As per the in-line comment, this is where distros should configure it.
Not via kernel command line parameters.
As found by looking at the implementation, while exploring the cause of
a bug on the Raspberry Pi 4, it was found that `cma=` on the command
line parameters will overwrite the values a device tree will have
configured for a given platform.
With this, the more recent 5.4 vendor kernel boots just fine on the
Raspberry Pi 4 using our common configuration.
This includes setting up everything for the mainline Raspberry Pi 4
image.
In fact, the only difference left in the Raspberry Pi 4-specific image
is the kernel from the vendor.
Instead of treating the sddm config a wall of text that doesn't allow us
to override anything, turn it into an attribute set.
We dump `extraConfig` and instead introduce `settings` that is merged
with the module defaults to provide the final configuration.
There is some additional noise in here due to nixpkgs-fmt.
* nixos/xmonad: xmonad config w/ghc+xmessage
When the "config" option isn't set, we use xmonad-with-packages to
provide xmonad with runtime access to an isolated ghc, ensuring it can
recompile and exec a user's local config (e.g. $HOME/.xmonad/xmonad.hs)
regardless of which ghc (if any) is on PATH.
When the "config" option is set, however, we compile a configured xmonad
executable upfront (during nixos-rebuild), and prior to this commit, it
was not provided with runtime access to an isolated ghc.
As a result, with the "config" option set, it was not possible
to recompile and exec a user's local config unless there was a
compatible version of ghc on PATH with the necessary packages (xmonad,
xmonad-contrib, etc.) in its package database. Adding such a ghc to
environment.systemPackages, e.g.
(haskellPackages.ghcWithPackages (ps: with ps; [xmonad xmonad-contrib]))
is problematic because it adds both ghc and an unconfigured xmonad to
PATH, e.g.
$ ls -l $(which xmonad ghc)
lrwxrwxrwx ... /run/current-system/sw/bin/ghc -> /nix/store/...-ghc-8.10.2-with-packages/bin/ghc
lrwxrwxrwx ... /run/current-system/sw/bin/xmonad -> /nix/store/...-ghc-8.10.2-with-packages/bin/xmonad
Having the unconfigured xmonad on PATH is particularly bad because
restarting xmonad will dump the user into the unconfigured version, and
if no local config exists (e.g. in $HOME/.xmonad/xmonad.hs), they'll be
left in this unconfigured state.
In this commmit, we give the configured xmonad runtime access to ghc
like xmonad-with-packages does for the unconfigured version. The aim
is to allow the user to switch between the nixos module's config and a
local config (e.g. $HOME/.xmonad/xmonad.hs) at will, so they can try out
config changes without performing a nixos-rebuild.
Since the xmonad on PATH is the configured executable, there's no
danger a user could unwittingly restart into the unconfigured version,
and because xmonad will refuse to recompile when no local config
exists, there's no danger a user could unwittingly recompile into an
unconfigured version.
Given that a local config exists, the recompile/restart behavior depends
on two factors:
- which entry point is used
* 'XMonad.xmonad' (default)
* 'XMonad.launch' (recommended in "config" option description)
- what operation is triggered (i.e. via mod+q)
* `spawn "xmonad --recompile && xmonad --restart"` (default)
* `restart "xmonad" True`
* custom function
If the default 'XMonad.xmonad' entrypoint and default mod+q operation
are used, hitting mod+q will compile and exec the local config, which
will remain in use until next time the display manager is restarted.
If the entrypoint is changed to 'XMonad.launch' but mod+q left with its
default operation, hitting mod+q will have no visible effect. The logs
(as seen by running `journalctl --identifier xmonad --follow`) will show
an error,
X Error of failed request: BadAccess (attempt to access private resource denied)
which indicates that the shell was unable to start xmonad because
another window manager is already running (namely, the nixos-configured
xmonad).
https://wiki.haskell.org/Xmonad/Frequently_asked_questions#X_Error_of_failed_request:_BadAccess_.28attempt_to_access_private_resource_denied.29
Changing the mod+q operation to `restart "xmonad" True` (as recommended
in the "config" option's description) will allow a restart of the
nixos-configured xmonad to be triggeredy by hitting mod+q.
Finally, if the entrypoint is 'XMonad.launch', mod+q has been
bound to `restart "xmonad" True` and another key bound to a custom
recompile/restart function (e.g. `compileRestart` as shown in the
"config" option example), the user can switch between the nixos module's
config and their local config, with the custom key switching to the
local config and mod+q switching back.
* nixos/xmonad: refactor let binding
* nixos/xmonad: refactor (eliminate duplicate code)
* nixos/xmonad: install man pages
Prior to this commit, man pages were not installed if the "config"
option was set.
* nixos/xmonad: comment grammar fixups
* nixos/xmonad: writeStateToFile in example config
Calling writeStateToFile prior to recompiling and restarting allows
state (workspaces, etc.) to be preserved across the restart.
* nixos/xmonad: add ivanbrennan to maintainers
* nixos/xmonad: adjust compileRestart example
* nixos/xmonad: add missing import to example config
@poettering decided we only need a limited number of inodes in our /tmp,
so why not limit that for every systemd user? That makes medium-sized nix
builds impossible so this commit restores the old behaviour which is the
kernel default of half the number of physical RAM pages which does not
seem too unreasonable to me.
