linux-kernel - Re: [PATCH] s390/console: enable dummy console for vt

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Message-Id: <b2615fca-2784-4f0a-2f21-7e7074c6760b@linux.vnet.ibm.com>
Date:   Mon, 19 Feb 2018 08:35:56 -0500
From:   Farhan Ali <alifm@...ux.vnet.ibm.com>
To:     Christian Borntraeger <borntraeger@...ibm.com>,
        Thomas Huth <thuth@...hat.com>,
        Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux Fbdev development list <linux-fbdev@...r.kernel.org>,
        linux-s390 <linux-s390@...r.kernel.org>,
        Stefan Kristiansson <stefan.kristiansson@...nalahti.fi>,
        Tomi Valkeinen <tomi.valkeinen@...com>,
        Martin Schwidefsky <schwidefsky@...ibm.com>,
        DRI Development <dri-devel@...ts.freedesktop.org>,
        Chen Liqin <liqin.linux@...il.com>,
        Lennox Wu <lennox.wu@...il.com>, Jeff Dike <jdike@...toit.com>,
        Richard Weinberger <richard@....at>,
        uml-devel <user-mode-linux-devel@...ts.sourceforge.net>
Subject: Re: [PATCH] s390/console: enable dummy console for vt



On 02/15/2018 07:02 AM, Christian Borntraeger wrote:
> 
> 
> On 02/15/2018 12:57 PM, Thomas Huth wrote:
>> On 15.02.2018 12:26, Geert Uytterhoeven wrote:
>>> Hi Christian,
>>>
>>> On Thu, Feb 15, 2018 at 12:14 PM, Christian Borntraeger
>>> <borntraeger@...ibm.com> wrote:
>>>> To enable the virtual terminal layer with virtio-gpu, we need to
>>>> provide the dummy console. This console is hidden behind CONFIG_IOMEM
>>>> via the graphics support. Instead of fully enabling the graphic
>>>> drivers lets just provide a Kconfig option for the dummy console.
>>>>
>>>> Signed-off-by: Christian Borntraeger <borntraeger@...ibm.com>
>>>> ---
>>>> New version: instead of moving around the graphic and console stuff,
>>>> let's just keep an s390 specific variant of CONFIG_DUMMY_CONSOLE
>>>>   arch/s390/Kconfig | 5 +++++
>>>>   1 file changed, 5 insertions(+)
>>>>
>>>> diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
>>>> index cbe1d978693a..a69690f616f3 100644
>>>> --- a/arch/s390/Kconfig
>>>> +++ b/arch/s390/Kconfig
>>>> @@ -952,6 +952,11 @@ config S390_HYPFS_FS
>>>>
>>>>   source "arch/s390/kvm/Kconfig"
>>>>
>>>> +config DUMMY_CONSOLE
>>>> +       bool
>>>> +       depends on VT
>>>> +       default y
>>>> +
>>>>   config S390_GUEST
>>>>          def_bool y
>>>>          prompt "s390 support for virtio devices"
>>>
>>> Really?
>>>
>>> You already have your own copy of HAS_IOMEM, which makes it hard for
>>> people to track which one applies where.
>>
>> I think I agree with Geert - let's better fix this in a proper way
>> instead of doing hacks like this. I guess there will be other
>> architectures in the future that might want to use the dummy console
>> without CONFIG_IOMEM, so fixing this in drivers/video/ instead sounds
>> better to me.
> 
> The question is, what is the proper fix?
> 

How about we only fence off sub menu items such as DRM or GPU or Fbdev, 
which actually uses io memory, in drivers/video/Kconfig? Similar to what 
Thomas suggested for moving the CONFIG_IOMEM dependency for fbdevs?