linux-kernel - Re: [PATCH 10/13] tty: serial: omap: remove some dead code

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Message-ID: <20140424114115.51ab3f98@notabene.brown>
Date:	Thu, 24 Apr 2014 11:41:15 +1000
From:	NeilBrown <neilb@...e.de>
To:	<balbi@...com>
Cc:	Nishanth Menon <nm@...com>, Greg KH <gregkh@...uxfoundation.org>,
	<marcel@...tmann.org>, <gustavo@...ovan.org>,
	<johan.hedberg@...il.com>, <jslaby@...e.cz>,
	<grant.likely@...aro.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	<linux-bluetooth@...r.kernel.org>, <linux-serial@...r.kernel.org>,
	<devicetree@...r.kernel.org>,
	Linux OMAP Mailing List <linux-omap@...r.kernel.org>,
	Tony Lindgren <tony@...mide.com>
Subject: Re: [PATCH 10/13] tty: serial: omap: remove some dead code

On Wed, 23 Apr 2014 20:21:00 -0500 Felipe Balbi <balbi@...com> wrote:

> I have no problem either way, just that unused code doesn't have to be
> sitting in the tree and I'm not entirely sure this GPIO should be
> handled by omap-serial.c, perhaps something more generic inside
> serial-core so other UART drivers can benefit from it.

Perhaps.  But there there are more people I need to convince :-)

> 
> > On the other hand, if you can point out to me what I'm missing, and how I can
> > solve my problem with any virtual GPIOs, I'm all ears.
> > 
> > To make my problem simple and explicit:  I have a device attached to a UART
> > which has a separate regulator.  The regulator should be powered on if and
> 
> So you're using DTR to power the GPIO and hoping that the regulator
> stabilizes quickly enough so that by the time your open() finishes you
> don't have to add nonsensical msleep() calls before writing to the
> device. Sounds a bit fragile to me.

The gpio_set call is synchronous, and the gpio-regulator driver could add a
delay (I think).


> 
> > only if the /dev/ttyXX interface to the UART is open.  The device is a
> > bluetooth transceiver.
> 
> considering this is a BTUART device, why didn't you do this at the ldisc
> level ? hci_uart_open() sounds like a good choice from a quick thinking.
> 

I'll have a look into that, thanks.

NeilBrown


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