[Buildroot] [PATCH-NEXT 4/4] linux: build after linux-firmware if enabled for early loading support

[Peter Korsgaard <peter@korsgaard.com>]

>>>>> "Yann" == Yann E MORIN <yann.morin.1998@free.fr> writes:

 > On 2021-02-12 19:40 +0100, Peter Korsgaard spake thusly:
 >> To support building in (a subset of) the linux-firmware files into the
 >> kernel using the CONFIG_EXTRA_FIRMWARE option, we need to ensure that the
 >> firmware files are installed before the Linux kernel is built, similar to
 >> how it is done for intel-microcode.
 >> 
 >> Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
 >> ---
 >> linux/linux.mk | 3 ++-
 >> 1 file changed, 2 insertions(+), 1 deletion(-)
 >> 
 >> diff --git a/linux/linux.mk b/linux/linux.mk
 >> index a212f42c28..5e4b319cf1 100644
 >> --- a/linux/linux.mk
 >> +++ b/linux/linux.mk
 >> @@ -78,7 +78,8 @@ LINUX_MAKE_ENV = \
 >> 
 >> LINUX_INSTALL_IMAGES = YES
 >> LINUX_DEPENDENCIES = host-kmod \
 >> -	$(if $(BR2_PACKAGE_INTEL_MICROCODE),intel-microcode)
 >> +	$(if $(BR2_PACKAGE_INTEL_MICROCODE),intel-microcode) \
 >> +	$(if $(BR2_PACKAGE_LINUX_FIRMWARE),linux-firmware)

 > You also need to tell the kernel where to find those firmware files,
 > with CONFIG_EXTRA_FIRMWARE_DIR, otherwise it will look in /lib/firmware.

Yes, but that you can take care of in linux config file/fragment. We
already expose BR2_BINARIES_DIR in the environment for this, E.G. you
can do:

CONFIG_EXTRA_FIRMWARE_DIR="${BR_BINARIES_DIR}"
CONFIG_EXTRA_FIRMWARE="intel-ucode/06-5e-03 i915/kbl_dmc_ver1_04.bin"

(or whatever files you want to include).

 > So we'd need something like:

 >     $(if $(BR2_PACKAGE_LINUX_FIRMWARE),
 >         $(call KCONFIG_SET_OPT,CONFIG_EXTRA_FIRMWARE_DIR,"$${BR_BINARIES_DIR}/linux-firmware"))

NIT: Only ${BR_BINARIES_DIR}, not a linux-firmware subdir, otherwise you
cannot include both microcode and linux-firmware files.


 > (note the $$ escaping and the use of a shell-level variable, like is
 > done for CONFIG_INITRAMFS_SOURCE).

Given that the user already has to use a custom kernel config
file/fragment to specify what files to include, I don't think it makes
sense to override the CONFIG_EXTRA_FIRMWARE_DIR setting. We don't do it
for intel-microcode either.

-- 
Bye, Peter Korsgaard