Hi Peter 2015-10-21 22:20 GMT+09:00 Peter Hurley <peter@xxxxxxxxxxxxxxxxxx>: > On 10/21/2015 04:21 AM, Masahiro Yamada wrote: >> Hi. >> >> >> >> >> I think there are three places where console could be enabled. >> >> [1] earlycon >> >> Each driver entry is declared with >> EARLYCON_DECLARE() or OF_EARLYCON_DECLARE() >> >> >> >> [2] console_init() >> >> Each entry is declared with console_initcall() >> >> >> >> [3] when driver is probed >> The console is usually enabled at this point >> unless some special treatment is done. >> >> >> >> >> My question is about [2]. > > For 8250 sub-drivers, the console_initcall() is only for legacy > platforms, and not for 8250 ports added via serial8250_register_8250_port(). > > In this contexts, legacy platforms are: > 1. early_serial_setup() > 2. platforms that define SERIAL_PORT_DFNS (eg., ISA ports) > > > At the point where console_initcall() occurs, the 8250 core has _not_ > been initialized (ie., serial8250_init() has _not_ run). > > > >> I am using 8250-ish UART device. >> >> >> I noticed univ8250_console_match() and univ8250_console_setup() >> always fail at the point of [2] unless early_serial_setup() has been >> called in advance; >> however, it looks like early_serial_setup() is only used for old platforms. >> >> So, console cannot be enabled at [2] for modern platforms. > > Since console_init() => console_initcall() occurs before almost everything, > it's not practical to use for probed drivers. > > >> My questions are: >> >> - Given that earlycon can be now available for major architectures such ARM, >> [2] will be deprecated at some point in the future? > > PPC and x86 platforms still rely on console_init() so it will be some time > before this disappears. > >> - I am implementing earlycon for my own UART driver. >> Is it meaningless to implement console_initcall() as well as earlycon? > > Probed drivers should only implement earlycon and console. 8250 sub-drivers > should only implement earlycon and/or console if the base 8250 earlycon and/or > console are not operational. Sorry, let me to be sure a bit. Which does "console" in this context mean - console_initcall - console enabled when the driver is probed I am assuming the latter. Thanks, -- Best Regards Masahiro Yamada -- To unsubscribe from this list: send the line "unsubscribe linux-serial" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
