V4L/DVB (9227): MFE: Add multi-frontend mutual exclusion

This add frontend R/W mutual exclusion.
Prior to this point in time it was possible to open both
frontends simultaneously which an MFE card cannot support.

In order to stop this, a delayed open is performed which
has the following function:

-  Return EBUSY after a configurable amount of time
   if a frontend is unavailable due to the other being
   in use.

-  Only allow opening of a frontend if the kernel thread
   of the other has stopped.

This solution was chosen to allow switching between
frontends to work as seamlessly as possible. When both
frontends are actually opened simultaneously then one
will only open, but if quick switching is performed
between one of many then the new open will succeed in
a clean fashion rather than interrupting a kernel
thread.

Signed-off-by: Darron Broad <darron@kewl.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/dvb/dvb-core/dvb_frontend.c

@@ -47,6 +47,7 @@ static int dvb_shutdown_timeout;
 static int dvb_force_auto_inversion;
 static int dvb_override_tune_delay;
 static int dvb_powerdown_on_sleep = 1;
+static int dvb_mfe_wait_time = 5;
 
 module_param_named(frontend_debug, dvb_frontend_debug, int, 0644);
 MODULE_PARM_DESC(frontend_debug, "Turn on/off frontend core debugging (default:off).");
@@ -58,6 +59,8 @@ module_param(dvb_override_tune_delay, int, 0644);
 MODULE_PARM_DESC(dvb_override_tune_delay, "0: normal (default), >0 => delay in milliseconds to wait for lock after a tune attempt");
 module_param(dvb_powerdown_on_sleep, int, 0644);
 MODULE_PARM_DESC(dvb_powerdown_on_sleep, "0: do not power down, 1: turn LNB voltage off on sleep (default)");
+module_param(dvb_mfe_wait_time, int, 0644);
+MODULE_PARM_DESC(dvb_mfe_wait_time, "Wait up to <mfe_wait_time> seconds on open() for multi-frontend to become available (default:5 seconds)");
 
 #define dprintk if (dvb_frontend_debug) printk
 
@@ -1706,13 +1709,46 @@ static int dvb_frontend_open(struct inode *inode, struct file *file)
 	struct dvb_device *dvbdev = file->private_data;
 	struct dvb_frontend *fe = dvbdev->priv;
 	struct dvb_frontend_private *fepriv = fe->frontend_priv;
+	struct dvb_adapter *adapter = fe->dvb;
+	struct dvb_device *mfedev;
+	struct dvb_frontend *mfe;
+	struct dvb_frontend_private *mfepriv;
+	int mferetry;
 	int ret;
 
 	dprintk ("%s\n", __func__);
 
+	if (adapter->mfe_shared) {
+		mutex_lock (&adapter->mfe_lock);
+		if (adapter->mfe_dvbdev != dvbdev) {
+			if (adapter->mfe_dvbdev) {
+				mfedev = adapter->mfe_dvbdev;
+				mfe = mfedev->priv;
+				mfepriv = mfe->frontend_priv;
+				mutex_unlock (&adapter->mfe_lock);
+				mferetry = (dvb_mfe_wait_time << 1);
+				while (mferetry-- && (mfedev->users != -1 || mfepriv->thread != NULL)) {
+					if(msleep_interruptible(500)) {
+						if(signal_pending(current))
+							return -EINTR;
+					}
+				}
+				mutex_lock (&adapter->mfe_lock);
+				mfedev = adapter->mfe_dvbdev;
+				mfe = mfedev->priv;
+				mfepriv = mfe->frontend_priv;
+				if (mfedev->users != -1 || mfepriv->thread != NULL) {
+					ret = -EBUSY;
+					goto err0;
+				}
+			}
+			adapter->mfe_dvbdev = dvbdev;
+		}
+	}
+
 	if (dvbdev->users == -1 && fe->ops.ts_bus_ctrl) {
 		if ((ret = fe->ops.ts_bus_ctrl(fe, 1)) < 0)
-			return ret;
+			goto err0;
 	}
 
 	if ((ret = dvb_generic_open (inode, file)) < 0)
@@ -1732,13 +1768,18 @@ static int dvb_frontend_open(struct inode *inode, struct file *file)
 		fepriv->events.eventr = fepriv->events.eventw = 0;
 	}
 
+	if (adapter->mfe_shared)
+		mutex_unlock (&adapter->mfe_lock);
 	return ret;
 
 err2:
 	dvb_generic_release(inode, file);
 err1:
 	if (dvbdev->users == -1 && fe->ops.ts_bus_ctrl)
 		fe->ops.ts_bus_ctrl(fe, 0);
+err0:
+	if (adapter->mfe_shared)
+		mutex_unlock (&adapter->mfe_lock);
 	return ret;
 }
 

drivers/media/dvb/dvb-core/dvbdev.c

@@ -326,6 +326,9 @@ int dvb_register_adapter(struct dvb_adapter *adap, const char *name,
 	adap->name = name;
 	adap->module = module;
 	adap->device = device;
+	adap->mfe_shared = 0;
+	adap->mfe_dvbdev = NULL;
+	mutex_init (&adap->mfe_lock);
 
 	list_add_tail (&adap->list_head, &dvb_adapter_list);
 

drivers/media/dvb/dvb-core/dvbdev.h

@@ -62,6 +62,10 @@ struct dvb_adapter {
 	struct device *device;
 
 	struct module *module;
+
+	int mfe_shared;			/* indicates mutually exclusive frontends */
+	struct dvb_device *mfe_dvbdev;	/* frontend device in use */
+	struct mutex mfe_lock;		/* access lock for thread creation */
 };
 
