X-Git-Url: http://pilppa.org/gitweb/gitweb.cgi?a=blobdiff_plain;f=Documentation%2Fi2c%2Fchips%2Fpcf8574;h=235815c075ff5c8172b4641f8c74283890fbc7b5;hb=a993b542bb4cd3e5a64863b7ef892bbebec2239b;hp=2752c8ce3167c523eaf14bc82d975268cd502515;hpb=1bdf7a78c2b21fb94dfe7994dbe89310b18479d2;p=linux-2.6-omap-h63xx.git

diff --git a/Documentation/i2c/chips/pcf8574 b/Documentation/i2c/chips/pcf8574
index 2752c8ce316..235815c075f 100644
--- a/Documentation/i2c/chips/pcf8574
+++ b/Documentation/i2c/chips/pcf8574
@@ -4,13 +4,13 @@ Kernel driver pcf8574
 Supported chips:
   * Philips PCF8574
     Prefix: 'pcf8574'
-    Addresses scanned: I2C 0x20 - 0x27
+    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: I2C 0x38 - 0x3f
+    Addresses scanned: none
     Datasheet: Publicly available at the Philips Semiconductors website
                http://www.semiconductors.philips.com/pip/PCF8574P.html
 
@@ -38,12 +38,10 @@ For more informations see the datasheet.
 Accessing PCF8574(A) via /sys interface
 -------------------------------------
 
-! Be careful !
 The PCF8574(A) is plainly impossible to detect ! Stupid chip.
-So every chip with address in the interval [20..27] and [38..3f] are
-detected as PCF8574(A). If you have other chips in this address
-range, the workaround is to load this module after the one
-for your others chips.
+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):
@@ -62,8 +60,6 @@ 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.
-
-On module initialization the chip is configured as eight inputs (all
-outputs to 1), so you can connect any circuit to the PCF8574(A) without
-being afraid of short-circuit.
+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.