From: Arnd Bergmann <arnd@arndb.de>
To: linux-arm-kernel@lists.infradead.org
Cc: Pavel Machek <pavel@ucw.cz>, pali.rohar@gmail.com, sre@debian.org,
        sre@ring0.de, kernel list <linux-kernel@vger.kernel.org>,
        linux-omap@vger.kernel.org, tony@atomide.com, khilman@kernel.org,
        aaro.koskinen@iki.fi, ivo.g.dimitrov.75@gmail.com,
        devicetree@vger.kernel.org, robh+dt@kernel.org, pawel.moll@arm.com,
        mark.rutland@arm.com, ijc+devicetree@hellion.org.uk,
        galak@codeaurora.org
Subject: Re: BCM2048 bluetooth connected over OMAP serial
Date: Wed, 10 Dec 2014 18:02:42 +0100
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On Wednesday 10 December 2014 17:43:33 Pavel Machek wrote:
> 
> So, there's bluetooth chip that's connected to the SoC by UART and some
> GPIOs. What would be right representation in the device tree?
> Something like this?
> 
>         bluetooth {
>                   compatible = "broadcom,bcm2048";
>                   uart = <&uart2>;
>                   reset-gpios = <&gpio3 27 GPIO_ACTIVE_HIGH>; /* want 91 */
>                   host-wakeup-gpios = <&gpio4 5 GPIO_ACTIVE_HIGH>; /* want 101 */
>                   bluetooth-wakeup-gpios = <&gpio2 5 GPIO_ACTIVE_HIGH>; /* want 37 */
>                   chip-type = >;
>                   bt-sysclk = <2>;
>                   reset-gpio-shared = <0>;
>         };
> 
> Is there some way to prevent OMAP tty driver from binding to the
> device and exporting the device to userspace?

I think from the driver perspective, you want this to be a tty line
discipline rather than a driver that attaches to the physical
uart.

For the DT representation, I fear we haven't got a precedent. A uart
phandle sounds reasonable, but there might be other ways to do it
and we should consider if there are better alternatives. It could
possibly be a child node of the uart, but that would require other
infrastructure in the kernel because we don't currently create
devices for those.

	Arnd
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