Re: [patch] early printk and boot console fixups.

[Bjorn Helgaas <bjorn.helgaas@hp.com>]

On Wednesday 16 May 2007 10:29:11 am Yinghai Lu wrote:
> On 5/16/07, Bjorn Helgaas <bjorn.helgaas@hp.com> wrote:
> > On Tuesday 15 May 2007 10:17:50 pm Yinghai Lu wrote:
> > > for early_uart_console, I have some ideas:
> > > 1. merged that into early_serial_console in
> > > arch/x86_64/kernel/early_printk.c, and
> > > move early_printk.c to kernel/, --- make it understand
> > >      earlyprintk=uart,io,0x3f8,9600n8
> > >      earlyprintk=uart,mmio,0xff5e0000,115200n8
> > > in addition to vga, ttyS, serial
> >
> > I would rather try to merge 8250_early and early_printk.
> > "console=uart,io,0x3f8" is already pretty similar to
> > "earlyprintk=serial", and it would be nice to have only one.
> >
> > "console=uart" does have the disadvantage that you have to know the
> > port address.  But it has the advantage that it doesn't depend on
> > compiled-in legacy serial port names.  If you need early console
> > output, you're probably a developer and can come up with the address.
> >
> > I think it would be nice to have a "console=vga".  That could use
> > the current "earlyprintk=vga" implementation, and automatically
> > hand off to tty0.
> >
> > Then we could remove "earlyprintk=" and always use "console=uart"
> > or "console=vga".
> 
> earlyprintk= is needed for seeting bootconsole, or setting CON_BOOT,
> and it is could be loaded earlier with early_param than console_init.

8250_early.c does basically the same thing as the serial part of
early_printk.c, so we should be able to make it work just as early.
I don't remember why I didn't use early_param() for 8250_early;
I probably should have.  On ia64, it doesn't matter because we call
early_serial_console_init() explicitly at about the time of
parse_early_param().

8250_early and early_printk are so similar, I just don't see the
need for both.

Bjorn