linux-kernel - Re: [PATCHv2] wlcore: spi: add wl18xx support

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Date:	Tue, 19 Apr 2016 16:21:35 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	"Reizer, Eyal" <eyalr@...com>
Cc:	Kalle Valo <kvalo@...eaurora.org>,
	Eyal Reizer <eyalreizer@...il.com>,
	"linux-wireless@...r.kernel.org" <linux-wireless@...r.kernel.org>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-spi@...r.kernel.org" <linux-spi@...r.kernel.org>
Subject: Re: [PATCHv2] wlcore: spi: add wl18xx support

On Tuesday 19 April 2016 09:05:45 Reizer, Eyal wrote:
> > > It is also part of the generic spi.h (include/Linux/spi/spi.h),
> > > already part of " struct spi_device" So it seemed redundant adding
> > > another mechanism for implementing the same.
> > > Platform that interact with a wilink need to use it, and platforms
> > > that don't have this capability will probably not interact with a wilink device
> > using SPI.
> > 
> > The cs_gpio field in spi_device belongs to the spi host controller, no other
> > slave driver uses it.
> > 
> > I wasn't asking for a duplication of this mechanism, but an interface to use it
> > properly. Internally, the spi core uses the spi_set_cs() function to pick a CS.
> > Find a way to use that rather than reimplementing it incorrectly.
> > 
> 
> Understood. As this special CS manipulation is unique to wspi (wilink spi)  I think the 
> best option is to move this gpio allocation into wlcore_spi as a new device tree entry
> used only by this driver.
> If you agree I will submit a v3.

I don't think that can work either: aside of not solving the problem
of wilink devices on spi controllers that don't use gpio, it also doesn't
solve the problem of what happens when the driver manually triggers the
gpio to hold the CS signal while another driver talks to a different
device using another CS on the same controller.

	Arnd