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Subject[PATCH AUTOSEL 4.18 102/131] media: em28xx: Fix dual transport stream operation
From: Brad Love <>

[ Upstream commit a7853c257a3ea0907467a1750ff45de4d9ba1915 ]

Addresses the following, which introduced a regression itself:

Commit 509f89652f83 ("media: em28xx: fix a regression with HVR-950")

The regression fix breaks dual transport stream support. Currently,
when a tuner starts streaming it sets alt mode on the USB interface.
The problem is, in a dual tuner model, both tuners share the same
USB interface, so when the second tuner becomes active and sets alt
mode on the interface it kills streaming on the other port.

This patch addresses the regression by only setting alt mode
on the USB interface during em28xx_start_streaming, if the
device is not a dual tuner model. This allows all older and
single tuner devices to explicitly set alt mode during stream
startup. Testers report both isoc and bulk DualHD models work
correctly with the alt mode set only once, in em28xx_dvb_init.

Fixes: 509f89652f83 ("media: em28xx: fix a regression with HVR-950")
Signed-off-by: Brad Love <>
Signed-off-by: Michael Ira Krufky <>
Signed-off-by: Mauro Carvalho Chehab <>
Signed-off-by: Sasha Levin <>
drivers/media/usb/em28xx/em28xx-dvb.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/media/usb/em28xx/em28xx-dvb.c b/drivers/media/usb/em28xx/em28xx-dvb.c
index b778d8a1983e..a73faf12f7e4 100644
--- a/drivers/media/usb/em28xx/em28xx-dvb.c
+++ b/drivers/media/usb/em28xx/em28xx-dvb.c
@@ -218,7 +218,9 @@ static int em28xx_start_streaming(struct em28xx_dvb *dvb)
dvb_alt = dev->dvb_alt_isoc;

- usb_set_interface(udev, dev->ifnum, dvb_alt);
+ if (!dev->board.has_dual_ts)
+ usb_set_interface(udev, dev->ifnum, dvb_alt);
rc = em28xx_set_mode(dev, EM28XX_DIGITAL_MODE);
if (rc < 0)
return rc;
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