[elrepo] How to understand elrepo kernel config changes

[Chengwei Yang]

On Fri, Aug/02/2019 at 20:50:12 +0100, Phil Perry wrote:
> On 02/08/2019 07:58, Chengwei Yang wrote:
> > Hi there,
> > 
> > I'm new to elrepo and I found that the goal of elrepo is exactly the same as me.
> > 
> > I checked kernel-lt and found that it brings a config file which I curious a lot
> > how to understand what it does, because I found there are a lot of changes from
> > centos 3.10.0 kernel config.
> > 
> > I did below to check config changes:
> > 
> > ```
> > [root at linux-4.4.186]# cp /boot/config-3.10.0-693.21.1.el7.x86_64 .config
> > [root at linux-4.4.186]# make -s ARCH=x86_64 listnewconfig | wc -l
> > .config:3082:warning: symbol value 'm' invalid for PINCTRL_AMD
> > 506
> > ```
> > 
> > so there are 506 new changes.
> > 
> > I make all new changes as default configs.
> > 
> > ```
> > [root at linux-4.4.186]# make -s ARCH=x86_64 alldefconfig
> > [root at linux-4.4.186]# make -s ARCH=x86_64 listnewconfig |wc -l
> > 0
> > ```
> > 
> > and then check the diff.
> > 
> > ```
> > [root at linux-4.4.186]# diff -u .config config-4.4.186-x86_64 |wc -l
> > 7712
> > ```
> > 
> > There are a lot of changes from default configs, please help me to understand
> > what config-4.4.186-x86_64 changes.
> > 
> 
> I guess I should explain the history of how we ended up where we are today
> with the config file.
> 
> The config file started it's life around the time of kernel-3.14. The
> current RHEL el7 kernel config was taken as a starting point and all new
> options were reviewed and set on a case by case basis to generate an initial
> release candidate. A lot of testing and further release candidates followed
> and ultimately culminated in the release of a 3.15.0 kernel as the first el7
> 'GA' release.
> 
> For every subsequent new source code release, any new configuration options
> were again considered on a case by case basis. If the new option was part of
> a pre-existing option that was already enabled, then the new option would
> generally be enabled also.
> 
> Along the way many users have requested options be enabled within the
> kernel. These requests have generally been actioned unless deemed to be
> detrimental or otherwise not advisable. (Such requests should be made as
> RFEs's against the appropriate kernel package on elrepo.org/bugs otherwise
> they will be ignored).
> 
> The above process originally started out it's life as kernel-ml and then
> back in March 2016 forked to become kernel-lt with the release of
> kernel-lt-4.4.6.
> 
> The above process has been meticulously documented within the package
> changelog, which you can inspect in the (S)RPM or here:
> 
> https://github.com/elrepo/packages/blob/master/kernel-lt/el7/kernel-lt-4.4.spec
> 
> To understand the changes, you will need to individually review each in
> turn, reading the documentation for each as Alan has done over the last 5+
> years when making those decisions.
> 
> Hope that helps.

Thank Phil for your great patients, it did answered my question and the
changelog is helpful.

> 
> Phil
> 
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-- 
Thanks,
Chengwei