linux-kernel - Re: [PATCH v4 0/7] typec: tcpm: Add sink side support for PPS

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Message-ID: <3611b3dd-2512-441f-9239-17af2dab0929@roeck-us.net>
Date:   Tue, 30 Jan 2018 06:27:44 -0800
From:   Guenter Roeck <linux@...ck-us.net>
To:     Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Adam Thomson <Adam.Thomson.Opensource@...semi.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Sebastian Reichel <sre@...nel.org>,
        Hans de Goede <hdegoede@...hat.com>,
        Yueyao Zhu <yueyao.zhu@...il.com>,
        Rui Miguel Silva <rmfrfs@...il.com>,
        linux-usb@...r.kernel.org, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org, support.opensource@...semi.com
Subject: Re: [PATCH v4 0/7] typec: tcpm: Add sink side support for PPS

On 01/30/2018 05:25 AM, Heikki Krogerus wrote:
> On Tue, Jan 02, 2018 at 03:50:48PM +0000, Adam Thomson wrote:
>> This patch set adds sink side support for the PPS feature introduced in the
>> USB PD 3.0 specification.
>>
>> The source PPS supply is represented using the Power Supply framework to provide
>> access and control APIs for dealing with it's operating voltage and current,
>> and switching between a standard PDO and PPS APDO operation. During standard PDO
>> operation the voltage and current is read-only, but for APDO PPS these are
>> writable as well to allow for control.
>>
>> It should be noted that the keepalive for PPS is not handled within TCPM. The
>> expectation is that the external user will be required to ensure re-requests
>> occur regularly to ensure PPS remains and the source does not hard reset.
> 
> Sorry for the late reply. I don't have any major problems with these
> other than with 6/7. The documentation should be for the psy class,
> not tcpm. I'm also not comfortable with the "select POWER_SUPPLY", but
> if Guenter does not think it's a problem, I'm fine with it. I guess we

"select POWER_SUPPLY" seems to be quite widely used, so I don't have problems
with it as long as it is ok for PS maintainers.

> can always, for example, introduce stubs for the power_supply*
> functions, and drop the dependency later.
> 
That doesn't sound like a good idea unless generic stubs are already available.

> But as usual with tcpm.c, Guenter needs to give his ACK.
> 
I'll try to get to it this week.

Guenter

> Oh yes, and Sebastian needs to ACK the power_supply changes or course.
> 
> 
> Thanks,
>