Re: [PATCH] spi: Force the registration of the spidev devices

From: Alexandre Belloni <alexandre.belloni@free-electrons.com>
To: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Maxime Ripard <maxime.ripard@free-electrons.com>,
	Mark Brown <broonie@kernel.org>,
	linux-spi <linux-spi@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] spi: Force the registration of the spidev devices
Date: Mon, 5 May 2014 15:57:02 +0200	[thread overview]
Message-ID: <20140505135701.GA21940@piout.net> (raw)
In-Reply-To: <CAMuHMdWZ1rvC+tkT=CbfMwZtppyJ_KpzT7JrLd5k5P2oxzA+8g@mail.gmail.com>

On 05/05/2014 at 09:10:43 +0200, Geert Uytterhoeven wrote :
> Hi Maxime,
> 
> On Mon, May 5, 2014 at 6:17 AM, Maxime Ripard
> <maxime.ripard@free-electrons.com> wrote:
> > On Fri, May 02, 2014 at 01:28:26AM +0200, Geert Uytterhoeven wrote:
> >> On Fri, May 2, 2014 at 12:36 AM, Maxime Ripard
> >> <maxime.ripard@free-electrons.com> wrote:
> >> > But it actually doesn't work in a case where you can't really predict
> >> > what is on the other side of the bus. Either because, on the board
> >> > you're using the pins are exposed and it's pretty much up to the user
> >> > to know what to put on it. That could be handled by DT overlays
> >> > though.
> >> >
> >> > What never works is where the device on the other side is so generic
> >> > that you really can't tell what it does. Think of a microcontroller
> >> > that would behave as a SPI slave. It's behaviour and what it does is
> >> > pretty much dependant of what we flashed on it, and suddenly the
> >> > compatible string is not the proper reprensentation anymore.
> >>
> >> So you will (hopefully soon) use overlay DT to change the DTS to match what's
> >> connected?
> >
> > Not really, because you can't declare a spidev device in the DT.
> 
> Yes you can. I've done it before.
> 
> See also "git grep -w spidev -- arch/arm/*/dts/".
> 

I'm pretty sure that doesn't work as there is no compatible matching
"spidev"

My guess would be that you added it in spidev.c

-- 
Alexandre Belloni, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com