Hi Sascha,
On 22. 02. 19 08:49, Sascha Hauer wrote:
On Thu, Feb 21, 2019 at 10:28:48AM +0100, Tomaz Solc wrote:
This commit adds an of_bootargs command that extracts a bootargs
property from a device tree and saves it to a global variable.
For example, a bootloader environment can use this command to extract
the bootargs to linux.bootargs.vc, which then gets included into the
final bootargs for the kernel using CONFIG_FLEXIBLE_BOOTARGS.
Do we need an extra command for this? Can't you just unflatten the
VideoCore provided device tree in the board code you have added in 2/3
and set global.linux.bootargs.vc from there? It seems to be just the
right thing without further user intervention.
I wanted to keep things flexible. I thought having an explicit command
to import the args into Barebox is better than doing this automatically
in rpi-common.c.
As far as I know [1], upstream kernels use their own device tree and
don't need bootargs and fdt from VideoCore. On the other hand, I'm using
the Raspbian-supplied kernels that do depend on these two things. That's
also why I liked the approach where the VideoCore fdt is saved into a
file, where it can be passed to boot or not, depending on the environment.
If you think of_bootargs is too specific for a command, I can make it
more general and have it save an arbitrary property from a fdt into a
global variable (something similar to readf). That might be useful for
something else as well.
[1]
https://elinux.org/RPi_Upstream_Kernel_Compilation#Building_your_bootloader
Best regards
Tomaž
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