linux-kernel - Re: [PATCH 3/3] drivers core: allow id match override when manually binding driver

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Date:	Sun, 26 Jun 2016 02:17:37 +0100
From:	Mark Brown <broonie@...nel.org>
To:	Michal Suchanek <hramrach@...il.com>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Ingo Molnar <mingo@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Kees Cook <keescook@...omium.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Dan Williams <dan.j.williams@...el.com>,
	Tejun Heo <tj@...nel.org>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Davidlohr Bueso <dave@...olabs.net>,
	Andrey Ryabinin <aryabinin@...tuozzo.com>,
	Nikolay Aleksandrov <nikolay@...ulusnetworks.com>,
	Dmitry Vyukov <dvyukov@...gle.com>,
	Adrien Schildknecht <adrien+dev@...ischi.me>,
	linux-kernel@...r.kernel.org, linux-spi@...r.kernel.org
Subject: Re: [PATCH 3/3] drivers core: allow id match override when manually
 binding driver

On Thu, Jun 23, 2016 at 05:41:20PM -0000, Michal Suchanek wrote:

> This allows binding spidev on any slave device by hand using sysfs
> without adding superfluous compatibles or any other needless
> complication.

This says "spidev" but it's a change to the driver core, not something
that is specific to spidev.  It needs to be explained in terms ofn the
driver core, especially given that other runtime ID setting is done in a
particular bus.

> +menuconfig DRIVER_MATCH_OVERRIDE
> +	bool "Allow manual driver binding to override id match (DANGEROUS)"
> +	default n
> +	help
> +	  When binding a driver manually bypass the check of driver id table
> +	  against device id in driver core. This can be useful for development
> +	  or on buses that don't provide reliable device identification.
> +
> +config DRIVER_MATCH_OVERRIDE_BUSES
> +	string "Specify buses for which id matching will be overridden"
> +	default "spi"
> +	depends on DRIVER_MATCH_OVERRIDE
> +	help
> +	  space separated bus names

This doesn't seem at all idomatic for how I'd expect bus features to be
implemented, or Linux configuration in general.  If we're going to allow
a feature like this at the core level we should just allow it, if we're
going to opt buses into any such feature I'd expect it to be done
unconditionally.

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