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authorTakashi Iwai <tiwai@suse.de>2020-03-30 13:43:00 +0200
committerTakashi Iwai <tiwai@suse.de>2020-03-30 13:43:00 +0200
commit3c22baeab40b2f8e75907cfd7aa69147d5343d2c (patch)
treee8300e52242ae3a9c7bfe6089ee7125324095e27 /Documentation/admin-guide/bootconfig.rst
parentaa21c3d4b941739651e77747d2f7a20a6c1d87bc (diff)
parent1c521d7e62262793789845989edca57dea24eb7d (diff)
Merge tag 'asoc-v5.7' of https://git.kernel.org/pub/scm/linux/kernel/git/broonie/sound into for-linus
ASoC: Updates for v5.7 This is a very big update for the core since Morimoto-san has been rather busy continuing his refactorings to clean up a lot of the cruft that we have accumilated over the years. We've also gained several new drivers, including initial (but still not complete) parts of the Intel SoundWire support. - Lots of refactorings to modernize the code from Morimoto-san. - Conversion of SND_SOC_ALL_CODECS to use imply from Geert Uytterhoeven. - Continued refactoring and fixing of the Intel support. - Soundwire and more advanced clocking support for Realtek RT5682. - Support for amlogic GX, Meson 8, Meson 8B and T9015 DAC, Broadcom DSL/PON, Ingenic JZ4760 and JZ4770, Realtek RL6231, and TI TAS2563 and TLV320ADCX140.
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.