Re: [lm-sensors] [PATCH] hwmon: (lm75) Strengthen detect function

[Guenter Roeck <linux@roeck-us.net>]

On 12/05/2014 03:57 AM, Jean Delvare wrote:
> Hi Guenter,
>
> On Thu,  4 Dec 2014 10:04:10 -0800, Guenter Roeck wrote:
>> A chip returning 0x00 in all registers is erroneously detected
>> as LM75. Check hysteresis and temperature limit registers and
>> abort if both are 0 to reduce the likelyhood for this to happen.
>>
>> Signed-off-by: Guenter Roeck <linux@roeck-us.net>
>> ---
>>   drivers/hwmon/lm75.c | 6 ++++++
>>   1 file changed, 6 insertions(+)
>>
>> diff --git a/drivers/hwmon/lm75.c b/drivers/hwmon/lm75.c
>> index f58439b..6753fd9 100644
>> --- a/drivers/hwmon/lm75.c
>> +++ b/drivers/hwmon/lm75.c
>> @@ -415,6 +415,12 @@ static int lm75_detect(struct i2c_client *new_client,
>>   		 || i2c_smbus_read_byte_data(new_client, 7) != os)
>>   			return -ENODEV;
>>   	}
>> +	/*
>> +	 * It is very unlikely that this is a LM75 if both
>> +	 * hysteresis and temperature limit registers are 0.
>> +	 */
>> +	if (hyst = 0 && os = 0)
>> +		return -ENODEV;
>>
>>   	/* Addresses cycling */
>>   	for (i = 8; i <= 248; i += 40) {
>
> Looks reasonable.
>
> Reviewed-by: Jean Delvare <jdelvare@suse.de>
>
> Did sensors-detect misdetect that chip as an LM75 too, or was the
> extended detection logic there good enough already?
>

Hi Jean,

sensors-detect is fine. Easy to test -load i2c-stub and see what
happens. I assume that is due to the "All registers hold same value"
test. Should I use that test instead ? I kind of prefer it.

Thanks,
Guenter


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