buffer);
  	kfree(radio);
  }
  
  /* check if the device is present and register with v4l and usb if it is */
  static int usb_amradio_probe(struct usb_interface *intf,
  				const struct usb_device_id *id)
  {
  	struct amradio_device *radio;
  	int retval = 0;
  
  	radio = kzalloc(sizeof(struct amradio_device), GFP_KERNEL);
  
  	if (!radio) {
  		dev_err(&intf->dev, "kmalloc for amradio_device failed\n");
  		retval = -ENOMEM;
  		goto err;
  	}
  
  	radio->buffer = kmalloc(BUFFER_LENGTH, GFP_KERNEL);
  
  	if (!radio->buffer) {
  		dev_err(&intf->dev, "kmalloc for radio->buffer failed\n");
  		retval = -ENOMEM;
  		goto err_nobuf;
  	}
  
  	retval = v4l2_device_register(&intf->dev, &radio->v4l2_dev);
  	if (retval < 0) {
  		dev_err(&intf->dev, "couldn't register v4l2_device\n");
  		goto err_v4l2;
  	}
  
  	strlcpy(radio->videodev.name, radio->v4l2_dev.name,
  		sizeof(radio->videodev.name));
  	radio->videodev.v4l2_dev = &radio->v4l2_dev;
  	radio->videodev.fops = &usb_amradio_fops;
  	radio->videodev.ioctl_ops = &usb_amradio_ioctl_ops;
  	radio->videodev.release = usb_amradio_video_device_release;
  
  	radio->usbdev = interface_to_usbdev(intf);
  	radio->intf = intf;
  	radio->curfreq = 95.16 * FREQ_MUL;
  
  	mutex_init(&radio->lock);
  
  	video_set_drvdata(&radio->videodev, radio);
  
  	retval = video_register_device(&radio->videodev, VFL_TYPE_RADIO,
  					radio_nr);
  	if (retval < 0) {
  		dev_err(&intf->dev, "could not register video device\n");
  		goto err_vdev;
  	}
  
  	return 0;
  
  err_vdev:
  	v4l2_device_unregister(&radio->v4l2_dev);
  err_v4l2:
  	kfree(radio->buffer);
  err_nobuf:
  	kfree(radio);
  err:
  	return retval;
  }
  
  static int __init amradio_init(void)
  {
  	int retval = usb_register(&usb_amradio_driver);
  
  	pr_info(KBUILD_MODNAME
  		": version " DRIVER_VERSION " " DRIVER_DESC "\n");
  
  	if (retval)
  		pr_err(KBUILD_MODNAME
  			": usb_register failed. Error number %d\n", retval);
  
  	return retval;
  }
  
  static void __exit amradio_exit(void)
  {
  	usb_deregister(&usb_amradio_driver);
  }
  
  module_init(amradio_init);
  module_exit(amradio_exit);
  
  