linux-kernel - Re: [PATCH 1/7] platform_device: better support builtin boilerplate avoidance

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Message-ID: <CACRpkdb8GFyPpyAfs67Shac3zVAcaoOTbTHquwG0TpfcjJAt+A@mail.gmail.com>
Date:	Tue, 2 Jun 2015 11:19:37 +0200
From:	Linus Walleij <linus.walleij@...aro.org>
To:	Paul Gortmaker <paul.gortmaker@...driver.com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH 1/7] platform_device: better support builtin boilerplate avoidance

On Thu, May 28, 2015 at 2:50 AM, Paul Gortmaker
<paul.gortmaker@...driver.com> wrote:
> [Re: [PATCH 1/7] platform_device: better support builtin boilerplate avoidance] On 12/05/2015 (Tue 13:46) Linus Walleij wrote:
>
>> This does not inhibit probe() and remove() to be
>> triggered from sysfs does it?
>>
>> What is needed on builtin drivers is to set
>> .suppress_bind_attrs = true on the struct device_driver
>> so that we inhibit the creation of sysfs files to probe
>> and remove the driver by operator intervention.
>
> Is this needed?  I think we will break existing use cases if we do this.
>
> For example, I have IGB as built-in, but I can still unbind one of the
> four devices and make it available for PCI pass through to KVM with:
>
> echo "0000:0a:00.1" > /sys/bus/pci/drivers/igb/unbind
> echo "0000:0a:00.1" > /sys/bus/pci/drivers/pci-stub/bind

Aha PCI device which noone else is dependent on, I guess
it's true.

I think we have a problem as to what "builtin" really means.
For example if this is a builtin regulator, clock, GPIO, DMA etc
driver, we want to suppress the binding/unbinding from userspace
too, since these drivers provide resources to others and
if you unbind them, nasty things happen. Unbinding/rebinding
is fine as long as noone else depend on you. However for
a large number of builtins, that is the case :P

Yours,
Linus Walleij
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