rtc: v3020: fix v3020_mmio_read_bit()

v3020_mmio_read_bit() always returns 0 when left_shift > 7.

v3020_mmio_read_bit()'s return type is (unsigned char).  The code returns
a value masked by (1 << left_shift) that is casted to the return type.  If
left_shift is larger than 7, the cast will always result in a 0 return
value.  The problem was discovered with left_shift = 16, and the included
patch corrects the problem.

The bug was introduced in the last (Apr 3 2009) commit of the file, kernel
versions 2.6.30 and later.

Cc: Alessandro Zummo <[email protected]>
Cc: Paul Gortmaker <[email protected]>
Cc: Raphael Assenat <[email protected]>
Cc: <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

diff --git a/drivers/rtc/rtc-v3020.c b/drivers/rtc/rtc-v3020.c
index ad164056feb6692cf7e66896a1c9f0d6b050b073..423cd5a30b10d2d5fa0dfe432e30f1d45eff91fd 100644 (file)
--- a/drivers/rtc/rtc-v3020.c
+++ b/drivers/rtc/rtc-v3020.c
@@ -96,7 +96,7 @@ static void v3020_mmio_write_bit(struct v3020 *chip, unsigned char bit)
 
 static unsigned char v3020_mmio_read_bit(struct v3020 *chip)
 {
-       return readl(chip->ioaddress) & (1 << chip->leftshift);
+       return !!(readl(chip->ioaddress) & (1 << chip->leftshift));
 }
 
 static struct v3020_chip_ops v3020_mmio_ops = {