drivers/media/radio/radio-ma901.c - arm/linux-arm64-legacy - Git at Google

 /*
  * Driver for the MasterKit MA901 USB FM radio. This device plugs
  * into the USB port and an analog audio input or headphones, so this thing
  * only deals with initialization, frequency setting, volume.
  *
  * Copyright (c) 2012 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
  */

 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/init.h>
 #include <linux/slab.h>
 #include <linux/input.h>
 #include <linux/videodev2.h>
 #include <media/v4l2-device.h>
 #include <media/v4l2-ioctl.h>
 #include <media/v4l2-ctrls.h>
 #include <media/v4l2-event.h>
 #include <linux/usb.h>
 #include <linux/mutex.h>

 #define DRIVER_AUTHOR "Alexey Klimov <klimov.linux@gmail.com>"
 #define DRIVER_DESC "Masterkit MA901 USB FM radio driver"
 #define DRIVER_VERSION "0.0.1"

 MODULE_AUTHOR(DRIVER_AUTHOR);
 MODULE_DESCRIPTION(DRIVER_DESC);
 MODULE_LICENSE("GPL");
 MODULE_VERSION(DRIVER_VERSION);

 #define USB_MA901_VENDOR  0x16c0
 #define USB_MA901_PRODUCT 0x05df

 /* dev_warn macro with driver name */
 #define MA901_DRIVER_NAME "radio-ma901"
 #define ma901radio_dev_warn(dev, fmt, arg...)				\
 		dev_warn(dev, MA901_DRIVER_NAME " - " fmt, ##arg)

 #define ma901radio_dev_err(dev, fmt, arg...) \
 		dev_err(dev, MA901_DRIVER_NAME " - " fmt, ##arg)

 /* Probably USB_TIMEOUT should be modified in module parameter */
 #define BUFFER_LENGTH 8
 #define USB_TIMEOUT 500

 #define FREQ_MIN  87.5
 #define FREQ_MAX 108.0
 #define FREQ_MUL 16000

 #define MA901_VOLUME_MAX 16
 #define MA901_VOLUME_MIN 0

 /* Commands that device should understand
  * List isn't full and will be updated with implementation of new functions
  */
 #define MA901_RADIO_SET_FREQ		0x03
 #define MA901_RADIO_SET_VOLUME		0x04
 #define MA901_RADIO_SET_MONO_STEREO	0x05

 /* Comfortable defines for ma901radio_set_stereo */
 #define MA901_WANT_STEREO		0x50
 #define MA901_WANT_MONO			0xd0

 /* module parameter */
 static int radio_nr = -1;
 module_param(radio_nr, int, 0);
 MODULE_PARM_DESC(radio_nr, "Radio file number");

 /* Data for one (physical) device */
 struct ma901radio_device {
 	/* reference to USB and video device */
 	struct usb_device *usbdev;
 	struct usb_interface *intf;
 	struct video_device vdev;
 	struct v4l2_device v4l2_dev;
 	struct v4l2_ctrl_handler hdl;

 	u8 *buffer;
 	struct mutex lock;	/* buffer locking */
 	int curfreq;
 	u16 volume;
 	int stereo;
 	bool muted;
 };

 static inline struct ma901radio_device *to_ma901radio_dev(struct v4l2_device *v4l2_dev)
 {
 	return container_of(v4l2_dev, struct ma901radio_device, v4l2_dev);
 }

 /* set a frequency, freq is defined by v4l's TUNER_LOW, i.e. 1/16th kHz */
 static int ma901radio_set_freq(struct ma901radio_device *radio, int freq)
 {
 	unsigned int freq_send = 0x300 + (freq >> 5) / 25;
 	int retval;

 	radio->buffer[0] = 0x0a;
 	radio->buffer[1] = MA901_RADIO_SET_FREQ;
 	radio->buffer[2] = ((freq_send >> 8) & 0xff) + 0x80;
 	radio->buffer[3] = freq_send & 0xff;
 	radio->buffer[4] = 0x00;
 	radio->buffer[5] = 0x00;
 	radio->buffer[6] = 0x00;
 	radio->buffer[7] = 0x00;

