commit d05074b1beb66d40283228bd226f7244407375bb Author: David Fries <[EMAIL PROTECTED]> Date: Sat Jan 19 18:06:49 2008 -0600
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]> 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; } } -- David Fries <[EMAIL PROTECTED]> http://fries.net/~david/ (PGP encryption key available) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/