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

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Date:	Mon, 27 Jun 2016 12:09:15 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	Michal Suchanek <hramrach@...il.com>
Cc:	Mark Brown <broonie@...nel.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 Mailing List <linux-kernel@...r.kernel.org>,
	linux-spi <linux-spi@...r.kernel.org>
Subject: Re: [PATCH 3/3] drivers core: allow id match override when manually
 binding driver

On Sun, Jun 26, 2016 at 09:07:08PM +0200, Michal Suchanek wrote:
> On 26 June 2016 at 20:28, Greg Kroah-Hartman <gregkh@...uxfoundation.org> wrote:
> > 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.
> >>
> >> Note that any slave driver that requires configuration will fail to
> >> probe anyway. Only a driver that binds to anything can be bound
> >> successfully.
> >>
> >> Signed-off-by: Michal Suchanek <hramrach@...il.com>
> >> ---
> >>  drivers/base/Kconfig.debug | 14 +++++++++
> >>  drivers/base/bus.c         | 72 +++++++++++++++++++++++++++++++++++++++++++++-
> >>  lib/Kconfig.debug          |  2 ++
> >>  3 files changed, 87 insertions(+), 1 deletion(-)
> >>  create mode 100644 drivers/base/Kconfig.debug
> >>
> >> diff --git a/drivers/base/Kconfig.debug b/drivers/base/Kconfig.debug
> >> new file mode 100644
> >> index 0000000..e21d3cc
> >> --- /dev/null
> >> +++ b/drivers/base/Kconfig.debug
> >> @@ -0,0 +1,14 @@
> >> +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.
> >
> > Ick, no no no.  Why would you ever want to let this happen?  If you
> > really want to override the check, just write things to the 'bind' file
> > in sysfs, that will skip the driver id check entirely, right?
> 
> Well, it does not. Hence this patch which enables skipping the check.
> It's the whole point of it.

Then write the id you wish to use for that driver to the new_id file for
that driver.  Doesn't that work?

thanks,

greg k-h