linux-kernel - Re: [PATCH v3 1/3] Kconfig : Remove HAS_IOMEM dependency for Graphics support

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Date:   Wed, 21 Feb 2018 13:11:42 +0100
From:   Christian Borntraeger <borntraeger@...ibm.com>
To:     Cornelia Huck <cohuck@...hat.com>
Cc:     Thomas Huth <thuth@...hat.com>,
        Farhan Ali <alifm@...ux.vnet.ibm.com>,
        linux-kernel@...r.kernel.org, linux-s390@...r.kernel.org,
        linux-fbdev@...r.kernel.org, geert@...ux-m68k.org,
        tomi.valkeinen@...com, b.zolnierkie@...sung.com
Subject: Re: [PATCH v3 1/3] Kconfig : Remove HAS_IOMEM dependency for Graphics
 support



On 02/21/2018 01:07 PM, Cornelia Huck wrote:
[...]
>>> But if you need to enable PCI to get IOMEM, I wonder why this patch here
>>> is needed at all? The Graphics menu / VT dummy console should be
>>> available in the config if IOMEM is enabled anyway?  
>>
>> That is a good question. With CONFIG_PCI=y I can select virtio-gpu and dummy-console.
>> IIRC the issue was that with patch 3 we can have the situation where we have
>> CONFIG_VT = y and CONFIG_DUMMY_CONSOLE=n and this will crash early during boot as
>> conswitchp is NULL. 
> 
> So in practice, CONFIG_VT depends on "there's a console available, even
> if it's only the dummy one"?

Yes. Maybe we should simple move dummy_console outside of drivers/video/console/Kconfig
into something that is always available.

> 
>> This patches goal was to always enable dummy console even without
>> PCI, but it obviously fails to do so.
> 
> OTOH, the dummy console really should not depend on anything, as it is
> only doing dummy things.
> 
>>
>> So what about allowing CONFIG_VT on s390 only if we have PCI?
>>
>>
>> diff --git a/drivers/tty/Kconfig b/drivers/tty/Kconfig
>> index 84810075a6a0..1c7fe09d6f90 100644
>> --- a/drivers/tty/Kconfig
>> +++ b/drivers/tty/Kconfig
>> @@ -11,7 +11,7 @@ if TTY
>>  
>>  config VT
>>         bool "Virtual terminal" if EXPERT
>> -       depends on !UML
>> +       depends on !UML && (!S390 || PCI)
>>         select INPUT
>>         default y
>>         ---help---
>>
> 
> Would cover your use case, but feels wrong to me... config dependencies
> aren't fun :/
>