arch/s390/kernel/early_printk.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  *    Copyright IBM Corp. 2017
   4  */
   5
   6 #include <linux/console.h>
   7 #include <linux/kernel.h>
   8 #include <linux/init.h>
   9 #include <asm/setup.h>
  10 #include <asm/sclp.h>
  11
  12 static void sclp_early_write(struct console *con, const char *s, unsigned int len)
  13 {
  14         __sclp_early_printk(s, len);
  15 }
  16
  17 static struct console sclp_early_console = {
  18         .name  = "earlysclp",
  19         .write = sclp_early_write,
  20         .flags = CON_PRINTBUFFER | CON_BOOT,
  21         .index = -1,
  22 };
  23
  24 void __init register_early_console(void)
  25 {
  26         if (early_console)
  27                 return;
  28         if (!sclp.has_linemode && !sclp.has_vt220)
  29                 return;
  30         early_console = &sclp_early_console;
  31         register_console(early_console);
  32 }
  33
  34 static int __init setup_early_printk(char *buf)
  35 {
  36         if (early_console)
  37                 return 0;
  38         /* Accept only "earlyprintk" and "earlyprintk=sclp" */
  39         if (buf && !str_has_prefix(buf, "sclp"))
  40                 return 0;
  41         register_early_console();
  42         return 0;
  43 }
  44 early_param("earlyprintk", setup_early_printk);