On 5/24/21 11:15 AM, Andre Przywara wrote:
On Mon, 24 May 2021 10:37:31 -0400 Sean Anderson sean.anderson@seco.com wrote:
On 5/23/21 8:36 PM, Andre Przywara wrote:
At the moment the fastboot code relies on the Kconfig variable CONFIG_FASTBOOT_FLASH_MMC_DEV to point to the MMC device to use for the flash command. This value needs to be the *U-Boot device number*, which is picked by the U-Boot device model at runtime. This makes it quite tricky and fragile to fix this variable at compile time, as other DT nodes and aliases influence the enumeration process.
To make this process more robust, allow the device number to be picked at runtime, which sounds like a better fit to find this device number. Patch 1/3 introduces a weak function for that purpose. Patch 2/3 then implements this function for the Allwinner platform. The code follows the idea behind the existing Kconfig defaults: Use the eMMC device, if that exists, or the SD card otherwise. This patch is actually not sunxi specific, so might be adopted by other platforms as well. Patch 3/3 then drops the existing Kconfig defaults for sunxi, to clean this up and remove the implicit assumption that the eMMC device is always device 1 (as least for the fastboot code).
I would be curious if others think this is the right way forward. The fact that the U-Boot device numbers are determined at runtime seems to conflict with the idea of a Kconfig variable in the first place, hence this series. This brings us one step closer to the end goal of removing the "eMMC is device 1" assumption.
I would actually favor removing CONFIG_FASTBOOT_FLASH_MMC_DEV altogether, and just specifying the device explicitly in fastboot commands. If you need to dynamically change the device, you can create some aliases. E.g. you could have something like
"fastboot_aliases=setenv fastboot_partition_alias_user ${mmcdev}.0:0"
and then run this variable just before calling `fastboot 0` (or whatever your usb device is).
Fine with me. I was actually wondering about this already, but didn't want to disrupt every user, especially since I can't really test this very well.
The ideal way would be to define aliases dynamically mapping old partition names to new syntax. So if the U-Boot shell were a bit more expressive, one could do
for partition in $(mmc part list $mmcdev); do env set fastboot_partition_alias_${partition} ${mmcdev}#${partition} done fastboot usb 0
which would map old partition names to new-style syntax. Unfortunately, we don't quite have that capability yet. I think defining a bunch of aliases when you run fastboot could be... suprising. I'm not sure if there is a good solution here.
So can you use this explicit device naming from the host side already with the current code? Can you give an example how this would look like?
Flash the partition named "rootfs" on MMC 0 hardware partition 0
$ fastboot flash 0#rootfs root.simg
Flash the entirety of MMC 1 hardware partition 2
$ fastboot flash 1.2:0 boot2.img
For a more thorough treatment of this syntax, see [1]
The documentation I could find only speaks of the Android partition names (like "system"), which requires environment variables to work, IIUC?
They require that you use a GPT-formatted disk with partition labels. Alternatively, you can use aliases. There is one sentence on the new-style syntax here [2], but I really should expand on it...
--Sean
[1] https://u-boot.readthedocs.io/en/latest/usage/partitions.html#partitions [2] https://u-boot.readthedocs.io/en/latest/android/fastboot.html#partition-name...
Thanks, Andre
I am looking forward to any comments on this series!
Cheers, Andre
Andre Przywara (3): fastboot: Allow runtime determination of MMC device sunxi: Implement fastboot_get_mmc_device() sunxi: Drop sunxi FASTBOOT_FLASH_MMC_DEV defaults
board/sunxi/board.c | 37 +++++++++++++++++++++++++++++++++++ drivers/fastboot/Kconfig | 4 +--- drivers/fastboot/fb_command.c | 6 +++--- drivers/fastboot/fb_common.c | 3 ++- drivers/fastboot/fb_mmc.c | 12 ++++++++---- include/fastboot.h | 7 +++++++ 6 files changed, 58 insertions(+), 11 deletions(-)