vconsole-setup: downgrade log message when setting font fails on dummy console

Since commit 883eb9be985fd86d9cabe967eeeab91cdd396a81, vconsole-setup might be
called again to operate on dummy console where font operations are not
supported but where it's still important to have the correct keymap set [0][1].

vconsole-setup is mainly called by udev but can also be run via a dependency of
an early service. Both cases might end up calling vconsole-setup on the dummy
console.

The first case can happen during early boot even on systems that use (instead
of the dummy console) a "simple" video console driver supporting font
operations (such as vgacon) until a more specific driver (such as i915) takes
the console over. While this is happening vgacon is deactivated and temporarly
replaced by the dummy console [2].

There are also other cases where systemd-vconsole-setup might be called on
dummy console especially during (very) early boot. Indeed
systemd-vconsole-setup.service might be pulled in by early interactive services
such as 'dracut-cmdline-ask.service` which is run before udev.

If that happens on platforms with no grapical HWs (such as embedded ARM) or
with dummy console initially installed until a driver takes over (like Xen and
xen-fbfront) then setting font will fail.

Therefore this patch downgrades the log message emitted when setting font fails
to LOG_DEBUG and when font operations is not implemented like it's the case for
the dummy console.

Fixes: #16406.

[0] https://github.com/systemd/systemd/issues/10826
[1] https://bugzilla.redhat.com/show_bug.cgi?id=1652473
[2] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/gpu/vga/vgaarb.c?h=v5.7#n204

1 files changed, 14 insertions, 4 deletions

diff --git a/src/vconsole/vconsole-setup.c b/src/vconsole/vconsole-setup.c
index 9d706085fb..a2fe7e9099 100644
--- a/src/vconsole/vconsole-setup.c
+++ b/src/vconsole/vconsole-setup.c
@@ -226,6 +226,7 @@ static void setup_remaining_vcs(int src_fd, unsigned src_idx, bool utf8) {
         _cleanup_free_ struct unipair* unipairs = NULL;
         _cleanup_free_ void *fontbuf = NULL;
         unsigned i;
+        int log_level;
         int r;
 
         unipairs = new(struct unipair, USHRT_MAX);
@@ -234,11 +235,20 @@ static void setup_remaining_vcs(int src_fd, unsigned src_idx, bool utf8) {
                 return;
         }
 
+        log_level = LOG_WARNING;
+
         /* get metadata of the current font (width, height, count) */
         r = ioctl(src_fd, KDFONTOP, &cfo);
-        if (r < 0)
-                log_warning_errno(errno, "KD_FONT_OP_GET failed while trying to get the font metadata: %m");
-        else {
+        if (r < 0) {
+                /* We might be called to operate on the dummy console (to setup keymap
+                 * mainly) when fbcon deferred takeover is used for example. In such case,
+                 * setting font is not supported and is expected to fail. */
+                if (errno == ENOSYS)
+                        log_level = LOG_DEBUG;
+
+                log_full_errno(log_level, errno,
+                               "KD_FONT_OP_GET failed while trying to get the font metadata: %m");
+        } else {
                 /* verify parameter sanity first */
                 if (cfo.width > 32 || cfo.height > 32 || cfo.charcount > 512)
                         log_warning("Invalid font metadata - width: %u (max 32), height: %u (max 32), count: %u (max 512)",
@@ -273,7 +283,7 @@ static void setup_remaining_vcs(int src_fd, unsigned src_idx, bool utf8) {
         }
 
         if (cfo.op != KD_FONT_OP_SET)
-                log_warning("Fonts will not be copied to remaining consoles");
+                log_full(log_level, "Fonts will not be copied to remaining consoles");
 
         for (i = 1; i <= 63; i++) {
                 char ttyname[sizeof("/dev/tty63")];