aboutsummaryrefslogtreecommitdiffstats
path: root/Documentation/admin-guide/bootconfig.rst
diff options
context:
space:
mode:
authorOlof Johansson <olof@lixom.net>2020-03-03 16:40:54 -0800
committerOlof Johansson <olof@lixom.net>2020-03-03 16:40:56 -0800
commit820d15632ec10bc0cf79595c5a635b795d149520 (patch)
tree9deb7defafc350a3c74365ebe370634f0406d821 /Documentation/admin-guide/bootconfig.rst
parentMerge tag 'arm-soc/for-5.6/defconfig-fixes' of https://github.com/Broadcom/stblinux into arm/fixes (diff)
parentarm64: dts: socfpga: agilex: Fix gmac compatible (diff)
downloadlinux-dev-820d15632ec10bc0cf79595c5a635b795d149520.tar.xz
linux-dev-820d15632ec10bc0cf79595c5a635b795d149520.zip
Merge tag 'socfpga_dts_fix_for_v5.6_v2' of git://git.kernel.org/pub/scm/linux/kernel/git/dinguyen/linux into arm/fixes
arm64: dts: agilex: fix gmac compatible - The compatible for Agilex GMAC should be "altr,socfpga-stmmac-a10-s10" * tag 'socfpga_dts_fix_for_v5.6_v2' of git://git.kernel.org/pub/scm/linux/kernel/git/dinguyen/linux: (578 commits) arm64: dts: socfpga: agilex: Fix gmac compatible Linux 5.6-rc4 KVM: VMX: check descriptor table exits on instruction emulation ext4: potential crash on allocation error in ext4_alloc_flex_bg_array() macintosh: therm_windtunnel: fix regression when instantiating devices jbd2: fix data races at struct journal_head kvm: x86: Limit the number of "kvm: disabled by bios" messages KVM: x86: avoid useless copy of cpufreq policy KVM: allow disabling -Werror KVM: x86: allow compiling as non-module with W=1 KVM: Pre-allocate 1 cpumask variable per cpu for both pv tlb and pv ipis KVM: Introduce pv check helpers KVM: let declaration of kvm_get_running_vcpus match implementation KVM: SVM: allocate AVIC data structures based on kvm_amd module parameter MAINTAINERS: Correct Cadence PCI driver path io_uring: fix 32-bit compatability with sendmsg/recvmsg net: dsa: mv88e6xxx: Fix masking of egress port mlxsw: pci: Wait longer before accessing the device after reset sfc: fix timestamp reconstruction at 16-bit rollover points vsock: fix potential deadlock in transport->release() ... Link: https://lore.kernel.org/r/20200303153509.28248-1-dinguyen@kernel.org Signed-off-by: Olof Johansson <olof@lixom.net>
Diffstat (limited to 'Documentation/admin-guide/bootconfig.rst')
-rw-r--r--Documentation/admin-guide/bootconfig.rst34
1 files changed, 31 insertions, 3 deletions
diff --git a/Documentation/admin-guide/bootconfig.rst b/Documentation/admin-guide/bootconfig.rst
index b342a6796392..cf2edcd09183 100644
--- a/Documentation/admin-guide/bootconfig.rst
+++ b/Documentation/admin-guide/bootconfig.rst
@@ -62,6 +62,30 @@ Or more shorter, written as following::
In both styles, same key words are automatically merged when parsing it
at boot time. So you can append similar trees or key-values.
+Same-key Values
+---------------
+
+It is prohibited that two or more values or arrays share a same-key.
+For example,::
+
+ foo = bar, baz
+ foo = qux # !ERROR! we can not re-define same key
+
+If you want to append the value to existing key as an array member,
+you can use ``+=`` operator. For example::
+
+ foo = bar, baz
+ foo += qux
+
+In this case, the key ``foo`` has ``bar``, ``baz`` and ``qux``.
+
+However, a sub-key and a value can not co-exist under a parent key.
+For example, following config is NOT allowed.::
+
+ foo = value1
+ foo.bar = value2 # !ERROR! subkey "bar" and value "value1" can NOT co-exist
+
+
Comments
--------
@@ -102,9 +126,13 @@ Boot Kernel With a Boot Config
==============================
Since the boot configuration file is loaded with initrd, it will be added
-to the end of the initrd (initramfs) image file. The Linux kernel decodes
-the last part of the initrd image in memory to get the boot configuration
-data.
+to the end of the initrd (initramfs) image file with size, checksum and
+12-byte magic word as below.
+
+[initrd][bootconfig][size(u32)][checksum(u32)][#BOOTCONFIG\n]
+
+The Linux kernel decodes the last part of the initrd image in memory to
+get the boot configuration data.
Because of this "piggyback" method, there is no need to change or
update the boot loader and the kernel image itself.