Change a linux kernel config option from y to m, including its reverse dependencies

Question

I want to build phylink support (CONFIG_PHYLINK) as a module. In my config, some reverse dependencies of CONFIG_PHYLINK are configured as builtin (=y). Is there some tool that helps to switch all reverse dependencies to be build as a module, so CONFIG_PHYLINK can be set to =m?

• sawdust: Are you manually editing the .config file (a bad practice), or using make menuconfig (which is the "some tool" you seek)?
• Scorpi: CONFIG_PHYLINK has no prompt in menuconfig, it is selected by its reverse dependencies if one of them is enabled. Menuconfig is of some help as it shows which reverse dependencies are set to "=y". But I just have to manually change all of them to "=m", as well as further recursive reverse dependencies. I'd like to know if there is another tool with less manual steps.
• 0andriy: Maybe merge_config helps?
• Scorpi: Meanwhile I manually went through all reverse dendencies and changed them to "=m".

Answer 1

make menuconfig or make nconfig are designed to do this for you - personally I find the latter nicer and may do what you're after by first enabling "all entries" F4 before searching with F8

I don't immediately have an instance to see if there's a flip-tree, but you can at least find the dependency graph this way

With the keys you could flip them manually or do something ugly like this (lightly tested) to flip a collection of CONFIG_ keys outside the tool, but beware not all keys support m and I generally don't suggest doing this and instead giving each full name explicitly if you're producing your own script!

cp .config config.bak$(date --iso-8601=s)
cat <<EOF | xargs -I{} sed -iE "s/^\(CONFIG_{}=\)./1円m/" .config
put
your
keys
here
EOF

• Scorpi: Thanks, this is basically the "manual" method I also mentioned today.