On 2016-01-15 13:25, Vineet Gupta wrote: > +CC Thomas, Peter > > On Friday 15 January 2016 04:19 PM, Alexey Brodkin wrote: >> Hi Felix, >> >> On Fri, 2016-01-15 at 11:45 +0100, Felix Fietkau wrote: >>> On 2016-01-15 00:12, Alexey Brodkin wrote: >>>> Given those patches are relevant to any ARC platform and even >>>> ISA version it makes perfect sense for patches to exist >>>> in one place instead of being duplicated for each new ARC-based ASIC. >>>> >>>> Note this is a prerequisite for upstreaming of ARC HS38 support in >>>> OpenWRT. >>>> >>>> Signed-off-by: Alexey Brodkin <abrodkin at synopsys.com> >>>> Cc: Felix Fietkau <nbd at openwrt.org> >>>> Cc: Jo-Philipp Wich <jow at openwrt.org> >>>> Cc: Jonas Gorski <jogo at openwrt.org> >>>> --- /dev/null >>>> +++ b/target/linux/generic/patches-4.4/331-arc-remove-dependency-on-DEVTMPFS.patch >>>> @@ -0,0 +1,36 @@ >>>> +From adfbf9e6cad93281cffceab078e7f6f2a8e094f9 Mon Sep 17 00:00:00 2001 >>>> +From: Alexey Brodkin <abrodkin at synopsys.com> >>>> +Date: Thu, 13 Aug 2015 01:56:02 +0300 >>>> +Subject: [PATCH 1/2] openwrt: arc - remove dependency on DEVTMPFS >>>> + >>>> +OpenWRT builds initramfs so that it doesn't require DEVTMPFS so dropping >>>> +this dependency. > > Really ? AFAIKR (circa 2012) DEVTMPFS was *needed* for dynamic device nodes and > that included the common case of initramfs NOT having static device nodes. > > So back then I added the code in question to kernel Kconfig because initramfs was > my primary workflow and occassionally I would fail to include DEVTMPFS causing > userspace boot to go bonkers (FWIW I was using the buildroot trick of a pre-init > script which would automount devtmpfs before exec'ing the real init) > > Now arguably I can add DEVTMPFS to defconfigs, but then we don't need the kconfig > dependency framework at all. > > Another idea is to add DEVTMPFS unconditionally to Kconfig, but I fail to remember > why I didn't do it at the time. Does anyone know if it interferes with real rootfs > backed by real devices ? OpenWrt works just fine without DEVTMPFS - doesn't matter if initramfs is enabled or not. I also don't think there's anything architecture specific about requiring DEVTMPFS or not, so I'd say it doesn't make any sense to select it from arch/arc/Kconfig. >>>> That helps to escape 2 separate kernel rebuilds with >>>> +and without initramfs. >>>> + >>>> +2 builds happen because OpenWRT first builds kernel and later modules. >>>> +When building entire kernel with simple "make" INITRAMFS sets to a real >>>> +value and so was triggering DEVTMPFS selection. Then when building only >>>> +modules with "make modules" command INITRAMFS is zeroed and so kernel >>>> +config was changing that lead to full kernel rebuild. > > Just curious, why does make module zero out INITRAMFS - to save a bit of build time ? OpenWrt builds both initramfs and non-initramfs images, so it resets the INITRAMFS config item when it generates the kernel config for the first time. - Felix