 	retval = usb_control_msg(radio->usbdev, usb_sndctrlpipe(radio->usbdev, 0),
 				9, 0x21, 0x0300, 0,
 				radio->buffer, BUFFER_LENGTH, USB_TIMEOUT);
 	if (retval < 0)
 		return retval;

 	radio->curfreq = freq;
 	return 0;
 }

 static int ma901radio_set_volume(struct ma901radio_device *radio, u16 vol_to_set)
 {
 	int retval;

 	radio->buffer[0] = 0x0a;
 	radio->buffer[1] = MA901_RADIO_SET_VOLUME;
 	radio->buffer[2] = 0xc2;
 	radio->buffer[3] = vol_to_set + 0x20;
 	radio->buffer[4] = 0x00;
 	radio->buffer[5] = 0x00;
 	radio->buffer[6] = 0x00;
 	radio->buffer[7] = 0x00;

 	retval = usb_control_msg(radio->usbdev, usb_sndctrlpipe(radio->usbdev, 0),
 				9, 0x21, 0x0300, 0,
 				radio->buffer, BUFFER_LENGTH, USB_TIMEOUT);
 	if (retval < 0)
 		return retval;

 	radio->volume = vol_to_set;
 	return retval;
 }

 static int ma901_set_stereo(struct ma901radio_device *radio, u8 stereo)
 {
 	int retval;

 	radio->buffer[0] = 0x0a;
 	radio->buffer[1] = MA901_RADIO_SET_MONO_STEREO;
 	radio->buffer[2] = stereo;
 	radio->buffer[3] = 0x00;
 	radio->buffer[4] = 0x00;
 	radio->buffer[5] = 0x00;
 	radio->buffer[6] = 0x00;
 	radio->buffer[7] = 0x00;

 	retval = usb_control_msg(radio->usbdev, usb_sndctrlpipe(radio->usbdev, 0),
 				9, 0x21, 0x0300, 0,
 				radio->buffer, BUFFER_LENGTH, USB_TIMEOUT);

 	if (retval < 0)
 		return retval;

 	if (stereo == MA901_WANT_STEREO)
 		radio->stereo = V4L2_TUNER_MODE_STEREO;
 	else
 		radio->stereo = V4L2_TUNER_MODE_MONO;

 	return retval;
 }

 /* Handle unplugging the device.
  * We call video_unregister_device in any case.
  * The last function called in this procedure is
  * usb_ma901radio_device_release.
  */
 static void usb_ma901radio_disconnect(struct usb_interface *intf)
 {
 	struct ma901radio_device *radio = to_ma901radio_dev(usb_get_intfdata(intf));

 	mutex_lock(&radio->lock);
 	video_unregister_device(&radio->vdev);
 	usb_set_intfdata(intf, NULL);
 	v4l2_device_disconnect(&radio->v4l2_dev);
 	mutex_unlock(&radio->lock);
 	v4l2_device_put(&radio->v4l2_dev);
 }

 /* vidioc_querycap - query device capabilities */
 static int vidioc_querycap(struct file *file, void *priv,
 					struct v4l2_capability *v)
 {
 	struct ma901radio_device *radio = video_drvdata(file);

 	strlcpy(v->driver, "radio-ma901", sizeof(v->driver));
 	strlcpy(v->card, "Masterkit MA901 USB FM Radio", sizeof(v->card));
 	usb_make_path(radio->usbdev, v->bus_info, sizeof(v->bus_info));
 	v->device_caps = V4L2_CAP_RADIO | V4L2_CAP_TUNER;
 	v->capabilities = v->device_caps | V4L2_CAP_DEVICE_CAPS;
 	return 0;
 }

 /* vidioc_g_tuner - get tuner attributes */
 static int vidioc_g_tuner(struct file *file, void *priv,
 				struct v4l2_tuner *v)
 {
 	struct ma901radio_device *radio = video_drvdata(file);

 	if (v->index > 0)
 		return -EINVAL;

 	v->signal = 0;

