Which is the actual console driver used by printk function? (x86, 32bit)

[gfz2004xy]

Hi All:
Which is the actual console driver used by printk function? (x86, 32bit)

When boot the kernel, the printk output message on the monitor,
printk function will run to struct console->write, consw-> con_putcs,
but con_putcs of the vga_con, dummy_con is DUMMY (empty deal).

I want to look for the basic output and input implement of linux kernel,
But confuse on which is the actual console driver used?

Can anybody help me? Thanks.

[GNU-Fan]

If I remember correctly, Linux uses a preliminary output driver during boot first, then later switches to the more sophisticated one. So at some point the dummy entry should get replaced by a pointer to the actual driver.

[gfz2004xy]

Thank you, GNU-Fan.
I' ll try to find it.

[gfz2004xy]

I trace the process by log.

I found before call console_init() func, the console_drivers
is empty list.
But before console_init(), there is also other message
print on the monitor, is printk function has other method
to output on monitor? Not only by console driver?
But I really did't found other output on monitor deal...

[GNU-Fan]

Have you checked the /boot directory. There is a low level printf routine. Most probably somewhere a few bios calls are made in order to put characters on the screen. Maybe a int in the assembler (.S) files.

[gfz2004xy]

Hi, GNU-Fan:
Thanks for answer.

I checked it, Before console_drivers initialized,
the message kept in log_buf,when registered the vt_console，
it will output all the message kept in log_buf one tile.
It's really good.

Now, still a question exist, "vt_console" used "vga_con" as "consw" ,
but vga_con->out_putcs is DUMMY. I'll try to resolve it.