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

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Message-ID: <20161116093035.GA30235@kuha.fi.intel.com>
Date:   Wed, 16 Nov 2016 11:30:35 +0200
From:   Heikki Krogerus <heikki.krogerus@...ux.intel.com>
To:     Badhri Jagan Sridharan <badhri@...gle.com>,
        Greg KH <gregkh@...uxfoundation.org>
Cc:     Guenter Roeck <linux@...ck-us.net>,
        Oliver Neukum <oneukum@...e.com>,
        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 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.


Thanks,

-- 
heikki