Messages in this thread | | | From | Chris Packham <> | Subject | Re: [PATCH] arm64: Support CMDLINE_EXTEND | Date | Tue, 21 Mar 2023 20:16:14 +0000 |
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On 22/03/23 08:06, Mark Brown wrote: > On Tue, Mar 21, 2023 at 11:19:55AM +0000, Mark Rutland wrote: > >> We deliberately dropped support for CMDLINE_EXTEND in commit: >> cae118b6acc3 ("arm64: Drop support for CMDLINE_EXTEND") >> ... which was mentioned the last time somone tried to re-add it: >> https://lore.kernel.org/linux-arm-kernel/ZAh8dWvbNkVQT11C@arm.com/ >> Has something changes such that those issues no longer apply?
I'm not sure I see any "issues" (although perhaps that's just me not being able to find the rest of the series on lore).
My specific use case is that I want to have the sbsa_gwdt watchdog driver built-in to the kernel but I also want it to produce panic output instead of silently resetting the board so I want to have sbsa_gwdt.action=1 in my kernel command line. Either appending or prepending that on the command line would work for me.
>> If so, please >> call that out explicitly in the commit message. If not, I do not think we >> should take this patch.
To save a click here is the relevant part from cae118b6acc3
The documented behaviour for CMDLINE_EXTEND is that the arguments from the bootloader are appended to the built-in kernel command line. This also matches the option parsing behaviour for the EFI stub and early ID register overrides.
Bizarrely, the fdt behaviour is the other way around: appending the built-in command line to the bootloader arguments, resulting in a command-line that doesn't necessarily line-up with the parsing order and definitely doesn't line-up with the documented behaviour.
This appears to be a current problem for arm an powerpc. If it weren't for the fact that EFI version had different behaviour I'd be suggesting just updating the help text. Maybe that should be done anyway regardless of any unification so that the documentation reflects reality.
> Given that there have been multiple attempts to readd it is it worth > documenting this in the code?
The proposed CMDLINE_APPEND would work well for my use-case but two attempts at landing such generic support seem to have failed. I could attempt to resurrect [1] or the alternative [2] but I'm worried I'll end up with the same road blocks. Also looks like I just found a 3rd [3].
I hope I haven't kicked a hornets nest here.
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[1] - https://lore.kernel.org/lkml/20190319232448.45964-2-danielwa@cisco.com/ [2] - https://patchwork.ozlabs.org/project/linuxppc-dev/cover/cover.1554195798.git.christophe.leroy@c-s.fr/ [3] - https://lore.kernel.org/lkml/20210416040924.2882771-1-danielwa@cisco.com/
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