[PATCH v1 02/14] serial: core: Add UPIO_UNSET constant for unset port type

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In some APIs we would like to assign the special value to iotype
and compare against it in another places. Introduce UPIO_UNSET
for this purpose.

Note, we can't use 0, because it's a valid value for IO port access.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
 include/linux/serial_core.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h
index 2d2ec99eca93..2b0526ae1fac 100644
--- a/include/linux/serial_core.h
+++ b/include/linux/serial_core.h
@@ -470,6 +470,7 @@ struct uart_port {
 	unsigned char		iotype;			/* io access style */
+#define UPIO_UNSET		((unsigned char)~0U)	/* UCHAR_MAX */
 #define UPIO_PORT		(SERIAL_IO_PORT)	/* 8b I/O port access */
 #define UPIO_HUB6		(SERIAL_IO_HUB6)	/* Hub6 ISA card */
 #define UPIO_MEM		(SERIAL_IO_MEM)		/* driver-specific */

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