 	/* TODO: the same words like in _probe() goes here.
 	 * When receiving of stats will be implemented then we can call
 	 * ma901radio_get_stat().
 	 * retval = ma901radio_get_stat(radio, &is_stereo, &v->signal);
 	 */

 	strcpy(v->name, "FM");
 	v->type = V4L2_TUNER_RADIO;
 	v->rangelow = FREQ_MIN * FREQ_MUL;
 	v->rangehigh = FREQ_MAX * FREQ_MUL;
 	v->capability = V4L2_TUNER_CAP_LOW | V4L2_TUNER_CAP_STEREO;
 	/* v->rxsubchans = is_stereo ? V4L2_TUNER_SUB_STEREO : V4L2_TUNER_SUB_MONO; */
 	v->audmode = radio->stereo ?
 		V4L2_TUNER_MODE_STEREO : V4L2_TUNER_MODE_MONO;
 	return 0;
 }

 /* vidioc_s_tuner - set tuner attributes */
 static int vidioc_s_tuner(struct file *file, void *priv,
 				const struct v4l2_tuner *v)
 {
 	struct ma901radio_device *radio = video_drvdata(file);

 	if (v->index > 0)
 		return -EINVAL;

 	/* mono/stereo selector */
 	switch (v->audmode) {
 	case V4L2_TUNER_MODE_MONO:
 		return ma901_set_stereo(radio, MA901_WANT_MONO);
 	default:
 		return ma901_set_stereo(radio, MA901_WANT_STEREO);
 	}
 }

 /* vidioc_s_frequency - set tuner radio frequency */
 static int vidioc_s_frequency(struct file *file, void *priv,
 				const struct v4l2_frequency *f)
 {
 	struct ma901radio_device *radio = video_drvdata(file);

 	if (f->tuner != 0)
 		return -EINVAL;

 	return ma901radio_set_freq(radio, clamp_t(unsigned, f->frequency,
 				FREQ_MIN * FREQ_MUL, FREQ_MAX * FREQ_MUL));
 }

 /* vidioc_g_frequency - get tuner radio frequency */
 static int vidioc_g_frequency(struct file *file, void *priv,
 				struct v4l2_frequency *f)
 {
 	struct ma901radio_device *radio = video_drvdata(file);

 	if (f->tuner != 0)
 		return -EINVAL;
 	f->frequency = radio->curfreq;

 	return 0;
 }

 static int usb_ma901radio_s_ctrl(struct v4l2_ctrl *ctrl)
 {
 	struct ma901radio_device *radio =
 		container_of(ctrl->handler, struct ma901radio_device, hdl);

 	switch (ctrl->id) {
 	case V4L2_CID_AUDIO_VOLUME:     /* set volume */
 		return ma901radio_set_volume(radio, (u16)ctrl->val);
 	}

 	return -EINVAL;
 }

 /* TODO: Should we really need to implement suspend and resume functions?
  * Radio has it's own memory and will continue playing if power is present
  * on usb port and on resume it will start to play again based on freq, volume
  * values in device memory.
  */
 static int usb_ma901radio_suspend(struct usb_interface *intf, pm_message_t message)
 {
 	return 0;
 }

 static int usb_ma901radio_resume(struct usb_interface *intf)
 {
 	return 0;
 }

 static const struct v4l2_ctrl_ops usb_ma901radio_ctrl_ops = {
 	.s_ctrl = usb_ma901radio_s_ctrl,
 };

 /* File system interface */
 static const struct v4l2_file_operations usb_ma901radio_fops = {
 	.owner		= THIS_MODULE,
 	.open		= v4l2_fh_open,
 	.release	= v4l2_fh_release,
 	.poll		= v4l2_ctrl_poll,
 	.unlocked_ioctl	= video_ioctl2,
 };

 static const struct v4l2_ioctl_ops usb_ma901radio_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_log_status  = v4l2_ctrl_log_status,
 	.vidioc_subscribe_event = v4l2_ctrl_subscribe_event,
 	.vidioc_unsubscribe_event = v4l2_event_unsubscribe,
 };

 static void usb_ma901radio_release(struct v4l2_device *v4l2_dev)
 {
 	struct ma901radio_device *radio = to_ma901radio_dev(v4l2_dev);

 	v4l2_ctrl_handler_free(&radio->hdl);
 	v4l2_device_unregister(&radio->v4l2_dev);
 	kfree(radio->buffer);
 	kfree(radio);
 }

