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-Kernel driver pcf8574
-=====================
-
-Supported chips:
- * Philips PCF8574
- Prefix: 'pcf8574'
- Addresses scanned: none
- Datasheet: Publicly available at the Philips Semiconductors website
- http://www.semiconductors.philips.com/pip/PCF8574P.html
-
- * Philips PCF8574A
- Prefix: 'pcf8574a'
- Addresses scanned: none
- Datasheet: Publicly available at the Philips Semiconductors website
- http://www.semiconductors.philips.com/pip/PCF8574P.html
-
-Authors:
- Frodo Looijaard <frodol@dds.nl>,
- Philip Edelbrock <phil@netroedge.com>,
- Dan Eaton <dan.eaton@rocketlogix.com>,
- Aurelien Jarno <aurelien@aurel32.net>,
- Jean Delvare <khali@linux-fr.org>,
-
-
-Description
------------
-The PCF8574(A) is an 8-bit I/O expander for the I2C bus produced by Philips
-Semiconductors. It is designed to provide a byte I2C interface to up to 16
-separate devices (8 x PCF8574 and 8 x PCF8574A).
-
-This device consists of a quasi-bidirectional port. Each of the eight I/Os
-can be independently used as an input or output. To setup an I/O as an
-input, you have to write a 1 to the corresponding output.
-
-For more informations see the datasheet.
-
-
-Accessing PCF8574(A) via /sys interface
--------------------------------------
-
-The PCF8574(A) is plainly impossible to detect ! Stupid chip.
-So, you have to pass the I2C bus and address of the installed PCF857A
-and PCF8574A devices explicitly to the driver at load time via the
-force=... parameter.
-
-On detection (i.e. insmod, modprobe et al.), directories are being
-created for each detected PCF8574(A):
-
-/sys/bus/i2c/devices/<0>-<1>/
-where <0> is the bus the chip was detected on (e. g. i2c-0)
-and <1> the chip address ([20..27] or [38..3f]):
-
-(example: /sys/bus/i2c/devices/1-0020/)
-
-Inside these directories, there are two files each:
-read and write (and one file with chip name).
-
-The read file is read-only. Reading gives you the current I/O input
-if the corresponding output is set as 1, otherwise the current output
-value, that is to say 0.
-
-The write file is read/write. Writing a value outputs it on the I/O
-port. Reading returns the last written value. As it is not possible
-to read this value from the chip, you need to write at least once to
-this file before you can read back from it.