[RFC PATCH v2 07/21] serial: 8250_pnp: Add support for deferred probe

[Sunil V L <sunilvl@xxxxxxxxxxxxxxxx>]

With pnp_irq() able to return error code, enhance the serial pnp driver
to support deferred probing. Return -EPROBE_DEFER when pnp_irq() returns
the same so that the driver probe is deferred.

Signed-off-by: Sunil V L <sunilvl@xxxxxxxxxxxxxxxx>
---
 drivers/tty/serial/8250/8250_pnp.c | 18 ++++++++++++++++--
 1 file changed, 16 insertions(+), 2 deletions(-)

diff --git a/drivers/tty/serial/8250/8250_pnp.c b/drivers/tty/serial/8250/8250_pnp.c
index 1974bbadc975..dcb3daf7c816 100644
--- a/drivers/tty/serial/8250/8250_pnp.c
+++ b/drivers/tty/serial/8250/8250_pnp.c
@@ -8,6 +8,7 @@
  *
  *  Ported to the Linux PnP Layer - (C) Adam Belay.
  */
+#include <linux/acpi.h>
 #include <linux/module.h>
 #include <linux/pci.h>
 #include <linux/pnp.h>
@@ -443,8 +444,21 @@ serial_pnp_probe(struct pnp_dev *dev, const struct pnp_device_id *dev_id)
 	}
 
 	memset(&uart, 0, sizeof(uart));
-	if (pnp_irq_valid(dev, 0))
-		uart.port.irq = pnp_irq(dev, 0);
+	if (pnp_irq_valid(dev, 0)) {
+		ret = pnp_irq(dev, 0);
+		if (ret == -EPROBE_DEFER) {
+			struct resource r;
+
+			ret = acpi_irq_get(ACPI_HANDLE(&dev->dev), 0, &r);
+			if (!ret)
+				uart.port.irq = r.start;
+			else
+				return ret;
+		} else {
+			uart.port.irq = ret;
+		}
+	}
+
 	if ((flags & CIR_PORT) && pnp_port_valid(dev, 2)) {
 		uart.port.iobase = pnp_port_start(dev, 2);
 		uart.port.iotype = UPIO_PORT;
-- 
2.39.2