Per datasheet, SHT4x may need up to 8.2ms for a "high repeatability"
measurement to complete. Attempting to read the result too early
triggers a NAK which then causes an EREMOTEIO error.
This behavior has been confirmed with a logic analyzer while running
the I2C bus at only 40kHz. The low frequency precludes any
signal-integrity issues, which was also confirmed by the absence of
any CRC8 errors. In this configuration, a NAK occurred on any read
that followed the measurement command within less than 8.2ms.
Signed-off-by: David Mosberger-Tang <davidm@egauge.net>
Link: https://lore.kernel.org/r/20211120212849.2300854-2-davidm@egauge.net
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Kernel doc for sht4x_read_values() shows 0 on success, 1 on failure but
the return value on success is actually always positive as it is set to
SHT4X_RESPONSE_LENGTH by a successful call to i2c_master_recv().
Miscellanea:
o Update the kernel doc for sht4x_read_values to 0 for success or -ERRNO
o Remove incorrectly used kernel doc /** header for other _read functions
o Typo fix succesfull->successful
o Reverse a test to unindent a block and use goto unlock
o Declare cmd[SHT4X_CMD_LEN] rather than cmd[]
At least for gcc 10.2, object size is reduced a tiny bit.
$ size drivers/hwmon/sht4x.o*
text data bss dec hex filename
1752 404 256 2412 96c drivers/hwmon/sht4x.o.new
1825 404 256 2485 9b5 drivers/hwmon/sht4x.o.old
Signed-off-by: Joe Perches <joe@perches.com>
Link: https://lore.kernel.org/r/60eedce497137eb34448c0c77e01ec9d9c972ad7.camel@perches.com
Reviewed by: Navin Sankar Velliangiri <navin@linumiz.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
This patch adds a hwmon driver for the SHT4x Temperature and
Humidity sensor.
Signed-off-by: Navin Sankar Velliangiri <navin@linumiz.com>
[groeck: dropped unnecessary empty line and continuation lines]
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
