From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christian Borntraeger Date: Thu, 22 Feb 2018 07:34:13 +0000 Subject: Re: [PATCH v3 1/3] Kconfig : Remove HAS_IOMEM dependency for Graphics support Message-Id: <2af46f6f-d225-9802-c6f9-98099fb2c2c8@de.ibm.com> List-Id: References: <2beec7645bac82e7bdef4f6df0b9f4fe28696575.1519053920.git.alifm@linux.vnet.ibm.com> <6cae85dc-76d5-1b92-ab13-a5e441eb84a0@linux.vnet.ibm.com> <20180221113217.11bb1c69.cohuck@redhat.com> <1f8907d4-c4a3-d41b-8834-679dcc85de4a@de.ibm.com> <5dfa9213-0e63-54d0-8700-1ced4efd4c28@redhat.com> <20180221130755.17d15f89.cohuck@redhat.com> <6c1daae4-e1f6-5627-9023-f03d986c5639@de.ibm.com> <2170dce6-4456-3ab6-d07c-2169d99c4173@linux.vnet.ibm.com> In-Reply-To: <2170dce6-4456-3ab6-d07c-2169d99c4173@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Farhan Ali , Cornelia Huck Cc: Thomas Huth , 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 On 02/21/2018 05:39 PM, Farhan Ali wrote: > > > 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. 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