Messages in this thread | | | Date | Wed, 11 Dec 2019 13:53:03 +0100 | From | Petr Mladek <> | Subject | Re: [RFC/PATCH] printk: Fix preferred console selection with multiple matches |
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On Wed 2019-12-11 15:02:02, Benjamin Herrenschmidt wrote: > On Wed, 2019-12-11 at 11:01 +0900, Sergey Senozhatsky wrote: > > On (19/12/11 09:26), Benjamin Herrenschmidt wrote: > > > > > 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] > > I don't think it's an issue but I may be wrong. I had a quick look > at some of the drivers and I don't really see why they would break but > I couldn't look at them all and I might be mistaken. > > We could skip setup if the console is already enabled but I would > advise against that since the two calls might have different options > (the firmware baud rate could be different from the command line one > for example) and we want the options for the last one.
For example:
+ ip22zilog_console_setup() calls __ip22zilog_startup() that does some initialization of the device
+ pl011_console_setup() does some non-trivial things as well.
Honestly, I am not familiar with these devices. I am not sure if it is dangerous or safe to call these functions twice.
I am not sure if anybody would know this for sure. Therefore I suggest a conservative approach and avoid calling setup() twice().
I think that it is dangerous and error-prone design. The best solution would be to split setup() and match() functionality.
Best Regards, Petr
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