earlycon.c

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#include <core/kargs.h>
#include <core/string.h>
#include <console/earlycon.h>
 
static struct earlycon *earlycon;
 
extern struct earlycon earlycon_uart;
extern struct earlycon earlycon_vga;
extern struct earlycon earlycon_fb;
 
extern int earlycon_fb_available(void);
 
/*
 * Writes a string on the early console.
 */
int earlycon_puts(char *s)
{
    return earlycon->puts(s);
}
 
/*
 * Writes a character on the early console.
 */
int earlycon_putc(char c)
{
    return earlycon->putc(c);
}
 
/*
 * Says whether the early console writes on the screen rather than on the
 * serial port.
 */
int earlycon_on_screen(void)
{
    return earlycon != &earlycon_uart;
}
 
/* Starts the early console, on the first serial port, at boot. */
void earlycon_init()
{
    earlycon = &earlycon_uart;
    earlycon->init();
}
 
/* Chooses the early console again once the kernel's command line is
 * read: the framebuffer if there is one, unless `earlycon=` says
 * otherwise. */
void earlycon_reinit()
{
    const char *arg_earlycon = NULL;
    /* the framebuffer if there is one, else the serial port */
    earlycon = earlycon_fb_available() ? &earlycon_fb : &earlycon_uart;
 
    if (!kargs_get("earlycon", &arg_earlycon) && arg_earlycon) {
        if (!strcmp(arg_earlycon, "ttyS0"))
            earlycon = &earlycon_uart;
        else if (!strcmp(arg_earlycon, "vga"))
            earlycon = &earlycon_vga;
        else if (!strcmp(arg_earlycon, "fb") && earlycon_fb_available())
            earlycon = &earlycon_fb;
    }
 
    earlycon->init();
}