 /* check if the device is present and register with v4l and usb if it is */
 static int usb_ma901radio_probe(struct usb_interface *intf,
 				const struct usb_device_id *id)
 {
 	struct usb_device *dev = interface_to_usbdev(intf);
 	struct ma901radio_device *radio;
 	int retval = 0;

 	/* Masterkit MA901 usb radio has the same USB ID as many others
 	 * Atmel V-USB devices. Let's make additional checks to be sure
 	 * that this is our device.
 	 */

 	if (dev->product && dev->manufacturer &&
 		(strncmp(dev->product, "MA901", 5) != 0
 		|| strncmp(dev->manufacturer, "www.masterkit.ru", 16) != 0))
 		return -ENODEV;

 	radio = kzalloc(sizeof(struct ma901radio_device), GFP_KERNEL);
 	if (!radio) {
 		dev_err(&intf->dev, "kzalloc for ma901radio_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;
 	}

 	v4l2_ctrl_handler_init(&radio->hdl, 1);

 	/* TODO:It looks like this radio doesn't have mute/unmute control
 	 * and windows program just emulate it using volume control.
 	 * Let's plan to do the same in this driver.
 	 *
 	 * v4l2_ctrl_new_std(&radio->hdl, &usb_ma901radio_ctrl_ops,
 	 *		  V4L2_CID_AUDIO_MUTE, 0, 1, 1, 1);
 	 */

 	v4l2_ctrl_new_std(&radio->hdl, &usb_ma901radio_ctrl_ops,
 			  V4L2_CID_AUDIO_VOLUME, MA901_VOLUME_MIN,
 			  MA901_VOLUME_MAX, 1, MA901_VOLUME_MAX);

 	if (radio->hdl.error) {
 		retval = radio->hdl.error;
 		dev_err(&intf->dev, "couldn't register control\n");
 		goto err_ctrl;
 	}
 	mutex_init(&radio->lock);

 	radio->v4l2_dev.ctrl_handler = &radio->hdl;
 	radio->v4l2_dev.release = usb_ma901radio_release;
 	strlcpy(radio->vdev.name, radio->v4l2_dev.name,
 		sizeof(radio->vdev.name));
 	radio->vdev.v4l2_dev = &radio->v4l2_dev;
 	radio->vdev.fops = &usb_ma901radio_fops;
 	radio->vdev.ioctl_ops = &usb_ma901radio_ioctl_ops;
 	radio->vdev.release = video_device_release_empty;
 	radio->vdev.lock = &radio->lock;
 	set_bit(V4L2_FL_USE_FH_PRIO, &radio->vdev.flags);

 	radio->usbdev = interface_to_usbdev(intf);
 	radio->intf = intf;
 	usb_set_intfdata(intf, &radio->v4l2_dev);
 	radio->curfreq = 95.21 * FREQ_MUL;

 	video_set_drvdata(&radio->vdev, radio);

 	/* TODO: we can get some statistics (freq, volume) from device
 	 * but it's not implemented yet. After insertion in usb-port radio
 	 * setups frequency and starts playing without any initialization.
 	 * So we don't call usb_ma901radio_init/get_stat() here.
 	 * retval = usb_ma901radio_init(radio);
 	 */

 	retval = video_register_device(&radio->vdev, 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_ctrl_handler_free(&radio->hdl);
 err_ctrl:
 	v4l2_device_unregister(&radio->v4l2_dev);
 err_v4l2:
 	kfree(radio->buffer);
 err_nobuf:
 	kfree(radio);
 err:
 	return retval;
 }

 /* USB Device ID List */
 static struct usb_device_id usb_ma901radio_device_table[] = {
 	{ USB_DEVICE_AND_INTERFACE_INFO(USB_MA901_VENDOR, USB_MA901_PRODUCT,
 							USB_CLASS_HID, 0, 0) },
 	{ }						/* Terminating entry */
 };

 MODULE_DEVICE_TABLE(usb, usb_ma901radio_device_table);

