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Date:   Thu, 1 Mar 2018 00:38:16 +0000
From:   "Luis R. Rodriguez" <mcgrof@kernel.org>
To:     Josh Triplett <josh@joshtriplett.org>
Cc:     "Luis R. Rodriguez" <mcgrof@kernel.org>,
        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,
        =?utf-8?B?UmFmYcWCIE1pxYJlY2tp?= <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
Message-ID: <20180301003816.GR14069@wotan.suse.de>
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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.

> 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?

You see other than
CONFIG_FW_LOADER_USER_HELPER
we also have
CONFIG_FW_LOADER_USER_HELPER_FALLBACK
and Android defaults that to y too.

It used to be that CONFIG_FW_LOADER_USER_HELPER_FALLBACK was a mess to
understand in code, and this series has reduced it to simple bool now.

I started wondering if trimming kconfig options may be worth it. Sadly
I don't think we can remove CONFIG_FW_LOADER_USER_HELPER_FALLBACK, and
we'll have to just deal with it mapping to switching a sysctl option.

But I figured it was a good time to also reconsider also if we even had
any need for CONFIG_FW_LOADER_USER_HELPER.

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?

  Luis