tty: Cris has a nice RS485 ioctl so we should steal it

JP Tosoni observed:

"About a RS485 ioctl: could you consider the attached files which are
 already in the Linux kernel (in include/asm-cris).  They define a
 TIOCSERSETRS485 (ioctl.h), and the data structure (rs485.h)
 with allows to specify timings. Sounds just like what we want ?"

and he's right: sort of. Rework the structure to use flag bits and make the
time delay a fixed sized field so we don't get 32/64bit problems. Add the ioctls
to x86 so that people know what to add to their platform of choice.

Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 16 insertions, 0 deletions

diff --git a/include/linux/serial.h b/include/linux/serial.h
index deb714314fb1..1ea8d9265bf6 100644
--- a/include/linux/serial.h
+++ b/include/linux/serial.h
@@ -173,6 +173,22 @@ struct serial_icounter_struct {
         int reserved[9];
 };
 
+/*
+ * Serial interface for controlling RS485 settings on chips with suitable
+ * support. Set with TIOCSRS485 and get with TIOCGRS485 if supported by your
+ * platform. The set function returns the new state, with any unsupported bits
+ * reverted appropriately.
+ */
+
+struct serial_rs485 {
+        __u32   flags;                  /* RS485 feature flags */
+#define SER_RS485_ENABLED               (1 << 0)
+#define SER_RS485_RTS_ON_SEND           (1 << 1)
+#define SER_RS485_RTS_AFTER_SEND        (1 << 2)
+        __u32   delay_rts_before_send;  /* Milliseconds */
+        __u32   padding[6];             /* Memory is cheap, new structs
+                                           are a royal PITA .. */
+};
 
 #ifdef __KERNEL__
 #include <linux/compiler.h>