linux-kernel - Re: [PATHCv10 1/2] usb: USB Type-C connector class

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Date:   Wed, 16 Nov 2016 13:09:10 +0200
From:   Heikki Krogerus <heikki.krogerus@...ux.intel.com>
To:     Greg KH <gregkh@...uxfoundation.org>,
        Badhri Jagan Sridharan <badhri@...gle.com>,
        Guenter Roeck <linux@...ck-us.net>,
        Oliver Neukum <oneukum@...e.com>
Cc:     Felipe Balbi <felipe.balbi@...ux.intel.com>,
        Bin Gao <bin.gao@...ux.intel.com>,
        LKML <linux-kernel@...r.kernel.org>,
        USB <linux-usb@...r.kernel.org>
Subject: Re: [PATHCv10 1/2] usb: USB Type-C connector class

On Wed, Nov 16, 2016 at 10:49:49AM +0100, Greg KH wrote:
> On Wed, Nov 16, 2016 at 11:30:35AM +0200, Heikki Krogerus wrote:
> > On Tue, Nov 15, 2016 at 04:19:10PM -0800, Badhri Jagan Sridharan wrote:
> > > Hi,
> > > 
> > > At present I am using the uevent in the userspace to infer
> > > the Presence of a port on the remote end through the
> > > appearance of usbc*-partner.
> > > 
> > > Userspace uses this info to decide on when to show a USB
> > > notification on the screen and what should be the options
> > > provided in the dialog.
> > > 
> > > I was assuming that this is not something that would be dropped.
> > > 
> > > Coding using events was relatively easier to program from userspace ..
> > > 
> > > Is it possible to use POLL for identifying the appearance of port partner ?
> > > I did not notice sysfs_notify call in typec_connect/typec_disconnect.
> > > 
> > > It would also be nice to have uevent notifications when the contents
> > > of current_data_role or current_power_role changes.
> > > 
> > > Is that too costly to have ?
> > 
> > Greg, could you give your opinion. In this case we do have attribute
> > files that the user space can poll. Data role is the USB data role, so
> > host or device, and it can change for example if the partner executes
> > a swap. The same can happen with the power role.
> 
> So the same 'struct device' switches roles and attribute files are
> updated that need to be re-read?  If so, yes KOBJ_CHANGE is correct, if
> a struct device is added/removed for this, then no, it doesn't make
> sense.

OK, I'll add KOBJ_CHANGE for those.

So is it OK to everybody if I remove the KOBJ_CHANGE in
typec_connect()? We will see uevent KOBJ_ADD since the partner (or
cable) is added in any case. Badhri, Oliver?


Thanks,

-- 
heikki