 /* USB subsystem interface */
 static struct usb_driver usb_ma901radio_driver = {
 	.name			= MA901_DRIVER_NAME,
 	.probe			= usb_ma901radio_probe,
 	.disconnect		= usb_ma901radio_disconnect,
 	.suspend		= usb_ma901radio_suspend,
 	.resume			= usb_ma901radio_resume,
 	.reset_resume		= usb_ma901radio_resume,
 	.id_table		= usb_ma901radio_device_table,
 };

 module_usb_driver(usb_ma901radio_driver);
	/*
	* Driver for the MasterKit MA901 USB FM radio. This device plugs
	* into the USB port and an analog audio input or headphones, so this thing
	* only deals with initialization, frequency setting, volume.
	*
	* Copyright (c) 2012 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
	*/

	#include <linux/kernel.h>
	#include <linux/module.h>
	#include <linux/init.h>
	#include <linux/slab.h>
	#include <linux/input.h>
	#include <linux/videodev2.h>
	#include <media/v4l2-device.h>
	#include <media/v4l2-ioctl.h>
	#include <media/v4l2-ctrls.h>
	#include <media/v4l2-event.h>
	#include <linux/usb.h>
	#include <linux/mutex.h>

	#define DRIVER_AUTHOR "Alexey Klimov <klimov.linux@gmail.com>"
	#define DRIVER_DESC "Masterkit MA901 USB FM radio driver"
	#define DRIVER_VERSION "0.0.1"

	MODULE_AUTHOR(DRIVER_AUTHOR);
	MODULE_DESCRIPTION(DRIVER_DESC);
	MODULE_LICENSE("GPL");
	MODULE_VERSION(DRIVER_VERSION);

	#define USB_MA901_VENDOR 0x16c0
	#define USB_MA901_PRODUCT 0x05df

	/* dev_warn macro with driver name */
	#define MA901_DRIVER_NAME "radio-ma901"
	#define ma901radio_dev_warn(dev, fmt, arg...) \
	dev_warn(dev, MA901_DRIVER_NAME " - " fmt, ##arg)

	#define ma901radio_dev_err(dev, fmt, arg...) \
	dev_err(dev, MA901_DRIVER_NAME " - " fmt, ##arg)

	/* Probably USB_TIMEOUT should be modified in module parameter */
	#define BUFFER_LENGTH 8
	#define USB_TIMEOUT 500

	#define FREQ_MIN 87.5
	#define FREQ_MAX 108.0
	#define FREQ_MUL 16000

	#define MA901_VOLUME_MAX 16
	#define MA901_VOLUME_MIN 0

	/* Commands that device should understand
	* List isn't full and will be updated with implementation of new functions
	*/
	#define MA901_RADIO_SET_FREQ 0x03
	#define MA901_RADIO_SET_VOLUME 0x04
	#define MA901_RADIO_SET_MONO_STEREO 0x05

	/* Comfortable defines for ma901radio_set_stereo */
	#define MA901_WANT_STEREO 0x50
	#define MA901_WANT_MONO 0xd0

	/* module parameter */
	static int radio_nr = -1;
	module_param(radio_nr, int, 0);
	MODULE_PARM_DESC(radio_nr, "Radio file number");

	/* Data for one (physical) device */
	struct ma901radio_device {
	/* reference to USB and video device */
	struct usb_device *usbdev;
	struct usb_interface *intf;
	struct video_device vdev;
	struct v4l2_device v4l2_dev;
	struct v4l2_ctrl_handler hdl;

	u8 *buffer;
	struct mutex lock; /* buffer locking */
	int curfreq;
	u16 volume;
	int stereo;
	bool muted;
	};

	static inline struct ma901radio_device to_ma901radio_dev(struct v4l2_device v4l2_dev)
	{
	return container_of(v4l2_dev, struct ma901radio_device, v4l2_dev);
	}

