core: Fix USB functionfs activation and clarify its documentation (#4188)

There was no certainty about how the path in service file should look
like for usb functionfs activation. Because of this it was treated
differently in different places, which made this feature unusable.

This patch fixes the path to be the *mount directory* of functionfs, not
ep0 file path and clarifies in the documentation that ListenUSBFunction should be
the location of functionfs mount point, not ep0 file itself.

diff --git a/man/systemd.socket.xml b/man/systemd.socket.xml
index 26e5d3c..5b6045f 100644 (file)
--- a/man/systemd.socket.xml
+++ b/man/systemd.socket.xml
@@ -294,10 +294,10 @@
         <term><varname>ListenUSBFunction=</varname></term>
         <listitem><para>Specifies a <ulink
         url="https://www.kernel.org/doc/Documentation/usb/functionfs.txt">USB
-        FunctionFS</ulink> endpoint location to listen on, for
+        FunctionFS</ulink> endpoints location to listen on, for
         implementation of USB gadget functions. This expects an
-        absolute file system path as the argument. Behavior otherwise
-        is very similar to the <varname>ListenFIFO=</varname>
+        absolute file system path of functionfs mount point as the argument.
+        Behavior otherwise is very similar to the <varname>ListenFIFO=</varname>
         directive above. Use this to open the FunctionFS endpoint
         <filename>ep0</filename>. When using this option, the
         activated service has to have the

diff --git a/src/core/socket.c b/src/core/socket.c
index 70d55dd..b9032fa 100644 (file)
--- a/src/core/socket.c
+++ b/src/core/socket.c
@@ -1334,14 +1334,9 @@ static int usbffs_select_ep(const struct dirent *d) {
 
 static int usbffs_dispatch_eps(SocketPort *p) {
         _cleanup_free_ struct dirent **ent = NULL;
-        _cleanup_free_ char *path = NULL;
         int r, i, n, k;
 
-        path = dirname_malloc(p->path);
-        if (!path)
-                return -ENOMEM;
-
-        r = scandir(path, &ent, usbffs_select_ep, alphasort);
+        r = scandir(p->path, &ent, usbffs_select_ep, alphasort);
         if (r < 0)
                 return -errno;
 
@@ -1356,7 +1351,7 @@ static int usbffs_dispatch_eps(SocketPort *p) {
         for (i = 0; i < n; ++i) {
                 _cleanup_free_ char *ep = NULL;
 
-                ep = path_make_absolute(ent[i]->d_name, path);
+                ep = path_make_absolute(ent[i]->d_name, p->path);
                 if (!ep)
                         return -ENOMEM;