linux-kernel - Re: [PATCH 01/18] staging: typec: tcpm: Add get_usb2_current_limit tcpc

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Message-ID: <5c9f12b9-f121-d33d-33eb-922e9ddbd43c@redhat.com>
Date:   Sun, 6 Aug 2017 16:29:07 +0200
From:   Hans de Goede <hdegoede@...hat.com>
To:     Guenter Roeck <linux@...ck-us.net>,
        Darren Hart <dvhart@...radead.org>,
        Andy Shevchenko <andy@...radead.org>,
        Wolfram Sang <wsa@...-dreams.de>,
        Sebastian Reichel <sre@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>
Cc:     platform-driver-x86@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-i2c@...r.kernel.org, Liam Breck <liam@...workimprov.net>,
        Tony Lindgren <tony@...mide.com>, linux-pm@...r.kernel.org,
        devel@...verdev.osuosl.org
Subject: Re: [PATCH 01/18] staging: typec: tcpm: Add get_usb2_current_limit
 tcpc_dev callback

Hi,

On 06-08-17 16:18, Guenter Roeck wrote:
> On 08/06/2017 05:35 AM, Hans de Goede wrote:
>> A Rp signalling the default current limit indicates that we're possibly
>> connected to an USB2 power-source. In some cases the type-c
>> port-controller may provide the capability to detect the current-limit
>> for USB2 power-sources (through e.g. BC1.2 detection).
>>
>> This commit adds an optional get_usb2_current_limit tcpc_dev callback
>> which allows the port-controller to return the detected current-limit
>> if the CC pin is pulled up with Rp.
>>
>> Signed-off-by: Hans de Goede <hdegoede@...hat.com>
>> ---
>>   drivers/staging/typec/tcpm.c | 5 ++++-
>>   drivers/staging/typec/tcpm.h | 1 +
>>   2 files changed, 5 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/staging/typec/tcpm.c b/drivers/staging/typec/tcpm.c
>> index 20eb4ebcf8c3..9f5adace4309 100644
>> --- a/drivers/staging/typec/tcpm.c
>> +++ b/drivers/staging/typec/tcpm.c
>> @@ -660,7 +660,10 @@ static u32 tcpm_get_current_limit(struct tcpm_port *port)
>>           break;
>>       case TYPEC_CC_RP_DEF:
>>       default:
>> -        limit = 0;
>> +        if (port->tcpc->get_usb2_current_limit)
> 
> I think this callback should just be get_current_limit.

This is only used in the Rp-def case, which usually indicates being connected
with an A->C cable to a USB-2 device and the intend is for the callback to
implement some USB-2 specific method to detect the supported current-limit,
hence the name. If you prefer to name it just get_current_limit I can
change it for v2, but IMHO the usb2 part of the name is important as this
will not get called when USB-PD negotiation is used, nor when Rp has the Rp15
or Rp30 values.

Regards,

Hans



> 
>> +            limit = port->tcpc->get_usb2_current_limit(port->tcpc);
>> +        else
>> +            limit = 0;
>>           break;
>>       }
>> diff --git a/drivers/staging/typec/tcpm.h b/drivers/staging/typec/tcpm.h
>> index 19c307d31a5a..01b7d89379a3 100644
>> --- a/drivers/staging/typec/tcpm.h
>> +++ b/drivers/staging/typec/tcpm.h
>> @@ -108,6 +108,7 @@ struct tcpc_dev {
>>       int (*init)(struct tcpc_dev *dev);
>>       int (*get_vbus)(struct tcpc_dev *dev);
>> +    int (*get_usb2_current_limit)(struct tcpc_dev *dev); /* Optional */
>>       int (*set_cc)(struct tcpc_dev *dev, enum typec_cc_status cc);
>>       int (*get_cc)(struct tcpc_dev *dev, enum typec_cc_status *cc1,
>>                 enum typec_cc_status *cc2);
>>
>