[PATCH 5/9] serial: core: add new I/O type for SPI and I2C bus devices

[Hugo Villeneuve <hugo@hugovil.com>]

From: Hugo Villeneuve <hvilleneuve@dimonoff.com>

I2C/SPI serial drivers don't use the following struct uart_port variables:
    port->membase
    port->mapbase
    port->iobase

However, they are forced to set membase to a non-zero value so that
uart_configure_port() will succeed because of the following check:

    /* If there isn't a port here, don't do anything further. */
    if (!port->iobase && !port->mapbase && !port->membase)
        return;

Add a new I/O type for SPI and I2C bus devices to remove the need to
implement the kind of above-mentioned ambiguous workarounds to make them
work.

Signed-off-by: Hugo Villeneuve <hvilleneuve@dimonoff.com>
---
With this change, uart_match_port() will always return true for UPIO_BUS
types, and this function is not used by any of the SPI/I2C drivers.
---
 drivers/tty/serial/serial_core.c | 11 ++++++-----
 include/linux/serial_core.h      |  1 +
 include/uapi/linux/serial.h      |  1 +
 3 files changed, 8 insertions(+), 5 deletions(-)

diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
index cb5da344305e397b42f47bdbc2c053fc487ed784..0bfdb69817e4259681fbc4658c9a68200aa2b65f 100644
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -2527,11 +2527,10 @@ uart_configure_port(struct uart_driver *drv, struct uart_state *state,
 {
 	unsigned int flags;
 
-	/*
-	 * If there isn't a port here, don't do anything further.
-	 */
-	if (!port->iobase && !port->mapbase && !port->membase)
-		return;
+	/* If there isn't a port here, don't do anything further. */
+	if (uart_iotype_mmio(port->iotype) || uart_iotype_legacy_io(port->iotype))
+		if (!port->iobase && !port->mapbase && !port->membase)
+			return;
 
 	/*
 	 * Now do the auto configuration stuff.  Note that config_port
@@ -3230,6 +3229,8 @@ bool uart_match_port(const struct uart_port *port1,
 			return false;
 		else
 			return true;
+	else if (port1->iotype == UPIO_BUS)
+		return true;
 	else
 		return false;
 }
diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h
index fc3f5ebe389658c197ffc105ce4ac11cacef59bb..626dd939c53c9f920d71aadd360ec0ea0bacce0d 100644
--- a/include/linux/serial_core.h
+++ b/include/linux/serial_core.h
@@ -437,6 +437,7 @@ enum uart_iotype {
 	UPIO_TSI	= SERIAL_IO_TSI,	/* Tsi108/109 type IO */
 	UPIO_MEM32BE	= SERIAL_IO_MEM32BE,	/* 32b big endian */
 	UPIO_MEM16	= SERIAL_IO_MEM16,	/* 16b little endian */
+	UPIO_BUS	= SERIAL_IO_BUS,	/* Serial bus I/O access (ex: SPI, I2C) */
 };
 
 struct uart_port {
diff --git a/include/uapi/linux/serial.h b/include/uapi/linux/serial.h
index de9b4733607e6b61b08ff7089ff90070168ff4a2..e6f61538fc2837a264d27942afaaf3f12e743445 100644
--- a/include/uapi/linux/serial.h
+++ b/include/uapi/linux/serial.h
@@ -72,6 +72,7 @@ struct serial_struct {
 #define SERIAL_IO_TSI	  5
 #define SERIAL_IO_MEM32BE 6
 #define SERIAL_IO_MEM16	7
+#define SERIAL_IO_BUS	8
 
 #define UART_CLEAR_FIFO		0x01
 #define UART_USE_FIFO		0x02

-- 
2.47.3