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.
        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
    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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