[media] em28xx: don't sleep on disconnect

The DVB framework will try to power-down an adapter that no-one is using
any more, but this assumes that the adapter is still connected to the
machine. That's not always true for a USB adapter, so disable the sleep
operations when the adapter has been physically unplugged.

This prevents I2C write failures with error -19 from appearing
occasionally in the dmesg log.

Signed-off-by: Chris Rankin <rankincj@yahoo.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/common/tuners/tda18271-fe.c

@@ -1230,7 +1230,7 @@ static int tda18271_set_config(struct dvb_frontend *fe, void *priv_cfg)
 	return 0;
 }
 
-static struct dvb_tuner_ops tda18271_tuner_ops = {
+static const struct dvb_tuner_ops tda18271_tuner_ops = {
 	.info = {
 		.name = "NXP TDA18271HD",
 		.frequency_min  =  45000000,

drivers/media/dvb/frontends/cxd2820r_core.c

@@ -742,7 +742,7 @@ static int cxd2820r_i2c_gate_ctrl(struct dvb_frontend *fe, int enable)
 	return cxd2820r_wr_reg_mask(priv, 0xdb, enable ? 1 : 0, 0x1);
 }
 
-static struct dvb_frontend_ops cxd2820r_ops[2];
+static const struct dvb_frontend_ops cxd2820r_ops[2];
 
 struct dvb_frontend *cxd2820r_attach(const struct cxd2820r_config *cfg,
 	struct i2c_adapter *i2c, struct dvb_frontend *fe)
@@ -796,7 +796,7 @@ error:
 }
 EXPORT_SYMBOL(cxd2820r_attach);
 
-static struct dvb_frontend_ops cxd2820r_ops[2] = {
+static const struct dvb_frontend_ops cxd2820r_ops[2] = {
 	{
 		/* DVB-T/T2 */
 		.info = {

drivers/media/video/em28xx/em28xx-dvb.c

@@ -842,6 +842,13 @@ out_free:
 	goto ret;
 }
 
+static inline void prevent_sleep(struct dvb_frontend_ops *ops)
+{
+	ops->set_voltage = NULL;
+	ops->sleep = NULL;
+	ops->tuner_ops.sleep = NULL;
+}
+
 static int em28xx_dvb_fini(struct em28xx *dev)
 {
 	if (!dev->board.has_dvb) {
@@ -850,8 +857,19 @@ static int em28xx_dvb_fini(struct em28xx *dev)
 	}
 
 	if (dev->dvb) {
-		em28xx_unregister_dvb(dev->dvb);
-		kfree(dev->dvb);
+		struct em28xx_dvb *dvb = dev->dvb;
+
+		if (dev->state & DEV_DISCONNECTED) {
+			/* We cannot tell the device to sleep
+			 * once it has been unplugged. */
+			if (dvb->fe[0])
+				prevent_sleep(&dvb->fe[0]->ops);
+			if (dvb->fe[1])
+				prevent_sleep(&dvb->fe[1]->ops);
+		}
+
+		em28xx_unregister_dvb(dvb);
+		kfree(dvb);
 		dev->dvb = NULL;
 	}