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

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Message-ID: <Ypsgtyyd0LsgIHGp@kroah.com>
Date:   Sat, 4 Jun 2022 11:07:03 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Takashi Iwai <tiwai@...e.de>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        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, Jun 04, 2022 at 08:32:29AM +0200, Takashi Iwai wrote:
> 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!

Sorry about that, I missed it too as I just selected that option to
ensure it built and worked properly on my systems :(

greg k-h