[PATCH 3.2 181/200] TTY: pmac_zilog, check existence of ports in pmz_console_init()

[Ben Hutchings]

3.2.56-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>

commit dc1dc2f8a5dd863bf2e79f338fc3ae29e99c683a upstream.

When booting a multi-platform m68k kernel on a non-Mac with "console=ttyS0"
on the kernel command line, it crashes with:

Unable to handle kernel NULL pointer dereference at virtual address   (null)
Oops: 00000000
PC: [<0013ad28>] __pmz_startup+0x32/0x2a0
...
Call Trace: [<002c5d3e>] pmz_console_setup+0x64/0xe4

The normal tty driver doesn't crash, because init_pmz() checks
pmz_ports_count again after calling pmz_probe().

In the serial console initialization path, pmz_console_init() doesn't do
this, causing the driver to crash later.

Add a check for pmz_ports_count to fix this.

Signed-off-by: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>
Cc: Finn Thain <fthain@xxxxxxxxxxxxxxxxxxx>
Cc: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 drivers/tty/serial/pmac_zilog.c | 3 +++
 1 file changed, 3 insertions(+)

--- a/drivers/tty/serial/pmac_zilog.c
+++ b/drivers/tty/serial/pmac_zilog.c
@@ -2198,6 +2198,9 @@ static int __init pmz_console_init(void)
 	/* Probe ports */
 	pmz_probe();
 
+	if (pmz_ports_count == 0)
+		return -ENODEV;
+
 	/* TODO: Autoprobe console based on OF */
 	/* pmz_console.index = i; */
 	register_console(&pmz_console);

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