Re: [PATCH v2 11/11] test_firmware: test three firmware kernel configs using a proc knob

From: Josh Triplett <josh@joshtriplett.org>
To: "Luis R. Rodriguez" <mcgrof@kernel.org>
Cc: "Kees Cook" <keescook@chromium.org>,
	"Greg KH" <gregkh@linuxfoundation.org>,
	"Andrew Morton" <akpm@linux-foundation.org>,
	"Shuah Khan" <shuah@kernel.org>,
	"Martin Fuzzey" <mfuzzey@parkeon.com>,
	"Mimi Zohar" <zohar@linux.vnet.ibm.com>,
	"David Howells" <dhowells@redhat.com>,
	pali.rohar@gmail.com, "Takashi Iwai" <tiwai@suse.de>,
	arend.vanspriel@broadcom.com, "Rafał Miłecki" <zajec5@gmail.com>,
	nbroeking@me.com, "Vikram Mulukutla" <markivx@codeaurora.org>,
	stephen.boyd@linaro.org, "Mark Brown" <broonie@kernel.org>,
	"Dmitry Torokhov" <dmitry.torokhov@gmail.com>,
	"David Woodhouse" <dwmw2@infradead.org>,
	"Linus Torvalds" <torvalds@linux-foundation.org>,
	Abhay_Salunke@dell.com, bjorn.andersson@linaro.org,
	jewalt@lgsinnovations.com, LKML <linux-kernel@vger.kernel.org>,
	"linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>
Subject: Re: [PATCH v2 11/11] test_firmware: test three firmware kernel configs using a proc knob
Date: Wed, 28 Feb 2018 18:25:16 -0800	[thread overview]
Message-ID: <20180301021956.GA12202@localhost> (raw)
In-Reply-To: <20180301003816.GR14069@wotan.suse.de>

On Thu, Mar 01, 2018 at 12:38:16AM +0000, Luis R. Rodriguez wrote:
> On Wed, Feb 28, 2018 at 04:00:58PM -0800, Josh Triplett wrote:
> > On Wed, Feb 28, 2018 at 06:26:03PM +0000, Luis R. Rodriguez wrote:
> > > So for folks who enable CONFIG_FW_LOADER=y, they'd now be forced to gain an
> > > extra 13436 bytes broken down as follows:
> > 
> > Ah, I see.
> > 
> > If you have CONFIG_FW_LOADER and not CONFIG_FW_LOADER_USER_HELPER, then
> > you only have the in-kernel firmware loading mechanism?
> 
> Right, we don't have the old fallback mechanism (which BTW used to be
> the default way back in the hayday).
> 
> > Given the
> > *substantial* size difference between the two, it seems useful to have
> > that option.
> 
> That's what I wanted to get to, is 13436 bytes is*substantial* enough to
> merit a kernel configuration option? It seems like that is the case.

By at least an order of magnitude, yes.

> > What would it gain to combine the two?
> 
> Well Android enables CONFIG_FW_LOADER_USER_HELPER, and if they do, I was trying
> to think if there really was any point in having CONFIG_FW_LOADER_USER_HELPER
> as an option. Who would enable CONFIG_FW_LOADER but not
> CONFIG_FW_LOADER_USER_HELPER?

An embedded system with a fixed set of hardware that needs exclusively a
fixed set of firmware files known at system build time.

> The less hairball of mess of kconfig options the better to test. Even
> though this series has reduced being able to consolidating being
> able to make a kernel now which lets us test all configurations in
> one build.
> 
> Who would save some 13436 bytes in the real world?

*raises hand*