On 02/21/2018 07:11 AM, Christian Borntraeger wrote:

On 02/21/2018 01:07 PM, Cornelia Huck wrote:
[...]

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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.

Yes, VT layer initializes very early in the boot process and looks for a 
console. If it can't find any it will crash. I believe that was the 
whole point of having the dummy console.

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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.

I agree, but where should it go? consoles are kinda tightly tied to 
video/Graphics Support.

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This patches goal was to always enable dummy console even without
PCI, but it obviously fails to do so.

This patch should enable the dummy console even without PCI but we won't 
have DRM/Virtio GPU.

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OTOH, the dummy console really should not depend on anything, as it is
only doing dummy things.

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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 :/