From 942c1a927bf296fd64fd49f04c5a8f66bb14446b Mon Sep 17 00:00:00 2001 From: =?utf8?q?Per=20Dal=C3=A9n?= Date: Thu, 26 May 2011 09:08:53 -0400 Subject: [PATCH] hwmon: (max6642): Better chip detection schema Improve detection of MAX6642 by reading non existing registers (0x04, 0x06 and 0xff). Reading those registers returns the previously read value. Signed-off-by: Per Dalen [guenter.roeck@ericsson.com: added second set of register reads] Signed-off-by: Guenter Roeck --- drivers/hwmon/max6642.c | 18 ++++++++++++++++-- 1 file changed, 16 insertions(+), 2 deletions(-) diff --git a/drivers/hwmon/max6642.c b/drivers/hwmon/max6642.c index 0f30e1bb366f..e855d3b0bd1f 100644 --- a/drivers/hwmon/max6642.c +++ b/drivers/hwmon/max6642.c @@ -136,15 +136,29 @@ static int max6642_detect(struct i2c_client *client, if (man_id != 0x4D) return -ENODEV; + /* sanity check */ + if (i2c_smbus_read_byte_data(client, 0x04) != 0x4D + || i2c_smbus_read_byte_data(client, 0x06) != 0x4D + || i2c_smbus_read_byte_data(client, 0xff) != 0x4D) + return -ENODEV; + /* * We read the config and status register, the 4 lower bits in the * config register should be zero and bit 5, 3, 1 and 0 should be * zero in the status register. */ reg_config = i2c_smbus_read_byte_data(client, MAX6642_REG_R_CONFIG); + if ((reg_config & 0x0f) != 0x00) + return -ENODEV; + + /* in between, another round of sanity checks */ + if (i2c_smbus_read_byte_data(client, 0x04) != reg_config + || i2c_smbus_read_byte_data(client, 0x06) != reg_config + || i2c_smbus_read_byte_data(client, 0xff) != reg_config) + return -ENODEV; + reg_status = i2c_smbus_read_byte_data(client, MAX6642_REG_R_STATUS); - if (((reg_config & 0x0f) != 0x00) || - ((reg_status & 0x2b) != 0x00)) + if ((reg_status & 0x2b) != 0x00) return -ENODEV; strlcpy(info->type, "max6642", I2C_NAME_SIZE); -- 2.20.1