Re: [RFC 0/3] drivers/hwmon/pmbus: Use STATUS_WORD and add status sensors

[Eddie James <eajames@linux.vnet.ibm.com>]

On 08/07/2017 11:00 PM, Guenter Roeck wrote:
> On 08/07/2017 08:25 PM, Eddie James wrote:
>> From: "Edward A. James" <eajames@us.ibm.com>
>>
>> Hi Guenter,
>>
>> I'm looking for some feedback for some extensions to the pmbus core. 
>> We're
>> looking for some additional functionality, particularly with 
>> STATUS_WORD and
>> obtaining raw status data.
>>
>> The first two patches enable the use of the STATUS_WORD register in 
>> the pmbus
>> core. This allows the use of more default alarm/fault attributes for 
>> default
>> pmbus sensors by allowing the use of the higher byte status bits.
>>
>> The third patch adds "status" attributes to each class of hwmon 
>> sensor created
>> by pmbus. For example, in1_status and temp1_status. These will 
>> display the
>> associated raw status register (e.g. STATUS_INPUT and 
>> STATUS_TEMPERATURE). I
>> realize this is not really "normal" for hwmon or pmbus. These are 
>> potentially
>> very useful in hardware diagnostic situations where it might be 
>> impossible
>> to tell the origin of a failure from a simple alarm or fault bit set. 
>> We really
>> want to access the status registers, and for a multi-page pmbus 
>> device, this is
>> pretty tricky from userspace.
>>
>> Please let me know your thoughts,
>> Thanks,
>
> I don't mind providing such data with debugfs, for example, but I 
> don't see
> the point in providing it as part of the ABI. Which, in part, since it 
> requires
> a lot of thought on my side, is part of the reason why I didn't provide
> feedback to your earlier patches yet. Sorry, I've been exceptionally busy
> lately, and non-standard requests tend to end up at the end of the 
> queue :-(.

No problem! Thanks for the quick response on this.

>
> Any reason why debugfs is not sufficient and/or acceptable for your 
> use case ?
> You _are_ talking about diagnostic situations, which seems to be an 
> exact fit
> for debugfs.

Agreed, great idea, I think debugfs will work perfectly. I probably 
should have thought of that sooner...

How about the first two patches in the series? They are unrelated to 
adding any attributes. Mainly I would
like to have the PB_STATUS_INPUT bit available to trigger the default 
boolean alarm attribute, as our hardware doesn't support any limits.

Thanks again,
Eddie

>
> Guenter
>
>>
>> Edward A. James (3):
>>    drivers/hwmon/pmbus: Access word data for STATUS_WORD and use it by
>>      default
>>    drivers/hmwon/pmbus: store STATUS_WORD in status registers
>>    drivers/hwmon/pmbus: Add sensor status to pmbus attributes
>>
>>   drivers/hwmon/pmbus/pmbus_core.c | 153 
>> +++++++++++++++++++++++++++++++++------
>>   1 file changed, 130 insertions(+), 23 deletions(-)
>>
>