Re: [PATCH 1/3] dummycon: only build module if there are users

[Thomas Zimmermann <tzimmermann@suse.de>]

Hi

Am 26.02.25 um 08:55 schrieb Arnd Bergmann:
> On Wed, Feb 26, 2025, at 08:48, Thomas Zimmermann wrote:
>> Am 25.02.25 um 17:44 schrieb Arnd Bergmann:
>>> From: Arnd Bergmann <arnd@arndb.de>
>>>
>>> Dummycon is used as a fallback conswitchp for vgacon and fbcon
>>> in the VT code, and there are no references to it if all three
>>> are disabled, so just leave it out of the kernel image for
>>> configurations without those.
>>>
>>> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
>>> ---
>>>    drivers/video/console/Kconfig | 3 +--
>>>    1 file changed, 1 insertion(+), 2 deletions(-)
>>>
>>> diff --git a/drivers/video/console/Kconfig b/drivers/video/console/Kconfig
>>> index bc31db6ef7d2..1c4263c164ce 100644
>>> --- a/drivers/video/console/Kconfig
>>> +++ b/drivers/video/console/Kconfig
>>> @@ -47,8 +47,7 @@ config SGI_NEWPORT_CONSOLE
>>>    	  card of your Indy.  Most people say Y here.
>>>    
>>>    config DUMMY_CONSOLE
>>> -	bool
>>> -	default y
>>> +	def_bool VT || VGA_CONSOLE || FRAMEBUFFER_CONSOLE
>> What about MDA_CONSOLE and STI_CONSOLE. Don't they require this as fallback?
>>
> MDA_CONSOLE clearly does not, because that is only the second
> console when VGA_CONSOLE is the main one.
>
> For sti_console, I don't see how it would do use it: when CONFIG_VT
> is enabled, the line above turns on DUMMY_CONSOLE, but without
> CONFIG_VT there seems to be no reference to it after
> 58a5c67aadde ("parisc/sticon: Always register sticon console
> driver"). I also see that CONFIG_STI_CONSOLE is a 'bool' symbol,
> so there is no dynamic loading/unloading of the driver.

Thanks.

Here's another general question. vgacon and fbcon only seem usable with 
CONFIG_VT=y. Wouldn't it make sense to have them depend on CONFIG_VT=y? 
dummycon could then be implemented as part of the vt code, maybe even 
become a vt-internal thing. The console code is complex, so I'm probably 
missing something here?

Best regards
Thomas

>
>      Arnd

-- 
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstrasse 146, 90461 Nuernberg, Germany
GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman
HRB 36809 (AG Nuernberg)