 

drivers/media/video/cx23885/cx23885-dvb.c

@@ -556,7 +556,7 @@ static int dvb_register(struct cx23885_tsport *port)
 
 	/* register everything */
 	return videobuf_dvb_register_bus(&port->frontends, THIS_MODULE, port,
-				     &dev->pci->dev, adapter_nr);
+		&dev->pci->dev, adapter_nr, 0);
 
 }
 

drivers/media/video/cx88/cx88-dvb.c

@@ -594,14 +594,9 @@ static struct stv0288_config tevii_tuner_earda_config = {
 
 static int dvb_register(struct cx8802_dev *dev)
 {
-	//struct cx88_core *core = dev->core;
-
-	///* init struct videobuf_dvb */
-	//fe->dvb.name = core->name;
-	//dev->ts_gen_cntrl = 0x0c;
-
 	struct cx88_core *core = dev->core;
 	struct videobuf_dvb_frontend *fe0, *fe1 = NULL;
+	int mfe_shared = 0; /* bus not shared by default */
 
 	/* Get the first frontend */
 	fe0 = videobuf_dvb_get_frontend(&dev->frontends, 1);
@@ -669,6 +664,7 @@ static int dvb_register(struct cx8802_dev *dev)
 		fe1 = videobuf_dvb_get_frontend(&dev->frontends, 2);
 		if (fe1) {
 			dev->frontends.gate = 2;
+			mfe_shared = 1;
 			fe1->dvb.frontend = dvb_attach(cx22702_attach,
 				&hauppauge_hvr_config,
 				&dev->core->i2c_adap);
@@ -1013,6 +1009,7 @@ static int dvb_register(struct cx8802_dev *dev)
 		fe1 = videobuf_dvb_get_frontend(&dev->frontends, 2);
 		if (fe1) {
 			dev->frontends.gate = 2;
+			mfe_shared = 1;
 			fe1->dvb.frontend = dvb_attach(cx22702_attach,
 				&hauppauge_hvr_config,
 				&dev->core->i2c_adap);
@@ -1110,7 +1107,7 @@ static int dvb_register(struct cx8802_dev *dev)
 
 	/* register everything */
 	return videobuf_dvb_register_bus(&dev->frontends, THIS_MODULE, dev,
-		&dev->pci->dev, adapter_nr);
+		&dev->pci->dev, adapter_nr, mfe_shared);
 
 frontend_detach:
 	if (fe0->dvb.frontend) {

drivers/media/video/saa7134/saa7134-dvb.c

@@ -1395,7 +1395,7 @@ static int dvb_init(struct saa7134_dev *dev)
 
 	/* register everything else */
 	ret = videobuf_dvb_register_bus(&dev->frontends, THIS_MODULE, dev,
-		&dev->pci->dev, adapter_nr);
+		&dev->pci->dev, adapter_nr, 0);
 
 	/* this sequence is necessary to make the tda1004x load its firmware
 	 * and to enter analog mode of hybrid boards

drivers/media/video/videobuf-dvb.c

@@ -140,7 +140,8 @@ int videobuf_dvb_register_bus(struct videobuf_dvb_frontends *f,
 			  struct module *module,
 			  void *adapter_priv,
 			  struct device *device,
-			  short *adapter_nr) //NEW
+			  short *adapter_nr,
+			  int mfe_shared)
 {
 	struct list_head *list, *q;
 	struct videobuf_dvb_frontend *fe;
@@ -153,7 +154,7 @@ int videobuf_dvb_register_bus(struct videobuf_dvb_frontends *f,
 	}
 
 	/* Bring up the adapter */
-	res = videobuf_dvb_register_adapter(f, module, adapter_priv, device, fe->dvb.name, adapter_nr); //NEW
+	res = videobuf_dvb_register_adapter(f, module, adapter_priv, device, fe->dvb.name, adapter_nr, mfe_shared);
 	if (res < 0) {
 		printk(KERN_WARNING "videobuf_dvb_register_adapter failed (errno = %d)\n", res);
 		goto err;
@@ -181,7 +182,8 @@ int videobuf_dvb_register_adapter(struct videobuf_dvb_frontends *fe,
 			  void *adapter_priv,
 			  struct device *device,
 			  char *adapter_name,
-			  short *adapter_nr) //NEW
+			  short *adapter_nr,
+			  int mfe_shared)
 {
 	int result;
 
@@ -194,6 +196,7 @@ int videobuf_dvb_register_adapter(struct videobuf_dvb_frontends *fe,
 		       adapter_name, result);
 	}
 	fe->adapter.priv = adapter_priv;
+	fe->adapter.mfe_shared = mfe_shared;
 
 	return result;
 }

include/media/videobuf-dvb.h

@@ -43,7 +43,8 @@ int videobuf_dvb_register_bus(struct videobuf_dvb_frontends *f,
 			  struct module *module,
 			  void *adapter_priv,
 			  struct device *device,
-			  short *adapter_nr);   //NEW
+			  short *adapter_nr,
+			  int mfe_shared);
 
 void videobuf_dvb_unregister_bus(struct videobuf_dvb_frontends *f);
 
@@ -52,7 +53,8 @@ int videobuf_dvb_register_adapter(struct videobuf_dvb_frontends *f,
 			  void *adapter_priv,
 			  struct device *device,
 			  char *adapter_name,
-			  short *adapter_nr);   //NEW
+			  short *adapter_nr,
+			  int mfe_shared);
 
 int videobuf_dvb_register_frontend(struct dvb_adapter *adapter, struct videobuf_dvb *dvb);