Hello Rob, On Tue, 2022-12-13 at 09:29 -0600, Rob Herring wrote: > On Tue, Dec 13, 2022 at 09:51:33AM +0100, Linus Walleij wrote: > > On Mon, Dec 12, 2022 at 7:01 AM Alexander Sverdlin > > <alexander.sverdlin@xxxxxxxxx> wrote: > > > > > I do not read a strict requirement on /chosen node in either ePAPR or in > > > Documentation/devicetree. Help text for CONFIG_CMDLINE and > > > CONFIG_CMDLINE_EXTEND doesn't make their behavior explicitly dependent on > > > the presence of /chosen or the presense of /chosen/bootargs. > > > > > > However the early check for /chosen and bailing out in > > > early_init_dt_scan_chosen() skips CONFIG_CMDLINE handling which is not > > > really related to /chosen node or the particular method of passing cmdline > > > from bootloader. > > > > > > This leads to counterintuitive combinations (assuming > > > CONFIG_CMDLINE_EXTEND=y): > > > > > > a) bootargs="foo", CONFIG_CMDLINE="bar" => cmdline=="foo bar" > > > b) /chosen missing, CONFIG_CMDLINE="bar" => cmdline=="" > > > c) bootargs="", CONFIG_CMDLINE="bar" => cmdline==" bar" > > > > > > Move CONFIG_CMDLINE handling outside of early_init_dt_scan_chosen() so that > > > cases b and c above result in the same cmdline. > > > > > > Signed-off-by: Alexander Sverdlin <alexander.sverdlin@xxxxxxxxx> > > > > Excellent debugging Alexander! > > Reviewed-by: Linus Walleij <linus.walleij@xxxxxxxxxx> > > > > I also think this should go to stable. > > We have to be careful there. This could change behavior on a working > system. A system taking the cmdline entirely from a built kernel and > no initrd is going to be pretty customized already, I think they can > carry a patch. What platform is this anyways? I've stumbled upon this testing first DT conversion patches for EP93xx (ARM). > This has actually been known for some time[1][2]. My concern in the past > (besides wanting all the cmdline manipulation being common) was MIPS. This "change of behavior" actually changes one exact corner case: no /chosen node + CONFIG_CMDLINE!="" + CONFIG_CMDLINE_EXTEND=y If someone was intentionally hiding something in the config file under CONFIG_CMDLINE but didn't want it to appear on the kernel command line in the past, he could just reconfigure new kernel version after the change and remove the above configs. > MIPS in particular has lots of sources for cmdline and ways to combine > it. However, MIPS has since stopped using this code and does their own > parsing (not great either IMO). I agree, this code screams to be common. -- Alexander Sverdlin.
