[PATCH] bttv: Don't unmask VPRES interrupt

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When the input is set to tuner and no antenna is connected, the BT848
can flood VPRES interrupts. So we don't want to enable this type of
interrupts when the input it set to tuner.

As we don't do anything when receiving such an interrupt anyway, the
easiest fix is to simply not unmask this specific interrupt.

Signed-off-by: Jean Delvare <khali@xxxxxxxxxxxx>
---
Long story:

While investigating a different bttv issue, I noticed that the
interrupt count of my bttv device (as shown in /proc/interrupts) was
increasing very quickly while I had not even opened the video device.
The interrupt rate could be well over 100/s (while it is usually around
75/s when I _do_ use the video device.) After enabling irq_debug in the
bttv driver, I found in the logs that the interrupts in question were
VPRES ones.

My BT878 adapter defaults to Television as its video input. I have no
antenna connected at this time, so I guess that the chip has a hard time
figuring out whether there's anything to decode, and as a result
switches quickly between video present and video not present.

For a reason I can't explain, I was not able to reproduce the problem
with kernels older than 2.6.21. All kernel versions since then have
exhibited the problem.

 drivers/media/video/bt8xx/bttv-driver.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- linux-2.6.27-rc5.orig/drivers/media/video/bt8xx/bttv-driver.c	2008-08-05 18:17:11.000000000 +0200
+++ linux-2.6.27-rc5/drivers/media/video/bt8xx/bttv-driver.c	2008-08-30 14:03:33.000000000 +0200
@@ -1368,7 +1368,7 @@ static void init_irqreg(struct bttv *btv
 			(btv->gpioirq ? BT848_INT_GPINT : 0) |
 			BT848_INT_SCERR |
 			(fdsr ? BT848_INT_FDSR : 0) |
-			BT848_INT_RISCI|BT848_INT_OCERR|BT848_INT_VPRES|
+			BT848_INT_RISCI | BT848_INT_OCERR |
 			BT848_INT_FMTCHG|BT848_INT_HLOCK|
 			BT848_INT_I2CDONE,
 			BT848_INT_MASK);


-- 
Jean Delvare

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