Re: [RFC 2/7] tty: add support for "tty slave" devices

From: Pavel Machek <pavel@ucw.cz>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: "Sebastian Reichel" <sre@kernel.org>,
	"Tony Lindgren" <tony@atomide.com>,
	"Rob Herring" <robh+dt@kernel.org>,
	"Mark Rutland" <mark.rutland@arm.com>,
	"Marcel Holtmann" <marcel@holtmann.org>,
	"Jiri Slaby" <jslaby@suse.com>,
	"Ville Tervo" <ville.tervo@iki.fi>,
	"Filip Matijević" <filip.matijevic.pz@gmail.com>,
	"Aaro Koskinen" <aaro.koskinen@iki.fi>,
	"Pali Rohár" <pali.rohar@gmail.com>,
	ivo.g.dimitrov.75@gmail.com, linux-bluetooth@vger.kernel.org,
	linux-serial@vger.kernel.org, linux-omap@vger.kernel.org,
	devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
	NeilBrown <neilb@suse.de>
Subject: Re: [RFC 2/7] tty: add support for "tty slave" devices
Date: Sun, 14 Aug 2016 10:48:22 +0200	[thread overview]
Message-ID: <20160814084822.GA21321@amd> (raw)
In-Reply-To: <20160813100345.GA14665@kroah.com>

On Sat 2016-08-13 12:03:45, Greg Kroah-Hartman wrote:
> On Sat, Aug 13, 2016 at 05:14:33AM +0200, Sebastian Reichel wrote:
> > From: NeilBrown <neilb@suse.de>
> > 
> > A "tty slave" is a device connected via UART.  It may need a driver to,
> > for example, power the device on when the tty is opened, and power it
> > off when the tty is released.
> > 
> > Signed-off-by: NeilBrown <neilb@suse.de>
> > Signed-off-by: Sebastian Reichel <sre@kernel.org>

Acked-by: Pavel Machek <pavel@ucw.cz>

> > @@ -3317,6 +3318,11 @@ struct device *tty_register_device_attr(struct tty_driver *driver,
> >  	retval = device_register(dev);
> >  	if (retval)
> >  		goto error;
> > +	if (device && device->of_node)
> > +		/* Children are platform devices and will be
> > +		 * runtime_pm managed by this tty.
> > +		 */
> > +		of_platform_populate(device->of_node, NULL, NULL, dev);
> 
> Why are these platform devices?  And why only OF?

OF based systems are the only ones that have this problem, so that's
the only place where we can test this solution.

Given that these devices are connected over the UART, it seems right
to categorize them as platform devices... You can't connect PCI, SATA
or USB device over UART port.

									Pavel
-- 
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