[PATCH] hwmon: (nct6775) Do not accept force_id unless chip is found

[PATCH] hwmon: (nct6775) Do not accept force_id unless chip is found

[Guenter Roeck]

Since commit 698a7c24a544 ("hwmon: (nct6775) Support two SuperIO chips
in the same system"), the driver supports two Super-IO chips. This has
the undesirable side effect that force_id always detects a second chip
at address 0xfff8, even if no chip exists at that address.

nct6775: Found NCT6793D or compatible chip at 0x4e:0xfff8

If no chip at all is found at a given SIO address, it does not make sense
to instantiate it. Limit force_id to only work if some chip is found,
that is if the chip ID returns a value other than 0xffff.

Signed-off-by: Guenter Roeck <linux@roeck-us.net>
---
 drivers/hwmon/nct6775.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/hwmon/nct6775.c b/drivers/hwmon/nct6775.c
index d087a8e00cf5..7859a30ce31e 100644
--- a/drivers/hwmon/nct6775.c
+++ b/drivers/hwmon/nct6775.c
@@ -4232,11 +4232,11 @@ static int __init nct6775_find(int sioaddr, struct nct6775_sio_data *sio_data)
 	if (err)
 		return err;
 
-	if (force_id)
+	val = (superio_inb(sioaddr, SIO_REG_DEVID) << 8) |
+		superio_inb(sioaddr, SIO_REG_DEVID + 1);
+	if (force_id && val != 0xffff)
 		val = force_id;
-	else
-		val = (superio_inb(sioaddr, SIO_REG_DEVID) << 8)
-		    | superio_inb(sioaddr, SIO_REG_DEVID + 1);
+
 	switch (val & SIO_ID_MASK) {
 	case SIO_NCT6106_ID:
 		sio_data->kind = nct6106;
-- 
2.5.0

Re: [PATCH] hwmon: (nct6775) Do not accept force_id unless chip is found

[Jean Delvare]

Hi Guenter,

On Wed,  3 Aug 2016 22:15:37 -0700, Guenter Roeck wrote:
> Since commit 698a7c24a544 ("hwmon: (nct6775) Support two SuperIO chips
> in the same system"), the driver supports two Super-IO chips. This has
> the undesirable side effect that force_id always detects a second chip
> at address 0xfff8, even if no chip exists at that address.
> 
> nct6775: Found NCT6793D or compatible chip at 0x4e:0xfff8
> 
> If no chip at all is found at a given SIO address, it does not make sense
> to instantiate it. Limit force_id to only work if some chip is found,
> that is if the chip ID returns a value other than 0xffff.

Agreed, good catch.

> 
> Signed-off-by: Guenter Roeck <linux@roeck-us.net>
> ---
>  drivers/hwmon/nct6775.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/hwmon/nct6775.c b/drivers/hwmon/nct6775.c
> index d087a8e00cf5..7859a30ce31e 100644
> --- a/drivers/hwmon/nct6775.c
> +++ b/drivers/hwmon/nct6775.c
> @@ -4232,11 +4232,11 @@ static int __init nct6775_find(int sioaddr, struct nct6775_sio_data *sio_data)
>  	if (err)
>  		return err;
>  
> -	if (force_id)
> +	val = (superio_inb(sioaddr, SIO_REG_DEVID) << 8) |
> +		superio_inb(sioaddr, SIO_REG_DEVID + 1);
> +	if (force_id && val != 0xffff)
>  		val = force_id;
> -	else
> -		val = (superio_inb(sioaddr, SIO_REG_DEVID) << 8)
> -		    | superio_inb(sioaddr, SIO_REG_DEVID + 1);
> +
>  	switch (val & SIO_ID_MASK) {
>  	case SIO_NCT6106_ID:
>  		sio_data->kind = nct6106;

Reviewed-by: Jean Delvare <jdelvare@suse.de>

-- 
Jean Delvare
SUSE L3 Support

Re: [PATCH] hwmon: (nct6775) Do not accept force_id unless chip is found

[Guenter Roeck]

On 08/04/2016 04:00 AM, Jean Delvare wrote:
> Hi Guenter,
>
> On Wed,  3 Aug 2016 22:15:37 -0700, Guenter Roeck wrote:
>> Since commit 698a7c24a544 ("hwmon: (nct6775) Support two SuperIO chips
>> in the same system"), the driver supports two Super-IO chips. This has
>> the undesirable side effect that force_id always detects a second chip
>> at address 0xfff8, even if no chip exists at that address.
>>
>> nct6775: Found NCT6793D or compatible chip at 0x4e:0xfff8
>>
>> If no chip at all is found at a given SIO address, it does not make sense
>> to instantiate it. Limit force_id to only work if some chip is found,
>> that is if the chip ID returns a value other than 0xffff.
>
> Agreed, good catch.
>
>>
>> Signed-off-by: Guenter Roeck <linux@roeck-us.net>
>> ---
>>   drivers/hwmon/nct6775.c | 8 ++++----
>>   1 file changed, 4 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/hwmon/nct6775.c b/drivers/hwmon/nct6775.c
>> index d087a8e00cf5..7859a30ce31e 100644
>> --- a/drivers/hwmon/nct6775.c
>> +++ b/drivers/hwmon/nct6775.c
>> @@ -4232,11 +4232,11 @@ static int __init nct6775_find(int sioaddr, struct nct6775_sio_data *sio_data)
>>   	if (err)
>>   		return err;
>>
>> -	if (force_id)
>> +	val = (superio_inb(sioaddr, SIO_REG_DEVID) << 8) |
>> +		superio_inb(sioaddr, SIO_REG_DEVID + 1);
>> +	if (force_id && val != 0xffff)
>>   		val = force_id;
>> -	else
>> -		val = (superio_inb(sioaddr, SIO_REG_DEVID) << 8)
>> -		    | superio_inb(sioaddr, SIO_REG_DEVID + 1);
>> +
>>   	switch (val & SIO_ID_MASK) {
>>   	case SIO_NCT6106_ID:
>>   		sio_data->kind = nct6106;
>
> Reviewed-by: Jean Delvare <jdelvare@suse.de>
>
Thanks!

Guenter