	/* set a frequency, freq is defined by v4l's TUNER_LOW, i.e. 1/16th kHz */
	static int ma901radio_set_freq(struct ma901radio_device *radio, int freq)
	{
	unsigned int freq_send = 0x300 + (freq >> 5) / 25;
	int retval;

	radio->buffer[0] = 0x0a;
	radio->buffer[1] = MA901_RADIO_SET_FREQ;
	radio->buffer[2] = ((freq_send >> 8) & 0xff) + 0x80;
	radio->buffer[3] = freq_send & 0xff;
	radio->buffer[4] = 0x00;
	radio->buffer[5] = 0x00;
	radio->buffer[6] = 0x00;
	radio->buffer[7] = 0x00;

	retval = usb_control_msg(radio->usbdev, usb_sndctrlpipe(radio->usbdev, 0),
	9, 0x21, 0x0300, 0,
	radio->buffer, BUFFER_LENGTH, USB_TIMEOUT);
	if (retval < 0)
	return retval;

	radio->curfreq = freq;
	return 0;
	}

	static int ma901radio_set_volume(struct ma901radio_device *radio, u16 vol_to_set)
	{
	int retval;

	radio->buffer[0] = 0x0a;
	radio->buffer[1] = MA901_RADIO_SET_VOLUME;
	radio->buffer[2] = 0xc2;
	radio->buffer[3] = vol_to_set + 0x20;
	radio->buffer[4] = 0x00;
	radio->buffer[5] = 0x00;
	radio->buffer[6] = 0x00;
	radio->buffer[7] = 0x00;

	retval = usb_control_msg(radio->usbdev, usb_sndctrlpipe(radio->usbdev, 0),
	9, 0x21, 0x0300, 0,
	radio->buffer, BUFFER_LENGTH, USB_TIMEOUT);
	if (retval < 0)
	return retval;

	radio->volume = vol_to_set;
	return retval;
	}

	static int ma901_set_stereo(struct ma901radio_device *radio, u8 stereo)
	{
	int retval;

	radio->buffer[0] = 0x0a;
	radio->buffer[1] = MA901_RADIO_SET_MONO_STEREO;
	radio->buffer[2] = stereo;
	radio->buffer[3] = 0x00;
	radio->buffer[4] = 0x00;
	radio->buffer[5] = 0x00;
	radio->buffer[6] = 0x00;
	radio->buffer[7] = 0x00;

	retval = usb_control_msg(radio->usbdev, usb_sndctrlpipe(radio->usbdev, 0),
	9, 0x21, 0x0300, 0,
	radio->buffer, BUFFER_LENGTH, USB_TIMEOUT);

	if (retval < 0)
	return retval;

	if (stereo == MA901_WANT_STEREO)
	radio->stereo = V4L2_TUNER_MODE_STEREO;
	else
	radio->stereo = V4L2_TUNER_MODE_MONO;

	return retval;
	}

	/* Handle unplugging the device.
	* We call video_unregister_device in any case.
	* The last function called in this procedure is
	* usb_ma901radio_device_release.
	*/
	static void usb_ma901radio_disconnect(struct usb_interface *intf)
	{
	struct ma901radio_device *radio = to_ma901radio_dev(usb_get_intfdata(intf));

	mutex_lock(&radio->lock);
	video_unregister_device(&radio->vdev);
	usb_set_intfdata(intf, NULL);
	v4l2_device_disconnect(&radio->v4l2_dev);
	mutex_unlock(&radio->lock);
	v4l2_device_put(&radio->v4l2_dev);
	}

	/* vidioc_querycap - query device capabilities */
	static int vidioc_querycap(struct file file, void priv,
	struct v4l2_capability *v)
	{
	struct ma901radio_device *radio = video_drvdata(file);

	strlcpy(v->driver, "radio-ma901", sizeof(v->driver));
	strlcpy(v->card, "Masterkit MA901 USB FM Radio", sizeof(v->card));
	usb_make_path(radio->usbdev, v->bus_info, sizeof(v->bus_info));
	v->device_caps = V4L2_CAP_RADIO \| V4L2_CAP_TUNER;
	v->capabilities = v->device_caps \| V4L2_CAP_DEVICE_CAPS;
	return 0;
	}

	/* vidioc_g_tuner - get tuner attributes */
	static int vidioc_g_tuner(struct file file, void priv,
	struct v4l2_tuner *v)
	{
	struct ma901radio_device *radio = video_drvdata(file);

	if (v->index > 0)
	return -EINVAL;

	v->signal = 0;

