linux-kernel - Re: [PATCH] spi/pl022: Devicetree support w/o platform data

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Date:	Tue, 18 Sep 2012 13:13:30 +0000
From:	Arnd Bergmann <arnd@...db.de>
To:	Roland Stigge <stigge@...com.de>
Cc:	broonie@...nsource.wolfsonmicro.com, grant.likely@...retlab.ca,
	linus.walleij@...aro.org, lee.jones@...aro.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	STEricsson_nomadik_linux@...t.st.com,
	devicetree-discuss@...ts.ozlabs.org, aletes.xgr@...il.com,
	kevin.wells@....com, srinivas.bakki@....com
Subject: Re: [PATCH] spi/pl022: Devicetree support w/o platform data

On Tuesday 18 September 2012, Roland Stigge wrote:
> --- linux-2.6.orig/Documentation/devicetree/bindings/spi/spi_pl022.txt
> +++ linux-2.6/Documentation/devicetree/bindings/spi/spi_pl022.txt
> @@ -10,6 +10,15 @@ Optional properties:
>  - cs-gpios : should specify GPIOs used for chipselects.
>    The gpios will be referred to as reg = <index> in the SPI child nodes.
>    If unspecified, a single SPI device without a chip select can be used.
> +- pl022,bus-id : Bus ID (0, 1, ...)

I don't understand why we need the bus-id here. My understanding is that
this is a linux-specific number that should not be necessary when all
devices are described in the device tree rather than through spi_board_info.

Can't you just set master->bus_num to -1 when using the DT for probing?

> +- pl022,enable-dma : enables DMA driven transfers (boolean)

Similar thing here: Can't you just set the enable_dma flag when
a dma channel is provided in the device tree and unset it otherwise?

It also seems a bit pointless to enable DMA mode when you don't provide
a way to specify the channel at the same time.

	Arnd
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