[3/5] initdev:kernel: Await console discovery, v5

The patch has been re-written to use the init device synchronization
infrastructure. This ensures that we can detect console initialization when
the devices become available, as well as determining that no console is
attached at boot time.

History
v5	Change bootdev_* to initdev_*.
v4	Use new hotplug synchronization infrastructure. Include Braille
	console support.
v3.2	Use only a single new command line parameter by adding the possible
	value "forever".  Add message specifying the parameter to modify to
	increase the delay for console initialization
v3.1	Correct the abbreviation for milliseconds in
	Documentation/kernel-parameters.txt to be "ms", not "mS". Thanks to
	Peter Anvin for this.
v3	Increase the default delay to 1 second and add kernel command line
	parameters to override the default delay. Thanks to David Brownell for
	his helpful suggestions.
v2	Wait for the preferred console rather than any console. Make the
	delay interval a tunable.
v1	Initial version

Signed-off-by: David VomLehn <dvomlehn@cisco.com>
---
 drivers/accessibility/braille/braille_console.c |    3 ++
 kernel/printk.c                                 |   29 ++++++++++++++++++++++-
 2 files changed, 31 insertions(+), 1 deletions(-)

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On Fri, 1 May 2009 19:27:56 -0700
David VomLehn <dvomlehn@cisco.com> wrote:

> The patch has been re-written to use the init device synchronization
> infrastructure. This ensures that we can detect console
> initialization when the devices become available, as well as
> determining that no console is attached at boot time.
> 
> History
> v5	Change bootdev_* to initdev_*.
> v4	Use new hotplug synchronization infrastructure. Include
> Braille console support.
> v3.2	Use only a single new command line parameter by adding
> the possible value "forever".  Add message specifying the parameter
> to modify to increase the delay for console initialization
> v3.1	Correct the abbreviation for milliseconds in
> 	Documentation/kernel-parameters.txt to be "ms", not "mS".
> Thanks to Peter Anvin for this.
> v3	Increase the default delay to 1 second and add kernel
> command line parameters to override the default delay. Thanks to
> David Brownell for his helpful suggestions.
> v2	Wait for the preferred console rather than any console.
> Make the delay interval a tunable.
> v1	Initial version
> 
> Signed-off-by: David VomLehn <dvomlehn@cisco.com>
> ---
>  drivers/accessibility/braille/braille_console.c |    3 ++
>  kernel/printk.c                                 |   29
> ++++++++++++++++++++++- 2 files changed, 31 insertions(+), 1
> deletions(-)
> 
> diff --git a/drivers/accessibility/braille/braille_console.c
> b/drivers/accessibility/braille/braille_console.c index
> d672cfe..4420ac3 100644 ---
> a/drivers/accessibility/braille/braille_console.c +++
> b/drivers/accessibility/braille/braille_console.c @@ -35,6 +35,7 @@
>  #include <linux/keyboard.h>
>  #include <linux/kbd_kern.h>
>  #include <linux/input.h>
> +#include <linux/initdev.h>
>  
>  MODULE_AUTHOR("samuel.thibault@ens-lyon.org");
>  MODULE_DESCRIPTION("braille device");
> @@ -378,6 +379,8 @@ int braille_register_console(struct console
> *console, int index, braille_co = console;
>  	register_keyboard_notifier(&keyboard_notifier_block);
>  	register_vt_notifier(&vt_notifier_block);
> +
> +	initdev_register(BOOTDEV_CONSOLE);

Should it be initdev_registered(BOOTDEV_CONSOLE)?


>  	return 0;
>  }
>  
> diff --git a/kernel/printk.c b/kernel/printk.c
> index 5052b54..e6a9379 100644
> --- a/kernel/printk.c
> +++ b/kernel/printk.c
> @@ -33,6 +33,7 @@
>  #include <linux/bootmem.h>
>  #include <linux/syscalls.h>
>  #include <linux/kexec.h>
> +#include <linux/device.h>
>  
>  #include <asm/uaccess.h>
>  
> @@ -1075,8 +1076,10 @@ void console_unblank(void)
>  
>  /*
>   * Return the console tty driver structure and its associated index
> + * @index:	Pointer to the device index
> + * Returns NULL if no driver available, otherwise a pointer to the
> TTY driver. */
> -struct tty_driver *console_device(int *index)
> +struct tty_driver *_console_device(int *index)
>  {
>  	struct console *c;
>  	struct tty_driver *driver = NULL;
> @@ -1094,6 +1097,29 @@ struct tty_driver *console_device(int *index)
>  }
>  
>  /*
> + * Returns true if all specific consoles are registered, false
> otherwise
> + */
> +static bool have_all_consoles(void)
> +{
> +	struct tty_driver *driver;
> +	int		index;
> +
> +	driver = _console_device(&index);
> +
> +	return driver != NULL;
> +}
> +
> +struct tty_driver *console_device(int *index)
> +{
> +	struct tty_driver *driver;
> +	initdev_wait(BOOTDEV_CONSOLE, have_all_consoles);
> +
> +	driver = _console_device(index);
> +
> +	return driver;
> +}
> +
> +/*
>   * Prevent further output on the passed console device so that (for
> example)
>   * serial drivers can disable console output before suspending a
> port, and can
>   * re-enable output afterwards.
> @@ -1230,6 +1256,7 @@ void register_console(struct console *console)
>  		spin_unlock_irqrestore(&logbuf_lock, flags);
>  	}
>  	release_console_sem();
> +	initdev_registered(BOOTDEV_CONSOLE);
>  }
>  EXPORT_SYMBOL(register_console);
>  
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On Fri, May 01, 2009 at 11:38:25PM -0400, Ming Lei wrote:
> On Fri, 1 May 2009 19:27:56 -0700
> David VomLehn <dvomlehn@cisco.com> wrote:
...
> > diff --git a/drivers/accessibility/braille/braille_console.c
> > b/drivers/accessibility/braille/braille_console.c index
> > d672cfe..4420ac3 100644 ---
> > +
> > +	initdev_register(BOOTDEV_CONSOLE);
> 
> Should it be initdev_registered(BOOTDEV_CONSOLE)?

Yes.

> Lei Ming

Thanks!

David VomLehn
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