# Standalone daemon (`mtp-mountd`): auto-mount MTP devices on hotplug, for every app

[LinuxBoy-96]

TL;DR: mtp-mount's FUSE layer already makes cp/rsync/everything work over MTP. Proposal: split the mount logic into a library crate, and add a small daemon binary that auto-mounts devices on hotplug. Result: working MTP for the entire Linux desktop, no glib, no gvfs.

Why

gvfs is how desktops do MTP today, and its FUSE layer refuses plain writes:

POSIX write:        open() → write() → write() → close()
                     └ size unknown here
MTP protocol:       SendObjectInfo(size) → SendObject
                     └ size REQUIRED here
gvfs FUSE answer:   EOPNOTSUPP
mtp-mount answer:   spool locally, upload on close()  ✅

Users hit this constantly (cp: operation not supported threads go back 20 years; COSMIC alone has a dozen open issues on it — cross-ref: https://github.com/pop-os/cosmic-files/issues/1926 mtp-mount already has the right answer. It's just manual and single-device today.

What

Two crates in this workspace:

mtp-mount-core — the existing mount logic (inodes, sparse read cache, write spool, safe overwrites) extracted as a library. The current CLI becomes a thin consumer; its UX doesn't change.

mtp-mountd — a small systemd --user service on top:

1. Watch USB hotplug (nusb has this). Device appears → mount at $XDG_RUNTIME_DIR/mtp/<serial>/. Device unplugged → clean unmount.
2. One session + one mount per device, concurrently.
3. Announce mounts so desktops can show the device. v1 can be just the predictable directory (inotify-watchable) — near zero new code. D-Bus can come later.
4. Ship the unit file, log to journal.

Steps 1–2 are extensions of existing code. Step 3 v1 is almost free. The real new work is the crate split and service hardening.

Open questions

• Announcements v1: directory-only, socket, or D-Bus?
• Devices with multiple storages: one mount each, or subdirs under one mount?
• gvfs running on the same machine: document masking gvfs-mtp-volume-monitor, or detect-and-warn?

Who benefits

Every app that opens files: file managers (COSMIC is a good candidate— see cross-ref), rsync, editors, previewers, terminals. Any desktop, any distro.