V4L/DVB (7401): radio-si470x: unplugging fixed

This patch fixes several kernel oops, when unplugging device while it is in
use:

Basically the patch delays freeing of the internal variables in
si470x_usb_driver_disconnect, until the the last user closed the device in
si470x_fops_release. This was implemented a while ago with the help of Oliver
Neukum.

I tested the patch five times (unplugging while in use) without oops coming
from the radio-si470x driver anymore. A remaining oops was coming from the
usbaudio driver, but this is someone else task. Hopefully this fixed all
unplugging issues.

Signed-off-by: Tobias Lorenz <tobias.lorenz@gmx.net>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>

drivers/media/radio/radio-si470x.c

@@ -85,6 +85,7 @@
  *		Oliver Neukum <oliver@neukum.org>
  *		Version 1.0.7
  *		- usb autosuspend support
+ *             - unplugging fixed
  *
  * ToDo:
  * - add seeking support
@@ -97,10 +98,10 @@
 /* driver definitions */
 #define DRIVER_AUTHOR "Tobias Lorenz <tobias.lorenz@gmx.net>"
 #define DRIVER_NAME "radio-si470x"
-#define DRIVER_KERNEL_VERSION KERNEL_VERSION(1, 0, 6)
+#define DRIVER_KERNEL_VERSION KERNEL_VERSION(1, 0, 7)
 #define DRIVER_CARD "Silicon Labs Si470x FM Radio Receiver"
 #define DRIVER_DESC "USB radio driver for Si470x FM Radio Receivers"
-#define DRIVER_VERSION "1.0.6"
+#define DRIVER_VERSION "1.0.7"
 
 
 /* kernel includes */
@@ -424,6 +425,7 @@ struct si470x_device {
 
 	/* driver management */
 	unsigned int users;
+       unsigned char disconnected;
 
 	/* Silabs internal registers (0..15) */
 	unsigned short registers[RADIO_REGISTER_NUM];
@@ -439,6 +441,12 @@ struct si470x_device {
 };
 
 
+/*
+ * Lock to prevent kfree of data before all users have releases the device.
+ */
+static DEFINE_MUTEX(open_close_lock);
+
+
 /*
  * The frequency is set in units of 62.5 Hz when using V4L2_TUNER_CAP_LOW,
  * 62.5 kHz otherwise.
@@ -577,7 +585,7 @@ static int si470x_get_rds_registers(struct si470x_device *radio)
 		usb_rcvintpipe(radio->usbdev, 1),
 		(void *) &buf, sizeof(buf), &size, usb_timeout);
 	if (size != sizeof(buf))
-		printk(KERN_WARNING DRIVER_NAME ": si470x_get_rds_register: "
+	       printk(KERN_WARNING DRIVER_NAME ": si470x_get_rds_registers: "
 			"return size differs: %d != %zu\n", size, sizeof(buf));
 	if (retval < 0)
 		printk(KERN_WARNING DRIVER_NAME ": si470x_get_rds_registers: "
@@ -875,6 +883,8 @@ static void si470x_work(struct work_struct *work)
 	struct si470x_device *radio = container_of(work, struct si470x_device,
 		work.work);
 
+       if (radio->disconnected)
+	       return;
 	if ((radio->registers[SYSCONFIG1] & SYSCONFIG1_RDS) == 0)
 		return;
 
@@ -1001,13 +1011,21 @@ static int si470x_fops_open(struct inode *inode, struct file *file)
 static int si470x_fops_release(struct inode *inode, struct file *file)
 {
 	struct si470x_device *radio = video_get_drvdata(video_devdata(file));
-	int retval;
+       int retval = 0;
 
 	if (!radio)
 		return -ENODEV;
 
+       mutex_lock(&open_close_lock);
 	radio->users--;
 	if (radio->users == 0) {
+	       if (radio->disconnected) {
+		       video_unregister_device(radio->videodev);
+		       kfree(radio->buffer);
+		       kfree(radio);
+		       goto done;
+	       }
+
 		/* stop rds reception */
 		cancel_delayed_work_sync(&radio->work);
 
@@ -1016,10 +1034,11 @@ static int si470x_fops_release(struct inode *inode, struct file *file)
 
 		retval = si470x_stop(radio);
 		usb_autopm_put_interface(radio->intf);
-		return retval;
 	}
 
-	return 0;
+done:
+       mutex_unlock(&open_close_lock);
+       return retval;
 }
 
 
@@ -1157,6 +1176,9 @@ static int si470x_vidioc_g_ctrl(struct file *file, void *priv,
 {
 	struct si470x_device *radio = video_get_drvdata(video_devdata(file));
 
+       if (radio->disconnected)
+	       return -EIO;
+
 	switch (ctrl->id) {
 	case V4L2_CID_AUDIO_VOLUME:
 		ctrl->value = radio->registers[SYSCONFIG2] &
@@ -1181,6 +1203,9 @@ static int si470x_vidioc_s_ctrl(struct file *file, void *priv,
 	struct si470x_device *radio = video_get_drvdata(video_devdata(file));
 	int retval;
 
+       if (radio->disconnected)
+	       return -EIO;
+
 	switch (ctrl->id) {
 	case V4L2_CID_AUDIO_VOLUME:
 		radio->registers[SYSCONFIG2] &= ~SYSCONFIG2_VOLUME;
@@ -1243,6 +1268,8 @@ static int si470x_vidioc_g_tuner(struct file *file, void *priv,
 	struct si470x_device *radio = video_get_drvdata(video_devdata(file));
 	int retval;
 
+       if (radio->disconnected)
+	       return -EIO;
 	if (tuner->index > 0)
 		return -EINVAL;
 
@@ -1299,6 +1326,8 @@ static int si470x_vidioc_s_tuner(struct file *file, void *priv,
 	struct si470x_device *radio = video_get_drvdata(video_devdata(file));
 	int retval;
 
+       if (radio->disconnected)
+	       return -EIO;
 	if (tuner->index > 0)
 		return -EINVAL;
 
@@ -1324,6 +1353,9 @@ static int si470x_vidioc_g_frequency(struct file *file, void *priv,
 {
 	struct si470x_device *radio = video_get_drvdata(video_devdata(file));
 
+       if (radio->disconnected)
+	       return -EIO;
+
 	freq->type = V4L2_TUNER_RADIO;
 	freq->frequency = si470x_get_freq(radio);
 
@@ -1340,6 +1372,8 @@ static int si470x_vidioc_s_frequency(struct file *file, void *priv,
 	struct si470x_device *radio = video_get_drvdata(video_devdata(file));
 	int retval;
 
+       if (radio->disconnected)
+	       return -EIO;
 	if (freq->type != V4L2_TUNER_RADIO)
 		return -EINVAL;
 
@@ -1510,11 +1544,16 @@ static void si470x_usb_driver_disconnect(struct usb_interface *intf)
 {
 	struct si470x_device *radio = usb_get_intfdata(intf);
 
+       mutex_lock(&open_close_lock);
+       radio->disconnected = 1;
 	cancel_delayed_work_sync(&radio->work);
 	usb_set_intfdata(intf, NULL);
+       if (radio->users == 0) {
 	       video_unregister_device(radio->videodev);
 	       kfree(radio->buffer);
 	       kfree(radio);
+       }
+       mutex_unlock(&open_close_lock);
 }