From: Arnd Bergmann <arnd@arndb.de>
To: "Reizer, Eyal" <eyalr@ti.com>
Cc: Kalle Valo <kvalo@codeaurora.org>, Eyal Reizer <eyalreizer@gmail.com>,
        "linux-wireless@vger.kernel.org" <linux-wireless@vger.kernel.org>,
        "netdev@vger.kernel.org" <netdev@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
        linux-spi@vger.kernel.org
Subject: Re: [PATCHv2] wlcore: spi: add wl18xx support
Date: Mon, 18 Apr 2016 00:19:41 +0200
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On Sunday 10 April 2016 07:37:23 Reizer, Eyal wrote:
> Add support for using with both wl12xx and wl18xx.
> 
> - all wilink family needs special init command for entering wspi mode.
>   extra clock cycles should be sent after the spi init command while the
>   cs pin is high.
> - switch to controling the cs pin from the spi driver for achieveing the
>   above.
> - the selected cs gpio is read from the spi device-tree node using the
>   cs-gpios field and setup as a gpio.
> - See the example below for specifying the cs gpio using the cs-gpios entry
> &spi0   {
>         ...
>         cs-gpios = <&gpio0 5 0>;
>         ...
>         wlcore: wlcore@0 {
>                 compatible = "ti,wl1835";
>         ...
>         ...
>         };
> };
> 
> Signed-off-by: Eyal Reizer <eyalr@ti.com>

I don't think this can work in general: not all SPI hosts uses GPIOs
for controlling CS, so the logic can't work, and it's also a layering
violation for the driver to look at the parent.

I would suggest fixing this using a new API function from the SPI
core, if we don't already have a generic way to do it.

	Arnd