	/* TODO: the same words like in _probe() goes here.
	* When receiving of stats will be implemented then we can call
	* ma901radio_get_stat().
	* retval = ma901radio_get_stat(radio, &is_stereo, &v->signal);
	*/

	strcpy(v->name, "FM");
	v->type = V4L2_TUNER_RADIO;
	v->rangelow = FREQ_MIN * FREQ_MUL;
	v->rangehigh = FREQ_MAX * FREQ_MUL;
	v->capability = V4L2_TUNER_CAP_LOW \| V4L2_TUNER_CAP_STEREO;
	/* v->rxsubchans = is_stereo ? V4L2_TUNER_SUB_STEREO : V4L2_TUNER_SUB_MONO; */
	v->audmode = radio->stereo ?
	V4L2_TUNER_MODE_STEREO : V4L2_TUNER_MODE_MONO;
	return 0;
	}

	/* vidioc_s_tuner - set tuner attributes */
	static int vidioc_s_tuner(struct file file, void priv,
	const struct v4l2_tuner *v)
	{
	struct ma901radio_device *radio = video_drvdata(file);

	if (v->index > 0)
	return -EINVAL;

	/* mono/stereo selector */
	switch (v->audmode) {
	case V4L2_TUNER_MODE_MONO:
	return ma901_set_stereo(radio, MA901_WANT_MONO);
	default:
	return ma901_set_stereo(radio, MA901_WANT_STEREO);
	}
	}

	/* vidioc_s_frequency - set tuner radio frequency */
	static int vidioc_s_frequency(struct file file, void priv,
	const struct v4l2_frequency *f)
	{
	struct ma901radio_device *radio = video_drvdata(file);

	if (f->tuner != 0)
	return -EINVAL;

	return ma901radio_set_freq(radio, clamp_t(unsigned, f->frequency,
	FREQ_MIN * FREQ_MUL, FREQ_MAX * FREQ_MUL));
	}

	/* vidioc_g_frequency - get tuner radio frequency */
	static int vidioc_g_frequency(struct file file, void priv,
	struct v4l2_frequency *f)
	{
	struct ma901radio_device *radio = video_drvdata(file);

	if (f->tuner != 0)
	return -EINVAL;
	f->frequency = radio->curfreq;

	return 0;
	}

	static int usb_ma901radio_s_ctrl(struct v4l2_ctrl *ctrl)
	{
	struct ma901radio_device *radio =
	container_of(ctrl->handler, struct ma901radio_device, hdl);

	switch (ctrl->id) {
	case V4L2_CID_AUDIO_VOLUME: /* set volume */
	return ma901radio_set_volume(radio, (u16)ctrl->val);
	}

	return -EINVAL;
	}

	/* TODO: Should we really need to implement suspend and resume functions?
	* Radio has it's own memory and will continue playing if power is present
	* on usb port and on resume it will start to play again based on freq, volume
	* values in device memory.
	*/
	static int usb_ma901radio_suspend(struct usb_interface *intf, pm_message_t message)
	{
	return 0;
	}

	static int usb_ma901radio_resume(struct usb_interface *intf)
	{
	return 0;
	}

	static const struct v4l2_ctrl_ops usb_ma901radio_ctrl_ops = {
	.s_ctrl = usb_ma901radio_s_ctrl,
	};

	/* File system interface */
	static const struct v4l2_file_operations usb_ma901radio_fops = {
	.owner = THIS_MODULE,
	.open = v4l2_fh_open,
	.release = v4l2_fh_release,
	.poll = v4l2_ctrl_poll,
	.unlocked_ioctl = video_ioctl2,
	};

	static const struct v4l2_ioctl_ops usb_ma901radio_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_log_status = v4l2_ctrl_log_status,
	.vidioc_subscribe_event = v4l2_ctrl_subscribe_event,
	.vidioc_unsubscribe_event = v4l2_event_unsubscribe,
	};

	static void usb_ma901radio_release(struct v4l2_device *v4l2_dev)
	{
	struct ma901radio_device *radio = to_ma901radio_dev(v4l2_dev);

	v4l2_ctrl_handler_free(&radio->hdl);
	v4l2_device_unregister(&radio->v4l2_dev);
	kfree(radio->buffer);
	kfree(radio);
	}

