linux-kernel - Re: [spi-devel-general] [PATCH 1/2] spi/spi_s3c64xx: Make probe more robust against missing board config

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Message-ID: <20100823095722.GA6061@rakim.wolfsonmicro.main>
Date:	Mon, 23 Aug 2010 10:57:22 +0100
From:	Mark Brown <broonie@...nsource.wolfsonmicro.com>
To:	Jassi Brar <jassisinghbrar@...il.com>
Cc:	David Brownell <dbrownell@...rs.sourceforge.net>,
	Grant Likely <grant.likely@...retlab.ca>,
	spi-devel-general@...ts.sourceforge.net,
	linux-kernel@...r.kernel.org
Subject: Re: [spi-devel-general] [PATCH 1/2] spi/spi_s3c64xx: Make probe
 more robust against missing board config

On Sun, Aug 22, 2010 at 12:37:25PM +0900, Jassi Brar wrote:

> An immediate kernel crash ? :)
> I mean if the developer didn't even run-check the board init code, he ought
> to face a kernel crash.
> On a more lenient note, probably a check like yours or !sci->num_cs
> could be added.

I'd personally not actually be that upset with a BUG_ON(), my main
reason for changing the code was that it was non-obvious what the source
of the error was rather than the fact that things fell over.

> > It did occur to me that a nice way of dealing with this would be to have
> > the driver default to using the built in chip select (even if driven as
> > a GPIO for the sake of code simplicity) but leave the current method
> > there as an override.  That way if people are using the IP block in the
> > "natural" manner they'd have less to set up.

> I thought about it but decided against it, for that would complicate the
> driver by having to switch between two mechanism in runtime and there
> are some peculiarities in the controller about clocking and CS'ing.

Yeah, that's why I suggested driving it as a GPIO for simplicity - from
the user point of view it doesn't matter if that's what the controller
does so long as the driver figures out the chip select without external
help.
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