Messages in this thread | | | Date | Wed, 11 Dec 2019 11:01:49 +0900 | From | Sergey Senozhatsky <> | Subject | Re: [RFC/PATCH] printk: Fix preferred console selection with multiple matches |
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On (19/12/11 09:26), Benjamin Herrenschmidt wrote: [..] > No not exactly. Architectures/platforms use add_preferred_console() > (such as arm64 with ACPI but powerpc at least does it too) based on > various factors to select a reasonable "default" for that specific > platform. Without that the kernel will basically default to the first > one to register which may not be what you want. > > The command line ones however want to override the defaults (provided > they exist, ie, it's possible that whever is specified on the command > line doesn't actually exist, and thus shall be ignored. That typically > happens when there is either no match or ->setup fails). > > > Hmm. > > > > The patch may affect setups where alias matching is expected to > > happen. E.g.: > > > > console=uartFOO,BAR > > > > Is 8250 the only console that does alias matching? > > Why would the patch affect this negatively ? Today we stop on the first > match, mark the driver enabled, and make it preferred if the match > index matches preferred_console.
As far as I know, ->match() does not only match but also does ->setup(). If we have two console list entries that match (one via aliasing and one via exact match) then the console driver is setup twice. Do all console drivers handle it? [double setup]
If we could perform simple alias matching, without ->setup() call, and exact matching (strcmp()), and then, if newcon would match two entries, we would pick up the last matching entry and configure newcon only once.
This changes the order, tho.
[..] > - Another match that is marked preferred_console, in which case in > addition to being enabled, the newly registered console will also be > made the default console (ie, first in the list with CONSDEV set). This > is actually what we want ! IE. The console matches the last specified > one on the command line.
Well, it still looks to me that what you want is to "ignore alias match and prefer exact match".
-ss
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