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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 <per.dalen@appeartv.com>
[guenter.roeck@ericsson.com: added second set of register reads]
Signed-off-by: Guenter Roeck <guenter.roeck@ericsson.com>
This commit is contained in:
Per Dalén 2011-05-26 09:08:53 -04:00 committed by Guenter Roeck
parent bb9973e4e7
commit 942c1a927b
1 changed files with 16 additions and 2 deletions
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18
drivers/hwmon/max6642.c
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@ -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);