From: Heikki Krogerus <heikki.krogerus@linux.intel.com>
To: Badhri Jagan Sridharan <badhri@google.com>,
Oliver Neukum <oneukum@suse.com>
Cc: Guenter Roeck <linux@roeck-us.net>,
Mats Karrman <mats.dev.list@gmail.com>,
Greg KH <gregkh@linuxfoundation.org>,
Felipe Balbi <felipe.balbi@linux.intel.com>,
LKML <linux-kernel@vger.kernel.org>,
USB <linux-usb@vger.kernel.org>
Subject: Re: [PATCH v17 2/3] usb: USB Type-C connector class
Date: Wed, 19 Apr 2017 14:23:23 +0300 [thread overview]
Message-ID: <20170419112323.GD24062@kuha.fi.intel.com> (raw)
In-Reply-To: <CAPTae5+O83bJm6KL2zWNhYv-SiZ2E490CLt02BbK4hG1xKXraw@mail.gmail.com>
Hi,
On Tue, Apr 18, 2017 at 11:52:33AM -0700, Badhri Jagan Sridharan wrote:
> Hi Heikki,
>
> I have a question regarding the preferred_role node.
>
> +What: /sys/class/typec/<port>/preferred_role
> +Date: March 2017
> +Contact: Heikki Krogerus <heikki.krogerus@linux.intel.com>
> +Description:
> + The user space can notify the driver about the preferred role.
> + It should be handled as enabling of Try.SRC or Try.SNK, as
> + defined in USB Type-C specification, in the port drivers. By
> + default the preferred role should come from the platform.
> +
> + Valid values: source, sink, none (to remove preference)
>
> What is the expected behavior when the userspace changes the
> preferred_role node when the port is in connected state ?
>
> 1. the state machine re-resolves the port roles right away based on
> the new state machine in place ? (or)
No! There are separate attributes for sending role swap requests.
The attribute will "enable" Try.SRC/SNK states, i.e. next time the
state machine is executed, those states need to be considered.
Changing the value of this attribute must not affect the current
connection.
> 2. Wait till the subsequent connect for resolving port roles based on the
> new state machine.
Yes.
> For #1 to happen the policy_engine layer would have to reset the port
> to resolve the port roles based on the (Try.SRC /Try.SNK/ Default)
> new state machine preference.
>
> Say for example when two non-PD devices following none (default state
> machine) are connected, the port role resolution is going to be random.
> But, if the userspace in one of the devices later changes the
> preferred_role to source, then that device is most likely to become source
> if the Try.SRC state-machine is re-run.
>
> Does the above question fall under a policy decision ? If so, should there
> be another node to say if the port roles have to re-resolved based on the
> new state machine right away ?
I don't think we should even consider option #1, but just to be sure,
Oliver, what do you say?
I guess we need to say in the documentation explicitly that changing
the value will not affect the current connection.
Thanks,
--
heikki
next prev parent reply other threads:[~2017-04-19 11:25 UTC|newest]
Thread overview: 64+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-02-21 14:24 [PATCH v17 0/3] USB Type-C Connector class Heikki Krogerus
2017-02-21 14:24 ` [PATCH v17 1/3] lib/string: add sysfs_match_string helper Heikki Krogerus
2017-02-21 14:24 ` [PATCH v17 2/3] usb: USB Type-C connector class Heikki Krogerus
2017-03-02 15:22 ` Mats Karrman
2017-03-03 3:13 ` Guenter Roeck
2017-03-03 7:29 ` Mats Karrman
2017-03-03 9:48 ` Enric Balletbo Serra
2017-03-03 12:59 ` Heikki Krogerus
2017-03-03 14:49 ` Guenter Roeck
2017-03-03 19:27 ` Mats Karrman
2017-03-06 9:37 ` Oliver Neukum
2017-03-06 13:14 ` Heikki Krogerus
2017-03-07 22:30 ` Mats Karrman
2017-03-08 1:38 ` Guenter Roeck
2017-04-08 23:09 ` USB Type-C Port Manager API concern Mats Karrman
2017-04-09 15:16 ` Guenter Roeck
2017-04-09 21:05 ` Mats Karrman
2017-04-14 2:57 ` Guenter Roeck
2017-04-14 8:30 ` Mats Karrman
2017-03-08 13:58 ` [PATCH v17 2/3] usb: USB Type-C connector class Heikki Krogerus
2017-03-10 22:22 ` Mats Karrman
2017-03-10 23:41 ` Guenter Roeck
2017-04-18 18:52 ` Badhri Jagan Sridharan
2017-04-19 11:23 ` Heikki Krogerus [this message]
2017-04-19 14:45 ` Badhri Jagan Sridharan
2017-04-19 15:14 ` Guenter Roeck
2017-04-19 17:22 ` Badhri Jagan Sridharan
2017-04-19 19:29 ` Guenter Roeck
2017-04-20 12:24 ` Heikki Krogerus
2017-04-20 19:46 ` Badhri Jagan Sridharan
2017-04-21 12:12 ` Heikki Krogerus
2017-04-21 13:14 ` Guenter Roeck
2017-04-21 14:27 ` Rajaram R
2017-04-21 16:43 ` Guenter Roeck
2017-04-22 9:23 ` Rajaram R
2017-04-24 17:50 ` Badhri Jagan Sridharan
2017-04-25 8:26 ` Rajaram R
2017-04-25 14:10 ` Guenter Roeck
2017-04-27 6:20 ` Rajaram R
2017-04-27 18:10 ` Guenter Roeck
2017-04-28 10:52 ` Heikki Krogerus
2017-04-20 11:55 ` Heikki Krogerus
2017-03-03 14:41 ` Guenter Roeck
2017-03-03 3:35 ` Peter Chen
2017-03-03 4:29 ` Guenter Roeck
2017-03-03 4:52 ` Peter Chen
2017-03-03 14:36 ` Guenter Roeck
2017-03-06 1:24 ` Peter Chen
2017-03-03 14:31 ` Heikki Krogerus
2017-03-06 1:15 ` Peter Chen
2017-03-06 13:16 ` Heikki Krogerus
2017-03-07 1:36 ` Peter Chen
2017-03-07 8:57 ` Heikki Krogerus
2017-03-08 1:53 ` Guenter Roeck
2017-03-08 6:50 ` Peter Chen
2017-03-08 14:44 ` Guenter Roeck
2017-03-09 2:00 ` Peter Chen
2017-02-21 14:24 ` [PATCH v17 3/3] usb: typec: add driver for Intel Whiskey Cove PMIC USB Type-C PHY Heikki Krogerus
2017-02-21 15:42 ` [PATCH v17 0/3] USB Type-C Connector class Felipe Balbi
2017-03-21 11:14 ` Heikki Krogerus
2017-03-21 10:23 ` Greg KH
2017-03-21 10:37 ` Heikki Krogerus
2017-03-22 21:15 ` Mats Karrman
2017-03-23 8:16 ` Heikki Krogerus
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