linux-kernel - Re: [GIT PULL] Driver core changes for 5.19-rc1

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Date:   Sat, 04 Jun 2022 08:32:29 +0200
From:   Takashi Iwai <tiwai@...e.de>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Greg KH <gregkh@...uxfoundation.org>, Takashi Iwai <tiwai@...e.de>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        Saravana Kannan <saravanak@...gle.com>
Subject: Re: [GIT PULL] Driver core changes for 5.19-rc1

On Sat, 04 Jun 2022 00:23:18 +0200,
Linus Torvalds wrote:
> 
> Augh.
> 
> This was very badly done, and I'm not talking about the deferred probe
> timeout things that caused problems for people.
> 
> On Fri, Jun 3, 2022 at 4:28 AM Greg KH <gregkh@...uxfoundation.org> wrote:
> >
> >         - firmware_loader reorganization and additions including the
> >           ability to have XZ compressed firmware images and the ability
> >           for userspace to initiate the firmware load when it needs to,
> >           instead of being always initiated by the kernel.
> 
> This is actively misleading.
> 
> We *always* supported XZ compressed firmware images, and it was
> enabled by CONFIG_FW_LOADER_COMPRESS,
> 
> What's new is the option to use ZSTD compression.
> 
> However, the Kconfig file addition for this was done as badly as the
> above explanation was, and the FW_LOADER_COMPRESS_XZ option was added
> with a help message and a default value that both are complete
> garbage.
> 
> So when you do "make oldconfig", you would be expected to say 'N', and
> in the process you lose the existing XZ compression.
> 
> Only when the resulting kernel doesn't boot, and you spent half an
> hour trying to bisect things, and you start looking closer, do you
> notice that "ooh, the config changed in bad ways".
> 
> Yeah, I'm a bit grumpy. This was *really* annoying.
> 
> The commit that does this breakage is literally called "firmware: Add
> the support for ZSTD-compressed firmware files", and only when looking
> closer do you notice that IT REMOVES SUPPORT FOR XZ COMPRESSION BY
> DEFAULT.
> 
> Because even when keeping the FW_LOADER_COMPRESS option enabled, the
> XZ compression is just gone, gone, gone, unless you realize that it
> was implicitly enabled before, and now needs that default disable of
> FW_LOADER_COMPRESS_XZ to be enabled.
> 
> I've said this before, and I'll say it here again (and I bet I'll have
> to say it in the future too): the kernel config is probably the most
> annoying part of building a kernel for anybody.
> 
> And it damn well does NOT HELP when people then actively break things,
> and ask actively bad and misleading questions. In this case, for
> example, it's not just that the XZ option is now misleading by
> default, it's also that the whole thing has been set up so that you
> can say "enable compressed images", but then HAVE NO ACTUAL
> COMPRESSION METHOD!
> 
> Grr. This was *REALLY* badly done.

Mea culpa, I hesitated to add "default y", but it should have been
added at least for the case with the config takeover case.  Now I see
that you've already added "default y" to
CONFIG_FW_LOADER_COMPRESS_XZ.  Thanks for taking care of this!


Takashi