	/* check if the device is present and register with v4l and usb if it is */
	static int usb_ma901radio_probe(struct usb_interface *intf,
	const struct usb_device_id *id)
	{
	struct usb_device *dev = interface_to_usbdev(intf);
	struct ma901radio_device *radio;
	int retval = 0;

	/* Masterkit MA901 usb radio has the same USB ID as many others
	* Atmel V-USB devices. Let's make additional checks to be sure
	* that this is our device.
	*/

	if (dev->product && dev->manufacturer &&
	(strncmp(dev->product, "MA901", 5) != 0
	\|\| strncmp(dev->manufacturer, "www.masterkit.ru", 16) != 0))
	return -ENODEV;

	radio = kzalloc(sizeof(struct ma901radio_device), GFP_KERNEL);
	if (!radio) {
	dev_err(&intf->dev, "kzalloc for ma901radio_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;
	}

	v4l2_ctrl_handler_init(&radio->hdl, 1);

	/* TODO:It looks like this radio doesn't have mute/unmute control
	* and windows program just emulate it using volume control.
	* Let's plan to do the same in this driver.
	*
	* v4l2_ctrl_new_std(&radio->hdl, &usb_ma901radio_ctrl_ops,
	* V4L2_CID_AUDIO_MUTE, 0, 1, 1, 1);
	*/

	v4l2_ctrl_new_std(&radio->hdl, &usb_ma901radio_ctrl_ops,
	V4L2_CID_AUDIO_VOLUME, MA901_VOLUME_MIN,
	MA901_VOLUME_MAX, 1, MA901_VOLUME_MAX);

	if (radio->hdl.error) {
	retval = radio->hdl.error;
	dev_err(&intf->dev, "couldn't register control\n");
	goto err_ctrl;
	}
	mutex_init(&radio->lock);

	radio->v4l2_dev.ctrl_handler = &radio->hdl;
	radio->v4l2_dev.release = usb_ma901radio_release;
	strlcpy(radio->vdev.name, radio->v4l2_dev.name,
	sizeof(radio->vdev.name));
	radio->vdev.v4l2_dev = &radio->v4l2_dev;
	radio->vdev.fops = &usb_ma901radio_fops;
	radio->vdev.ioctl_ops = &usb_ma901radio_ioctl_ops;
	radio->vdev.release = video_device_release_empty;
	radio->vdev.lock = &radio->lock;
	set_bit(V4L2_FL_USE_FH_PRIO, &radio->vdev.flags);

	radio->usbdev = interface_to_usbdev(intf);
	radio->intf = intf;
	usb_set_intfdata(intf, &radio->v4l2_dev);
	radio->curfreq = 95.21 * FREQ_MUL;

	video_set_drvdata(&radio->vdev, radio);

	/* TODO: we can get some statistics (freq, volume) from device
	* but it's not implemented yet. After insertion in usb-port radio
	* setups frequency and starts playing without any initialization.
	* So we don't call usb_ma901radio_init/get_stat() here.
	* retval = usb_ma901radio_init(radio);
	*/

	retval = video_register_device(&radio->vdev, 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_ctrl_handler_free(&radio->hdl);
	err_ctrl:
	v4l2_device_unregister(&radio->v4l2_dev);
	err_v4l2:
	kfree(radio->buffer);
	err_nobuf:
	kfree(radio);
	err:
	return retval;
	}

	/* USB Device ID List */
	static struct usb_device_id usb_ma901radio_device_table[] = {
	{ USB_DEVICE_AND_INTERFACE_INFO(USB_MA901_VENDOR, USB_MA901_PRODUCT,
	USB_CLASS_HID, 0, 0) },
	{ } /* Terminating entry */
	};

	MODULE_DEVICE_TABLE(usb, usb_ma901radio_device_table);

	/* USB subsystem interface */
	static struct usb_driver usb_ma901radio_driver = {
	.name = MA901_DRIVER_NAME,
	.probe = usb_ma901radio_probe,
	.disconnect = usb_ma901radio_disconnect,
	.suspend = usb_ma901radio_suspend,
	.resume = usb_ma901radio_resume,
	.reset_resume = usb_ma901radio_resume,
	.id_table = usb_ma901radio_device_table,
	};

	module_usb_driver(usb_ma901radio_driver);