From dfe1645a5a48f4a40ace528e5de627c1cc74cb78 Mon Sep 17 00:00:00 2001
From: Jean Delvare <khali@linux-fr.org>
Date: Sun, 14 Nov 2004 14:34:30 +0000
Subject: [PATCH] Detect the Philips PCA9556 (8-bit I/O expander).

git-svn-id: http://lm-sensors.org/svn/lm-sensors/trunk@2755 7894878c-1315-0410-8ee3-d5d059ff63e0
---
 prog/detect/sensors-detect | 37 ++++++++++++++++++++++++++++++++++++-
 1 file changed, 36 insertions(+), 1 deletion(-)

diff --git a/prog/detect/sensors-detect b/prog/detect/sensors-detect
index 09355685..d60fd16b 100755
--- a/prog/detect/sensors-detect
+++ b/prog/detect/sensors-detect
@@ -836,7 +836,7 @@ use subs qw(mtp008_detect lm78_detect lm78_isa_detect lm78_alias_detect
             fscher_detect adm1029_detect adm1031_detect max6900_detect
             m5879_detect pca9540_detect smartbatt_mgr_detect
             smartbatt_chgr_detect adt7467_detect lm92_detect max1619_detect
-            lm93_detect lm77_detect lm63_detect);
+            lm93_detect lm77_detect lm63_detect pca9556_detect);
 
 # This is a list of all recognized chips. 
 # Each entry must have the following fields:
@@ -1387,6 +1387,12 @@ use subs qw(mtp008_detect lm78_detect lm78_isa_detect lm78_alias_detect
        i2c_addrs => [0x70],
        i2c_detect => sub { pca9540_detect @_ },
      },
+     {
+       name => "Philips Semiconductors PCA9556",
+       driver => "to-be-written",
+       i2c_addrs => [0x18..0x1f],
+       i2c_detect => sub { pca9556_detect @_ },
+     },
      {
        name => "Maxim MAX6900",
        driver => "to-be-written",
@@ -4185,6 +4191,35 @@ sub pca9540_detect
 	return 1;
 }
 
+# $_[0]: A reference to the file descriptor to access this chip.
+#        We assume an i2c_set_slave_addr was already done.
+# $_[1]: Address (unused)
+# Returns: undef if not detected, 1 if detected
+# Detection is rather difficult, since the PCA9556 only has 4 registers
+# and no unused bit. We use the fact that the registers cycle over
+# 4 addresses boundaries, and the logic rules between registers.
+sub pca9556_detect
+{
+	my ($file, $addr) = @_;
+	my $input = i2c_smbus_read_byte_data($file, 0x00);
+	my $output = i2c_smbus_read_byte_data($file, 0x01);
+	my $invert = i2c_smbus_read_byte_data($file, 0x02);
+	my $config = i2c_smbus_read_byte_data($file, 0x03);
+
+	# Pins configured for output (config = 0) must obey the following
+	# rule: input = output ^ invert
+
+	return unless ($input & ~$config) == (($output ^ $invert) & ~$config);
+
+	for (my $i = 5; $i < 254 ; $i+=4) {
+		return unless i2c_smbus_read_byte_data($file, $i) == $output;
+		return unless i2c_smbus_read_byte_data($file, $i+1) == $invert;
+		return unless i2c_smbus_read_byte_data($file, $i+2) == $config;
+	}
+
+	return 1;
+}
+
 # $_[0]: A reference to the file descriptor to access this chip.
 #        We may assume an i2c_set_slave_addr was already done.
 # $_[1]: Address