On 02/21/2018 05:39 PM, Farhan Ali wrote:

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

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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.

All right. This patch then makes sure that VT does not crash since it guarantees
that DUMMY_CONSOLE is available. If the user want to have virtio-gpu it needs to
enable PCI due to the dependencies, but this is a different issue that we can fix
later.
So the patch is fine as long as you take care of these things

- add missing HAS_IOMEM dependency to VGA_CONSOLE

- extend "if HAS_IOMEM" in drivers/video/Kconfig to cover config items
  previously covered by this dependency (it should start before config
  HAVE_FB_ATMEL and end after config HDMI)

as requested by Bartlomiej