linux-kernel - Re: [PATCH] irqchip: bcm2835: Add FIQ support

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Message-ID: <87si6e9p46.fsf@eliezer.anholt.net>
Date:	Wed, 16 Sep 2015 14:48:57 -0400
From:	Eric Anholt <eric@...olt.net>
To:	Russell King - ARM Linux <linux@....linux.org.uk>
Cc:	Noralf Trønnes <noralf@...nnes.org>,
	tglx@...utronix.de, jason@...edaemon.net,
	linux-rpi-kernel@...ts.infradead.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] irqchip: bcm2835: Add FIQ support

Russell King - ARM Linux <linux@....linux.org.uk> writes:

> On Wed, Sep 16, 2015 at 10:02:32AM -0400, Eric Anholt wrote:
>> Russell King - ARM Linux <linux@....linux.org.uk> writes:
>> 
>> > On Mon, Sep 14, 2015 at 07:33:09AM -0700, Eric Anholt wrote:
>> >> So, while FIQ isn't used in upstream, I think it's worthwhile to merge.
>> >> It is another step to bringing the downstream developers into the fold.
>> >
>> > I want to see the code _first_.  Until then, I'm sorry, this patch can't
>> > go in.
>> 
>> If you just want to see "Yes, GPL-compatible code using this is
>> available", then that is:
>
> It's got nothing to do with "GPL-compatible code".  I want to audit
> _all_ code that makes use of FIQ.  It disgusts me that you're trying
> to dress this up as a licensing issue.  It isn't.
>
>> https://github.com/raspberrypi/linux/blob/rpi-4.1.y/drivers/usb/host/dwc_otg/dwc_otg_fiq_stub.S
>> https://github.com/raspberrypi/linux/blob/rpi-4.1.y/drivers/usb/host/dwc_otg/dwc_otg_fiq_fsm.c
>> 
>> If not, I'm curious what exactly is the reason the patch can't go in.
>
> In any case, I'm not going to say yes to code which provides a new
> internal kernel facility for mainline kernels, but with no mainline
> kernel users.  Such code can only be to make external tree maintanence
> easlier, but it has the unintended effect of making mainline kernel
> maintanence harder.
>
> Such facilities _should_ always come with a user of that new facility.
>
> It's nothing personal, it's sane policy from experience.  I've had stuff
> like this in the past, where people have sent new facilities without any
> users, years have gone by without that facility being used.  The facility
> has eventually been removed from the mainline kernel _because_ it doesn't
> have any users.
>
> Moreover, there are people who audit the kernel looking for facilities
> which have no users and propose patches to remove them.
>
> So, if you want some new facility to be merged into mainline kernels,
> and for it to remain in the kernel, always accompany it with a user.

Thanks, this was all I needed.  In the subsystem I work in, the rule has
been "You need to have open userspace using the thing that you can
show", but obviously you only get to merge the user once the core stuff
is done.

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