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    Subject[PATCH 05/10] printk,early_printk,console: Allow more than one early console
    Date
    It is very nice to be able to use one early boot device to debug
    another or to have multiple places you can see the early boot
    diagnostics, such as the vga screen or serial device.

    This patch changes the early_printk console device registration to
    allow more than one early printk device to get registered via
    register_console().

    A corresponding change is required to the console registration code
    such that it will properly unregister any console marked with the
    CON_BOOT flag via a simple loop during a console handover or at late
    init time.

    Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
    Cc: Greg KH <gregkh@suse.de>
    Cc: Ingo Molnar <mingo@elte.hu>
    Cc: Andrew Morton <akpm@linux-foundation.org>
    Cc: Yinghai Lu <yinghai@kernel.org>
    Cc: "Eric W. Biederman" <ebiederm@xmission.com>
    Cc: Randy Dunlap <randy.dunlap@oracle.com>
    ---
    arch/x86/kernel/early_printk.c | 65 ++++++++++++++++++++-------------------
    kernel/printk.c | 41 ++++++++++++++++---------
    2 files changed, 59 insertions(+), 47 deletions(-)

    diff --git a/arch/x86/kernel/early_printk.c b/arch/x86/kernel/early_printk.c
    index 519a5e1..2acfd3f 100644
    --- a/arch/x86/kernel/early_printk.c
    +++ b/arch/x86/kernel/early_printk.c
    @@ -176,10 +176,19 @@ asmlinkage void early_printk(const char *fmt, ...)
    va_end(ap);
    }

    +static inline void early_console_register(struct console *con, int keep_early)
    +{
    + early_console = con;
    + if (keep_early)
    + early_console->flags &= ~CON_BOOT;
    + else
    + early_console->flags |= CON_BOOT;
    + register_console(early_console);
    +}

    static int __init setup_early_printk(char *buf)
    {
    - int keep_early;
    + int keep;

    if (!buf)
    return 0;
    @@ -188,42 +197,34 @@ static int __init setup_early_printk(char *buf)
    return 0;
    early_console_initialized = 1;

    - keep_early = (strstr(buf, "keep") != NULL);
    -
    - if (!strncmp(buf, "serial", 6)) {
    - early_serial_init(buf + 6);
    - early_console = &early_serial_console;
    - } else if (!strncmp(buf, "ttyS", 4)) {
    - early_serial_init(buf);
    - early_console = &early_serial_console;
    - } else if (!strncmp(buf, "vga", 3)
    - && boot_params.screen_info.orig_video_isVGA == 1) {
    - max_xpos = boot_params.screen_info.orig_video_cols;
    - max_ypos = boot_params.screen_info.orig_video_lines;
    - current_ypos = boot_params.screen_info.orig_y;
    - early_console = &early_vga_console;
    + keep = (strstr(buf, "keep") != NULL);
    +
    + while (*buf != '\0') {
    + if (!strncmp(buf, "serial", 6)) {
    + early_serial_init(buf + 6);
    + early_console_register(&early_serial_console, keep);
    + }
    + if (!strncmp(buf, "ttyS", 4)) {
    + early_serial_init(buf + 4);
    + early_console_register(&early_serial_console, keep);
    + }
    + if (!strncmp(buf, "vga", 3) &&
    + boot_params.screen_info.orig_video_isVGA == 1) {
    + max_xpos = boot_params.screen_info.orig_video_cols;
    + max_ypos = boot_params.screen_info.orig_video_lines;
    + current_ypos = boot_params.screen_info.orig_y;
    + early_console_register(&early_vga_console, keep);
    + }
    #ifdef CONFIG_EARLY_PRINTK_DBGP
    - } else if (!strncmp(buf, "dbgp", 4)) {
    - if (early_dbgp_init(buf+4) < 0)
    - return 0;
    - early_console = &early_dbgp_console;
    - /*
    - * usb subsys will reset ehci controller, so don't keep
    - * that early console
    - */
    - keep_early = 0;
    + if (!strncmp(buf, "dbgp", 4) && !early_dbgp_init(buf + 4))
    + early_console_register(&early_dbgp_console, keep);
    #endif
    #ifdef CONFIG_HVC_XEN
    - } else if (!strncmp(buf, "xen", 3)) {
    - early_console = &xenboot_console;
    + if (!strncmp(buf, "xen", 3))
    + early_console_register(&xenboot_console, keep);
    #endif
    + buf++;
    }
    -
    - if (keep_early)
    - early_console->flags &= ~CON_BOOT;
    - else
    - early_console->flags |= CON_BOOT;
    - register_console(early_console);
    return 0;
    }

    diff --git a/kernel/printk.c b/kernel/printk.c
    index b4d97b5..45e0cec 100644
    --- a/kernel/printk.c
    +++ b/kernel/printk.c
    @@ -1129,6 +1129,28 @@ void console_start(struct console *console)
    }
    EXPORT_SYMBOL(console_start);

    +static int disable_boot_consoles(void)
    +{
    + struct console *bootconsole = console_drivers;
    + struct console *nextcon;
    + if (!bootconsole)
    + return 0;
    + while (bootconsole) {
    + nextcon = bootconsole->next;
    + if (bootconsole->flags & CON_BOOT) {
    + printk(KERN_INFO "turn off boot console %s%d\n",
    + console_drivers->name, console_drivers->index);
    + if (unregister_console(bootconsole) != 0)
    + printk(KERN_ERR "ERROR unregistering %s%d\n",
    + console_drivers->name,
    + console_drivers->index);
    + }
    + bootconsole = nextcon;
    + }
    + return 0;
    +}
    +late_initcall(disable_boot_consoles);
    +
    /*
    * The console driver calls this routine during kernel initialization
    * to register the console printing procedure with printk() and to
    @@ -1142,8 +1164,7 @@ void register_console(struct console *console)
    struct console *bootconsole = NULL;

    if (console_drivers) {
    - if (console->flags & CON_BOOT)
    - return;
    +
    if (console_drivers->flags & CON_BOOT)
    bootconsole = console_drivers;
    }
    @@ -1216,6 +1237,7 @@ void register_console(struct console *console)
    console->name, console->index);
    unregister_console(bootconsole);
    console->flags &= ~CON_PRINTBUFFER;
    + disable_boot_consoles();
    } else {
    printk(KERN_INFO "console [%s%d] enabled\n",
    console->name, console->index);
    @@ -1280,24 +1302,13 @@ int unregister_console(struct console *console)
    if (console_drivers != NULL && console->flags & CON_CONSDEV)
    console_drivers->flags |= CON_CONSDEV;

    + if (!res)
    + console->index = -1;
    release_console_sem();
    return res;
    }
    EXPORT_SYMBOL(unregister_console);

    -static int __init disable_boot_consoles(void)
    -{
    - if (console_drivers != NULL) {
    - if (console_drivers->flags & CON_BOOT) {
    - printk(KERN_INFO "turn off boot console %s%d\n",
    - console_drivers->name, console_drivers->index);
    - return unregister_console(console_drivers);
    - }
    - }
    - return 0;
    -}
    -late_initcall(disable_boot_consoles);
    -
    #if defined CONFIG_PRINTK

    /*
    --
    1.6.0.3.523.g304d0


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