linux-kernel - Re: [RFC PATCH v2 6/7] typec: tcpm: Represent source supply through power

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Message-ID: <3f1b813d-a9a9-756e-718c-5b2aa2b72906@redhat.com>
Date:   Sat, 25 Nov 2017 15:03:02 +0100
From:   Hans de Goede <hdegoede@...hat.com>
To:     Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Adam Thomson <Adam.Thomson.Opensource@...semi.com>
Cc:     Guenter Roeck <linux@...ck-us.net>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Sebastian Reichel <sre@...nel.org>,
        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: [RFC PATCH v2 6/7] typec: tcpm: Represent source supply through
 power_supply class

Hi,

On 11/24/2017 01:19 PM, Heikki Krogerus wrote:
> Hi,
> 
> On Tue, Nov 14, 2017 at 11:44:47AM +0000, Adam Thomson wrote:
>> diff --git a/drivers/usb/typec/tcpm.c b/drivers/usb/typec/tcpm.c
>> index 78983e1..7c26c3d 100644
>> --- a/drivers/usb/typec/tcpm.c
>> +++ b/drivers/usb/typec/tcpm.c
>> @@ -12,6 +12,7 @@
>>   #include <linux/kernel.h>
>>   #include <linux/module.h>
>>   #include <linux/mutex.h>
>> +#include <linux/power_supply.h>
>>   #include <linux/proc_fs.h>
>>   #include <linux/sched/clock.h>
>>   #include <linux/seq_file.h>
>> @@ -277,6 +278,10 @@ struct tcpm_port {
>>   	u32 current_limit;
>>   	u32 supply_voltage;
>>   
>> +	/* Used to export TA voltage and current */
>> +	struct power_supply *psy;
>> +	struct power_supply_desc psy_desc;
>> +
>>   	u32 bist_request;
>>   
>>   	/* PD state for Vendor Defined Messages */
>> @@ -1756,6 +1761,7 @@ static int tcpm_pd_select_pdo(struct tcpm_port *port)
>>   	int ret = -EINVAL;
>>   
>>   	port->pps_data.supported = false;
>> +	port->psy_desc.type = POWER_SUPPLY_TYPE_USB_PD;
>>   
>>   	/*
>>   	 * Select the source PDO providing the most power while staying within
>> @@ -1775,8 +1781,10 @@ static int tcpm_pd_select_pdo(struct tcpm_port *port)
>>   			mv = pdo_min_voltage(pdo);
>>   			break;
>>   		case PDO_TYPE_APDO:
>> -			if (pdo_apdo_type(pdo) == APDO_TYPE_PPS)
>> +			if (pdo_apdo_type(pdo) == APDO_TYPE_PPS) {
>>   				port->pps_data.supported = true;
>> +				port->psy_desc.type = POWER_SUPPLY_TYPE_USB_PD_PPS;
>> +			}
>>   			continue;
>>   		default:
>>   			tcpm_log(port, "Invalid PDO type, ignoring");
>> @@ -2248,6 +2256,9 @@ static void tcpm_reset_port(struct tcpm_port *port)
>>   	port->try_snk_count = 0;
>>   	port->supply_voltage = 0;
>>   	port->current_limit = 0;
>> +	port->psy_desc.type = POWER_SUPPLY_TYPE_USB_TYPE_C;
> 
> Is it OK to everybody that the type of the psy is changed like that?
> Hans?!
> 
> We do have drivers that already change the type, for example
> drivers/power/supply/isp1704_charger.c, but what does the user space
> expect? The ABI for the power supply class was never documented I
> guess.

The main userspace consumer of the power_supply sysfs class is upower,
upower knows about 3 types: "Mains", "Battery" and "USB", anything
else it gives a type of UP_DEVICE_KIND_UNKNOWN. So POWER_SUPPLY_TYPE_USB_TYPE_C
vs POWER_SUPPLY_TYPE_USB_PD_PPS does matter to it.

Regards,

Hans