linux-kernel - Re: [RFC PATCHv2] usb: USB Type-C Connector Class

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Message-ID: <20160530131951.GA13055@kuha.fi.intel.com>
Date:	Mon, 30 May 2016 16:19:51 +0300
From:	Heikki Krogerus <heikki.krogerus@...ux.intel.com>
To:	Guenter Roeck <linux@...ck-us.net>,
	Oliver Neukum <oneukum@...e.com>
Cc:	Greg KH <gregkh@...uxfoundation.org>,
	Mathias Nyman <mathias.nyman@...ux.intel.com>,
	Felipe Balbi <felipe.balbi@...ux.intel.com>,
	Rajaram R <rajaram.officemail@...il.com>,
	Andy Shevchenko <andy.shevchenko@...il.com>,
	linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org
Subject: Re: [RFC PATCHv2] usb: USB Type-C Connector Class

Hi guys,

I'm attaching a diff instead of full v3. I'm not yet adding attributes
for the reset and cable_reset. I still don't understand what is the
case where the userspace would need to be able to tricker reset? Why
isn't it enough for the userspace to be able to enter/exit modes?
Oliver! Can you please comment?

Guenter, I removed the driver_data you proposed and changed the API
so that the struct typec_capability is passed to the function pointers
instead of struct typec_port. The driver_data pointer felt a bit
clumsy to me, as it was something extra that always had to be passed
to every function. Let me know if it's not OK for you.

I also made a change to the partner devices so that they always have
the port as their parent. That will have an effect on the location
where the partner device is exposed in sysfs (so now always under the
port). And because of that, I would like to get an OK from you guys.

I'm a bit concerned about the current API for adding the alternate
modes. Since we are passing the parent for an alternate mode as
struct device, it makes it possible for the caller to place it into
some wrong place. But I guess we can change the API even later.

We also need to decide how the alternate modes a port support are
exposed to the userspace. Do we just assume the port drivers will
create them as devices under the port device itself, just like
alternate modes of partners and cable plugs are exposed under the
partners and cable plugs? That works for me, but again, the class does
not have any effect on that, and it will be just a guideline. Maybe
we can add some kind of helpers and force the port drivers to use
them.

And finally, mostly as a reminder for myself. I didn't yet add
attributes for Try.SRC/SNK. So can we make it something like
"preferred_role" like I think you proposed Guenter? The
"current_data_role" I'm dropping.

So to summarize. There are still open questions regarding the required
attributes and attribute names and locations. Let's agree on those
quickly and then we can polish the patch.

Thanks,

-- 
heikki

View attachment "typec_update.diff" of type "text/plain" (8139 bytes)