/* * The console driver calls this routine during kernel initialization * to register the console printing procedure with printk() and to * print any messages that were printed by the kernel before the * console driver was initialized. * * This can happen pretty early during the boot process (because of * early_printk) - sometimes before setup_arch() completes - be careful * of what kernel features are used - they may not be initialised yet. * * There are two types of consoles - bootconsoles (early_printk) and * "real" consoles (everything which is not a bootconsole) which are * handled differently. * - Any number of bootconsoles can be registered at any time. * - As soon as a "real" console is registered, all bootconsoles * will be unregistered automatically. * - Once a "real" console is registered, any attempt to register a * bootconsoles will be rejected */ void register_console(struct console *newcon) { ............................ /* * See if this console matches one we selected on * the command line. */ //看上面的注释我们也可以知道了command line中的定义在这里也起作用了 for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++) { if (strcmp(console_cmdline[i].name, newcon->name) != 0) continue; if (newcon->index >= 0 && newcon->index != console_cmdline[i].index) continue; if (newcon->index < 0) newcon->index = console_cmdline[i].index; #ifdef CONFIG_A11Y_BRAILLE_CONSOLE if (console_cmdline[i].brl_options) { newcon->flags |= CON_BRL; braille_register_console(newcon, console_cmdline[i].index, console_cmdline[i].options, console_cmdline[i].brl_options); return; } #endif if (newcon->setup && newcon->setup(newcon, console_cmdline[i].options) != 0)/////在这里可以看到setup的过程了 break; newcon->flags |= CON_ENABLED; newcon->index = console_cmdline[i].index; if (i == selected_console) { newcon->flags |= CON_CONSDEV; preferred_console = selected_console; } break; } if (!(newcon->flags & CON_ENABLED))//其他的console driver屏蔽掉 return; ........................................ }
printk如何定向输出到UART的？
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