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 :/ >>
WARNING: multiple messages have this Message-ID (diff)
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 16:39:12 +0000 [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: 49+ 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 ` Farhan Ali 2018-02-19 15:47 ` [PATCH v3 1/3] Kconfig : Remove HAS_IOMEM dependency for Graphics support Farhan Ali 2018-02-19 15:47 ` Farhan Ali 2018-02-19 16:25 ` Thomas Huth 2018-02-19 16:25 ` Thomas Huth 2018-02-19 16:38 ` Farhan Ali 2018-02-19 16:38 ` Farhan Ali 2018-02-21 10:05 ` Christian Borntraeger 2018-02-21 10:05 ` Christian Borntraeger 2018-02-21 10:22 ` Christian Borntraeger 2018-02-21 10:22 ` Christian Borntraeger 2018-02-21 10:32 ` Cornelia Huck 2018-02-21 10:32 ` Cornelia Huck 2018-02-21 11:09 ` Christian Borntraeger 2018-02-21 11:09 ` Christian Borntraeger 2018-02-21 11:14 ` Thomas Huth 2018-02-21 11:14 ` Thomas Huth 2018-02-21 11:22 ` Christian Borntraeger 2018-02-21 11:22 ` Christian Borntraeger 2018-02-21 11:29 ` Thomas Huth 2018-02-21 11:29 ` Thomas Huth 2018-02-21 11:49 ` Christian Borntraeger 2018-02-21 11:49 ` Christian Borntraeger 2018-02-21 12:07 ` Cornelia Huck 2018-02-21 12:07 ` Cornelia Huck 2018-02-21 12:11 ` Christian Borntraeger 2018-02-21 12:11 ` Christian Borntraeger 2018-02-21 16:39 ` Farhan Ali [this message] 2018-02-21 16:39 ` Farhan Ali 2018-02-22 7:34 ` Christian Borntraeger 2018-02-22 7:34 ` Christian Borntraeger 2018-02-21 11:23 ` Cornelia Huck 2018-02-21 11:23 ` Cornelia Huck 2018-02-21 8:44 ` Christian Borntraeger 2018-02-21 8:44 ` Christian Borntraeger 2018-02-21 11:50 ` Bartlomiej Zolnierkiewicz 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 15:47 ` Farhan Ali 2018-02-19 19:52 ` Thomas Huth 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 15:47 ` Farhan Ali 2018-02-19 19:55 ` Thomas Huth 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 9:43 ` Christian Borntraeger 2018-02-20 13:45 ` Farhan Ali
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