If a device tree specified a preferred device for kernel console output
via the stdout-path or linux,stdout-path chosen node properties there's
no guarantee that it will have specified a device for which we have a
driver. It may also be the case that we do have a driver but it doesn't
call of_console_check() to register as a preferred console (eg. offb
driver as used on powermac systems). In these cases try to ensure that
we provide some console output by enabling the first console in the
console_drivers list.
As I don't have access to an affected system this has only been build
tested - testing would be most appreciated.
Signed-off-by: Paul Burton <paul.bur...@imgtec.com>
Fixes: 05fd007e4629 ("console: don't prefer first registered if DT specifies
stdout-path")
Reported-by: Andreas Schwab <sch...@linux-m68k.org>
Cc: Andreas Schwab <sch...@linux-m68k.org>
Cc: Andrew Morton <a...@linux-foundation.org>
Cc: Petr Mladek <pmla...@suse.com>
Cc: Sergey Senozhatsky <sergey.senozhat...@gmail.com>
Cc: Borislav Petkov <b...@suse.de>
Cc: Tejun Heo <t...@kernel.org>
Cc: linux-ker...@vger.kernel.org
Cc: linuxppc-dev@lists.ozlabs.org
---
A potential alternative to this might be to have the affected offb
driver call of_check_console(), and perhaps that should happen anyway,
but doing so seems non-trivial since the offb driver doesn't know the
index of the framebuffer console device it may be about to register &
the fbdev core doesn't know the associated device tree node. This also
wouldn't catch the case of us not having a driver for the device
specified by stdout-path, so this fallback seems worthwhile anyway.
---
kernel/printk/printk.c | 37 ++++++++++++++++++++++++++++++++++++-
1 file changed, 36 insertions(+), 1 deletion(-)
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index d5e3973..7091e2f 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -2835,10 +2835,45 @@ EXPORT_SYMBOL(unregister_console);
* intersects with the init section. Note that code exists elsewhere to get
* rid of the boot console as soon as the proper console shows up, so there
* won't be side-effects from postponing the removal.
+ *
+ * Additionally we may be using a device tree which specifies valid
+ * stdout-path referencing a device for which we don't have a driver, or for
+ * which we have a driver that doesn't register itself as preferred console
+ * using of_console_check(). In these cases we attempt here to enable the
+ * first registered console.
*/
static int __init printk_late_init(void)
{
- struct console *con;
+ struct console *con, *enabled;
+
+ if (of_specified_console) {
+ console_lock();
+
+ /* Find the enabled console, if there is one */
+ enabled = NULL;
+ for_each_console(con) {
+ if (!(con->flags & CON_ENABLED))
+ continue;
+
+ enabled = con;
+ break;
+ }
+
+ /* Enable the first console if none were already enabled */
+ con = console_drivers;
+ if (!enabled && con) {
+ if (con->index < 0)
+ con->index = 0;
+ if (con->setup == NULL ||
+ con->setup(con, NULL) == 0) {
+ con->flags |= CON_ENABLED;
+ if (con->device)
+ con->flags |= CON_CONSDEV;
+ }
+ }
+
+ console_unlock();
+ }
for_each_console(con) {
if (!keep_bootcon && con->flags & CON_BOOT) {
--
2.10.0
