From: Farhan Ali <alifm@linux.vnet.ibm.com>
To: Christian Borntraeger <borntraeger@de.ibm.com>,
Cornelia Huck <cohuck@redhat.com>
Cc: Thomas Huth <thuth@redhat.com>,
linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org,
linux-fbdev@vger.kernel.org, geert@linux-m68k.org,
tomi.valkeinen@ti.com, b.zolnierkie@samsung.com
Subject: Re: [PATCH v3 1/3] Kconfig : Remove HAS_IOMEM dependency for Graphics support
Date: Wed, 21 Feb 2018 11:39:12 -0500 [thread overview]
Message-ID: <2170dce6-4456-3ab6-d07c-2169d99c4173@linux.vnet.ibm.com> (raw)
In-Reply-To: <6c1daae4-e1f6-5627-9023-f03d986c5639@de.ibm.com>
On 02/21/2018 07:11 AM, Christian Borntraeger wrote:
>
>
> 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.
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.
>>
>> 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.
>>
>>> 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.
>> 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 :/
>>
next prev parent reply other threads:[~2018-02-21 16:39 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-02-19 15:47 [PATCH v3 0/3] Enable CONFIG_VT support for S390 Farhan Ali
2018-02-19 15:47 ` [PATCH v3 1/3] Kconfig : Remove HAS_IOMEM dependency for Graphics support Farhan Ali
2018-02-19 16:25 ` Thomas Huth
2018-02-19 16:38 ` Farhan Ali
2018-02-21 10:05 ` Christian Borntraeger
2018-02-21 10:22 ` Christian Borntraeger
2018-02-21 10:32 ` Cornelia Huck
2018-02-21 11:09 ` Christian Borntraeger
2018-02-21 11:14 ` Thomas Huth
2018-02-21 11:22 ` Christian Borntraeger
2018-02-21 11:29 ` Thomas Huth
2018-02-21 11:49 ` Christian Borntraeger
2018-02-21 12:07 ` Cornelia Huck
2018-02-21 12:11 ` Christian Borntraeger
2018-02-21 16:39 ` Farhan Ali [this message]
2018-02-22 7:34 ` Christian Borntraeger
2018-02-21 11:23 ` Cornelia Huck
2018-02-21 8:44 ` Christian Borntraeger
2018-02-21 11:50 ` Bartlomiej Zolnierkiewicz
2018-02-19 15:47 ` [PATCH v3 2/3] s390/char : Rename EBCDIC keymap variables Farhan Ali
2018-02-19 19:52 ` Thomas Huth
2018-02-19 15:47 ` [PATCH v3 3/3] s390/setup : enable display support for KVM guest Farhan Ali
2018-02-19 19:55 ` Thomas Huth
2018-02-20 9:43 ` [PATCH v3 0/3] Enable CONFIG_VT support for S390 Christian Borntraeger
2018-02-20 13:45 ` Farhan Ali
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