Gitweb:
http://git.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=80c002ddd2e732062e4371314d40515d0b5d8415
Commit: 80c002ddd2e732062e4371314d40515d0b5d8415
Parent: 941ed3b53086697eac7449f3ab5d2c5ab3259de2
Author: David Fries <[EMAIL PROTECTED]>
AuthorDate: Tue Jan 22 03:31:39 2008 -0800
Committer: Linus Torvalds <[EMAIL PROTECTED]>
CommitDate: Tue Jan 22 09:17:48 2008 -0800
W1: w1_therm.c is flagging 0C etc as invalid
The extra rom[0] check is flagging valid temperatures as invalid when
there is already a CRC data transmission check.
w1_therm_read_bin()
if (rom[8] == crc && rom[0])
verdict = 1;
Requiring rom[0] to be non-zero will flag as invalid temperature
conversions when the low byte is zero, specifically the temperatures 0C,
16C, 32C, 48C, -16C, -32C, and -48C.
The CRC check is produced on the device for the previous 8 bytes and is
required to ensure the data integrity in transmission. I don't see why the
extra check for rom[0] being non-zero is in there. Evgeniy Polyakov didn't
know either. Just for a check I unplugged the sensor, executed a
temperature conversion, and read the results. The read was all ff's, which
also failed the CRC, so it doesn't need to protect against a disconnected
sensor.
I have more extensive patches in the work, but these two trivial ones will
do for today. I would like to hear from people who use the ds2490 USB to
one wire dongle. 1 if you would be willing to test the patches as I
currently only have the one sensor on a short parisite powered wire, 2 if
there is any cheap sources for the ds2490.
Signed-off-by: David Fries <[EMAIL PROTECTED]>
Acked-by: Evgeniy Polyakov <[EMAIL PROTECTED]>
Signed-off-by: Andrew Morton <[EMAIL PROTECTED]>
Signed-off-by: Linus Torvalds <[EMAIL PROTECTED]>
---
drivers/w1/slaves/w1_therm.c | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)
diff --git a/drivers/w1/slaves/w1_therm.c b/drivers/w1/slaves/w1_therm.c
index feed89e..112f4ec 100644
--- a/drivers/w1/slaves/w1_therm.c
+++ b/drivers/w1/slaves/w1_therm.c
@@ -204,7 +204,7 @@ static ssize_t w1_therm_read_bin(struct kobject *kobj,
crc = w1_calc_crc8(rom, 8);
- if (rom[8] == crc && rom[0])
+ if (rom[8] == crc)
verdict = 1;
}
}
-
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