Re: [PATCH 04/14] firmware_loader: add built-in firmware kconfig entry
From: Greg KH
Date: Mon Oct 11 2021 - 13:46:17 EST
On Mon, Oct 11, 2021 at 10:35:37AM -0700, Luis Chamberlain wrote:
> On Tue, Oct 05, 2021 at 04:30:06PM +0200, Greg KH wrote:
> > On Fri, Sep 17, 2021 at 11:22:16AM -0700, Luis R. Rodriguez wrote:
> > > From: Luis Chamberlain <mcgrof@xxxxxxxxxx>
> > >
> > > The built-in firmware is always supported when a user enables
> > > FW_LOADER=y today, that is, it is built-in to the kernel. When the
> > > firmware loader is built as a module, support for built-in firmware
> > > is skipped. This requirement is not really clear to users or even
> > > developers.
> > >
> > > Also, by default the EXTRA_FIRMWARE is always set to an empty string
> > > and so by default we really have nothing built-in to that kernel's
> > > sections for built-in firmware, so today a all FW_LOADER=y kernels
> > > spins their wheels on an empty set of built-in firmware for each
> > > firmware request with no true need for it.
> > >
> > > Add a new kconfig entry to represent built-in firmware support more
> > > clearly. This let's knock 3 birds with one stone:
> > >
> > > o Clarifies that support for built-in firmware requires the
> > > firmware loader to be built-in to the kernel
> > >
> > > o By default we now always skip built-in firmware even if a FW_LOADER=y
> > >
> > > o This also lets us make it clear that the EXTRA_FIRMWARE_DIR
> > > kconfig entry is only used for built-in firmware
> > >
> > > Reviewed-by: Borislav Petkov <bp@xxxxxxx>
> > > Signed-off-by: Luis Chamberlain <mcgrof@xxxxxxxxxx>
> > > ---
> > > .../driver-api/firmware/built-in-fw.rst | 2 ++
> > > Documentation/x86/microcode.rst | 5 ++--
> > > drivers/base/firmware_loader/Kconfig | 25 +++++++++++++------
> > > drivers/base/firmware_loader/Makefile | 3 +--
> > > drivers/base/firmware_loader/main.c | 4 +--
> > > 5 files changed, 26 insertions(+), 13 deletions(-)
> > >
> > > diff --git a/Documentation/driver-api/firmware/built-in-fw.rst b/Documentation/driver-api/firmware/built-in-fw.rst
> > > index bc1c961bace1..9dd2b1df44f0 100644
> > > --- a/Documentation/driver-api/firmware/built-in-fw.rst
> > > +++ b/Documentation/driver-api/firmware/built-in-fw.rst
> > > @@ -8,6 +8,7 @@ the filesystem. Instead, firmware can be looked for inside the kernel
> > > directly. You can enable built-in firmware using the kernel configuration
> > > options:
> > >
> > > + * CONFIG_FW_LOADER_BUILTIN
> > > * CONFIG_EXTRA_FIRMWARE
> > > * CONFIG_EXTRA_FIRMWARE_DIR
> > >
> > > @@ -17,6 +18,7 @@ into the kernel with CONFIG_EXTRA_FIRMWARE:
> > > * Speed
> > > * Firmware is needed for accessing the boot device, and the user doesn't
> > > want to stuff the firmware into the boot initramfs.
> > > +* Testing built-in firmware
> > >
> > > Even if you have these needs there are a few reasons why you may not be
> > > able to make use of built-in firmware:
> > > diff --git a/Documentation/x86/microcode.rst b/Documentation/x86/microcode.rst
> > > index a320d37982ed..d199f0b98869 100644
> > > --- a/Documentation/x86/microcode.rst
> > > +++ b/Documentation/x86/microcode.rst
> > > @@ -114,11 +114,12 @@ Builtin microcode
> > > =================
> > >
> > > The loader supports also loading of a builtin microcode supplied through
> > > -the regular builtin firmware method CONFIG_EXTRA_FIRMWARE. Only 64-bit is
> > > -currently supported.
> > > +the regular builtin firmware method using CONFIG_FW_LOADER_BUILTIN and
> > > +CONFIG_EXTRA_FIRMWARE. Only 64-bit is currently supported.
> > >
> > > Here's an example::
> > >
> > > + CONFIG_FW_LOADER_BUILTIN=y
> > > CONFIG_EXTRA_FIRMWARE="intel-ucode/06-3a-09 amd-ucode/microcode_amd_fam15h.bin"
> > > CONFIG_EXTRA_FIRMWARE_DIR="/lib/firmware"
> > >
> > > diff --git a/drivers/base/firmware_loader/Kconfig b/drivers/base/firmware_loader/Kconfig
> > > index 5b24f3959255..de4fcd9d41f3 100644
> > > --- a/drivers/base/firmware_loader/Kconfig
> > > +++ b/drivers/base/firmware_loader/Kconfig
> > > @@ -29,8 +29,10 @@ if FW_LOADER
> > > config FW_LOADER_PAGED_BUF
> > > bool
> > >
> > > -config EXTRA_FIRMWARE
> > > - string "Build named firmware blobs into the kernel binary"
> > > +config FW_LOADER_BUILTIN
> > > + bool "Enable support for built-in firmware"
> > > + default n
> >
> > n is always the default, no need to list it again.
>
> Oh, alrighty, I'll remove that line.
>
> > > + depends on FW_LOADER=y
> >
> > I don't see what this gets us to add another config option. Are you
> > making things easier later on?
>
> This makes a few things clearer for both developers and users.
> The code in question is a *feature* *only* when FW_LOADER=y, by
> adding a new kconfig to represent this and clearly makeing it
> depend on FW_LOADER=y it let's us:
>
> o Clarify that support for built-in firmware requires
> the firmware loader to be built-in to the kernel
That is good.
> o By default we now always skip built-in firmware even if a FW_LOADER=y
I do not understand, why would we ever want to skip built-in firmware?
> o This also lets us make it clear that the EXTRA_FIRMWARE_DIR
> kconfig entry is only used for built-in firmware
How was it ever used for anything else? :)
> The above is not easily obvious to developers (including myself when
> I was reviewing this code) or users without this new kconfig entry.
>
> Should I re-send by just removing the one line you asked for?
I can not take this as-is, so yes :)
thanks,
greg k-h