[POWERPC] Optionally use new device number for pmac_zilog

This adds the option for the pmac_zilog driver to use the major/minor
numbers recently allocated specifically for it (/dev/ttyPZn) instead
of the /dev/ttySn numbers.  The advantage of doing this is that it
allows the pmac_zilog and 8250 drivers to coexist.  The disadvantage
of doing this is that it is a user-visible ABI change and it will
break existing working setups on powermacs, and could be confusing to
users.

Signed-off-by: David Woodhouse <dwmw2@infradead.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>

1 files changed, 25 insertions, 0 deletions

diff --git a/drivers/serial/Kconfig b/drivers/serial/Kconfig
index 81b52b7cca21..d6ae38e55d01 100644
--- a/drivers/serial/Kconfig
+++ b/drivers/serial/Kconfig
@@ -986,6 +986,31 @@ config SERIAL_PMACZILOG
           PowerMac machines.
           Say Y or M if you want to be able to these serial ports.
 
+config SERIAL_PMACZILOG_TTYS
+        bool "Use ttySn device nodes for Zilog z85c30"
+        depends on SERIAL_PMACZILOG
+        help
+          The pmac_zilog driver for the z85C30 chip on many powermacs
+          historically used the device numbers for /dev/ttySn.  The
+          8250 serial port driver also uses these numbers, which means
+          the two drivers being unable to coexist; you could not use
+          both z85C30 and 8250 type ports at the same time.
+
+          If this option is not selected, the pmac_zilog driver will
+          use the device numbers allocated for /dev/ttyPZn.  This allows
+          the pmac_zilog and 8250 drivers to co-exist, but may cause
+          existing userspace setups to break.  Programs that need to
+          access the built-in serial ports on powermacs will need to
+          be reconfigured to use /dev/ttyPZn instead of /dev/ttySn.
+
+          If you enable this option, any z85c30 ports in the system will
+          be registered as ttyS0 onwards as in the past, and you will be
+          unable to use the 8250 module for PCMCIA or other 16C550-style
+          UARTs.
+
+          Say N unless you need the z85c30 ports on your powermac
+          to appear as /dev/ttySn.
+
 config SERIAL_PMACZILOG_CONSOLE
         bool "Console on PowerMac z85c30 serial port"
         depends on SERIAL_PMACZILOG=y