| Message ID | 1544634754-3435-7-git-send-email-ruslan.trofymenko@linaro.org |
|---|---|
| State | Accepted |
| Commit | ae954baf3bf73ff4ae436e080444e91f54b8aebf |
| Headers | show |
| Series | android: Implement A/B boot process | expand |
On Wed, 12 Dec 2018 at 10:12, Ruslan Trofymenko <ruslan.trofymenko@linaro.org> wrote: > > Add a short documentation for A/B enablement and 'ab_select' command > usage. > > Signed-off-by: Ruslan Trofymenko <ruslan.trofymenko@linaro.org> > Reviewed-by: Alistair Strachan <astrachan@google.com> > Reviewed-by: Sam Protsenko <semen.protsenko@linaro.org> > --- > Changes in v2: > * Сhanges related to command renaming (android_ab_select -> ab_select) > > doc/README.android-ab | 67 +++++++++++++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 67 insertions(+) > create mode 100644 doc/README.android-ab Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Igor Opaniuk <igor.opaniuk@linaro.org> On Wed, 12 Dec 2018 at 19:12, Ruslan Trofymenko <ruslan.trofymenko@linaro.org> wrote: > > Add a short documentation for A/B enablement and 'ab_select' command > usage. > > Signed-off-by: Ruslan Trofymenko <ruslan.trofymenko@linaro.org> > Reviewed-by: Alistair Strachan <astrachan@google.com> > Reviewed-by: Sam Protsenko <semen.protsenko@linaro.org> > --- > Changes in v2: > * Сhanges related to command renaming (android_ab_select -> ab_select) > > doc/README.android-ab | 67 +++++++++++++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 67 insertions(+) > create mode 100644 doc/README.android-ab > > diff --git a/doc/README.android-ab b/doc/README.android-ab > new file mode 100644 > index 0000000..9f37ed5 > --- /dev/null > +++ b/doc/README.android-ab > @@ -0,0 +1,67 @@ > +Android A/B updates > +=================== > + > +Overview > +-------- > + > +A/B system updates ensures modern approach for system update. This feature > +allows one to use two sets (or more) of partitions referred to as slots > +(normally slot A and slot B). The system runs from the current slot while the > +partitions in the unused slot can be updated [1]. > + > +A/B enablement > +-------------- > + > +The A/B updates support can be activated by specifying next options in > +your board configuration file: > + > + CONFIG_ANDROID_AB=y > + CONFIG_CMD_AB_SELECT=y > + > +The disk space on target device must be partitioned in a way so that each > +partition which needs to be updated has two or more instances. The name of > +each instance must be formed by adding suffixes: _a, _b, _c, etc. > +For example: boot_a, boot_b, system_a, system_b, vendor_a, vendor_b. > + > +As a result you can use 'ab_select' command to ensure A/B boot process in your > +boot script. This command analyzes and processes A/B metadata stored on a > +special partition (e.g. "misc") and determines which slot should be used for > +booting up. > + > +Command usage > +------------- > + > + ab_select <slot_var_name> <interface> <dev[:part_number|#part_name]> > + > +for example: > + > + => ab_select slot_name mmc 1:4 > + > +or > + > + => ab_select slot_name mmc 1#misc > + > +Result: > + > + => printenv slot_name > + slot_name=a > + > +Based on this slot information, the current boot partition should be defined, > +and next kernel command line parameters should be generated: > + > + - androidboot.slot_suffix= > + - root= > + > +For example: > + > + androidboot.slot_suffix=_a root=/dev/mmcblk1p12 > + > +A/B metadata is organized according to AOSP reference [2]. On the first system > +start with A/B enabled, when 'misc' partition doesn't contain required data, > +the default A/B metadata will be created and written to 'misc' partition. > + > +References > +---------- > + > +[1] https://source.android.com/devices/tech/ota/ab > +[2] bootable/recovery/bootloader_message/include/bootloader_message/bootloader_message.h > -- > 2.7.4 >
diff --git a/doc/README.android-ab b/doc/README.android-ab new file mode 100644 index 0000000..9f37ed5 --- /dev/null +++ b/doc/README.android-ab @@ -0,0 +1,67 @@ +Android A/B updates +=================== + +Overview +-------- + +A/B system updates ensures modern approach for system update. This feature +allows one to use two sets (or more) of partitions referred to as slots +(normally slot A and slot B). The system runs from the current slot while the +partitions in the unused slot can be updated [1]. + +A/B enablement +-------------- + +The A/B updates support can be activated by specifying next options in +your board configuration file: + + CONFIG_ANDROID_AB=y + CONFIG_CMD_AB_SELECT=y + +The disk space on target device must be partitioned in a way so that each +partition which needs to be updated has two or more instances. The name of +each instance must be formed by adding suffixes: _a, _b, _c, etc. +For example: boot_a, boot_b, system_a, system_b, vendor_a, vendor_b. + +As a result you can use 'ab_select' command to ensure A/B boot process in your +boot script. This command analyzes and processes A/B metadata stored on a +special partition (e.g. "misc") and determines which slot should be used for +booting up. + +Command usage +------------- + + ab_select <slot_var_name> <interface> <dev[:part_number|#part_name]> + +for example: + + => ab_select slot_name mmc 1:4 + +or + + => ab_select slot_name mmc 1#misc + +Result: + + => printenv slot_name + slot_name=a + +Based on this slot information, the current boot partition should be defined, +and next kernel command line parameters should be generated: + + - androidboot.slot_suffix= + - root= + +For example: + + androidboot.slot_suffix=_a root=/dev/mmcblk1p12 + +A/B metadata is organized according to AOSP reference [2]. On the first system +start with A/B enabled, when 'misc' partition doesn't contain required data, +the default A/B metadata will be created and written to 'misc' partition. + +References +---------- + +[1] https://source.android.com/devices/tech/ota/ab +[2] bootable/recovery/bootloader_message/include/bootloader_message/bootloader_message.h