flipper-bls.sh: per-profile user DT overlay drop-ins

Apply every *.dtbo a user drops in a profile's /etc/kernel/dtbo/ to that
profile's BLS entries. emit_entry merges them (subvol-prefixed, after the
profile-declared overlays) into the devicetree-overlay line; flipper_write_entry
scans the target root so clones pick up their own. Silent when the dir is empty.

Author: Yury-MonZon

overlays/usr/lib/flipper-bls.sh

@@ -212,6 +212,22 @@ overlay_paths() {  # $1 = subvol prefix (e.g. /@Desktop); remaining args = overl
     printf '%s' "$_paths"
 }
 
+# Per-profile user drop-in overlays: every *.dtbo under this root's /etc/kernel/dtbo, applied to
+# each of the profile's entries. OVERLAY_USER_DIR is the on-disk scan dir (default CONF_ROOT/dtbo,
+# i.e. the booted profile; flipper_write_entry points it at the target root). The in-entry path is
+# subvol-prefixed like devicetreedir. Silent no-op when the dir is absent or empty.
+OVERLAY_USER_REL=/etc/kernel/dtbo
+user_overlay_paths() {  # $1 = subvol prefix (e.g. /@Desktop)
+    _udir="${OVERLAY_USER_DIR:-$CONF_ROOT/dtbo}"
+    [ -d "$_udir" ] || return 0
+    _upaths=""
+    for _uf in "$_udir"/*.dtbo; do
+        [ -f "$_uf" ] || continue                     # unmatched glob -> skip
+        _upaths="$_upaths${_upaths:+ }$1$OVERLAY_USER_REL/${_uf##*/}"
+    done
+    printf '%s' "$_upaths"
+}
+
 # Set BASE_OPTS from CONF_ROOT/cmdline (root=UUID + policy) + this kernel's console layout.
 # FIQ kernel -> console=ttyFIQ0 ; mainline -> console=ttyS0 + ttyS4 + fbcon=map:1.
 compute_base_opts() {
@@ -281,9 +297,10 @@ emit_entry() {
     _opts="$BASE_OPTS"
     [ -n "$_extra" ] && _opts="$_opts $_extra"
     _fn="$ENTRIES/$ENTRY_TOKEN-$KERNEL_VERSION.conf"
+    _user="$(user_overlay_paths "$(fdt_prefix "$_opts")")"   # user drop-ins, always optional
 
     if [ -z "$_dtbos" ]; then
-        write_entry "$_fn" "$(make_title "$_suf")" "$_opts" ""
+        write_entry "$_fn" "$(make_title "$_suf")" "$_opts" "$_user"
         return 0
     fi
 
@@ -297,7 +314,8 @@ emit_entry() {
         log "skip $ENTRY_TOKEN (overlays not found for $KERNEL_VERSION)"
         return 0
     fi
-    write_entry "$_fn" "$(make_title "$_suf")" "$_opts" "$_paths"
+    # profile overlays first, then the user's drop-ins layered on top
+    write_entry "$_fn" "$(make_title "$_suf")" "$_opts" "$_paths${_paths:+${_user:+ }}$_user"
 }
 
 # flipper_write_entry <subvol> <mounted-path> [<origin-hint>]: write a BLS entry for an EXISTING
@@ -325,6 +343,7 @@ flipper_write_entry() {
     # devicetreedir is the target root's OWN kernel dir (KERNEL_VERSION came from it, so it exists).
     DEVICETREEDIR_REL="/usr/lib/linux-image-$KERNEL_VERSION"
     OVERLAY_DIR="$DTB_DIR/$VENDOR"
+    OVERLAY_USER_DIR="$_snap/etc/kernel/dtbo"   # scan the TARGET root's drop-ins, not the running one
     # pin the root's own entry-token so a later runtime apt install in it lands in the same band
     mkdir -p "$_snap/etc/kernel" && printf '%s\n' "$ENTRY_TOKEN" > "$_snap/etc/kernel/entry-token"
     emit_entry "$(printf '%s' "$_name" | tr -d '@')" "rootflags=subvol=$_name" "" ""