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Date: Fri, 19 Aug 2016 16:44:29 +0200
From: Sebastian Reichel <sre@kernel.org>
To: One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk>
Cc: Rob Herring <robh@kernel.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Marcel Holtmann <marcel@holtmann.org>, Jiri Slaby <jslaby@suse.com>,
	Pavel Machek <pavel@ucw.cz>,
	Peter Hurley <peter@hurleysoftware.com>,
	NeilBrown <neil@brown.name>,
	"Dr . H . Nikolaus Schaller" <hns@goldelico.com>,
	Arnd Bergmann <arnd@arndb.de>,
	Linus Walleij <linus.walleij@linaro.org>,
	"open list:BLUETOOTH DRIVERS" <linux-bluetooth@vger.kernel.org>,
	"linux-serial@vger.kernel.org" <linux-serial@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [RFC PATCH 0/3] UART slave device bus
Message-ID: <20160819144428.akddnwfl5g5qhtq3@earth>
References: <20160818011445.22726-1-robh@kernel.org>
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Hi Alan,

On Fri, Aug 19, 2016 at 12:03:05PM +0100, One Thousand Gnomes wrote:
> > I meant "Either some function similar to userspace's poll() is
> > needed, ...". Something like uart_dev_wait_for_rx()
>=20
> You can't really do that - it might never return and then how do
> you want to handle timeouts and cleanups

Well there could be some timeout. As I said, I was thinking about
an API similar to poll(), but I agree, that a callback based API
is probably the better solution. It's simpler to implement and in
most cases simpler to use.

> > Alternatively the rx function could be a callback, that
> > is called when there is new data.
>=20
> That's what the existing API gives you as an ldisc, it can't be
> immediate in many cases however but must be buffered.

I know and I think the ldisc API is fine in this regard. Also
the buffering allows DMA, so that's obviously preferred.

> > > I'm assuming the only immediate consumers are in-kernel. =20
> >=20
> > Yes, but the driver should be notified about incoming data.

-- Sebastian

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