[patch 1/2] 8250: add serial8250_register_port_at() for requesting specific ttyS lines

[Bjorn Helgaas]

Add an interface for registering a new UART with a specific ttyS name.

Signed-off-by: Bjorn Helgaas <bjorn.helgaas@xxxxxx>

Index: work5/include/linux/serial_8250.h
===================================================================
--- work5.orig/include/linux/serial_8250.h	2008-01-15 16:31:49.000000000 -0700
+++ work5/include/linux/serial_8250.h	2008-01-15 16:32:42.000000000 -0700
@@ -56,6 +56,7 @@
 struct uart_port;
 
 int serial8250_register_port(struct uart_port *);
+int serial8250_register_port_at(struct uart_port *, int line);
 void serial8250_unregister_port(int line);
 void serial8250_suspend_port(int line);
 void serial8250_resume_port(int line);
Index: work5/drivers/serial/8250.c
===================================================================
--- work5.orig/drivers/serial/8250.c	2008-01-15 16:31:49.000000000 -0700
+++ work5/drivers/serial/8250.c	2008-01-16 09:32:20.000000000 -0700
@@ -2785,6 +2785,25 @@
 	return NULL;
 }
 
+static int serial8250_add_port(struct uart_8250_port *uart, struct uart_port *port)
+{
+	uart_remove_one_port(&serial8250_reg, &uart->port);
+
+	uart->port.iobase   = port->iobase;
+	uart->port.membase  = port->membase;
+	uart->port.irq      = port->irq;
+	uart->port.uartclk  = port->uartclk;
+	uart->port.fifosize = port->fifosize;
+	uart->port.regshift = port->regshift;
+	uart->port.iotype   = port->iotype;
+	uart->port.flags    = port->flags | UPF_BOOT_AUTOCONF;
+	uart->port.mapbase  = port->mapbase;
+	if (port->dev)
+		uart->port.dev = port->dev;
+
+	return uart_add_one_port(&serial8250_reg, &uart->port);
+}
+
 /**
  *	serial8250_register_port - register a serial port
  *	@port: serial port template
@@ -2809,32 +2828,58 @@
 	mutex_lock(&serial_mutex);
 
 	uart = serial8250_find_match_or_unused(port);
-	if (uart) {
-		uart_remove_one_port(&serial8250_reg, &uart->port);
+	if (uart)
+		ret = serial8250_add_port(uart, port);
 
-		uart->port.iobase   = port->iobase;
-		uart->port.membase  = port->membase;
-		uart->port.irq      = port->irq;
-		uart->port.uartclk  = port->uartclk;
-		uart->port.fifosize = port->fifosize;
-		uart->port.regshift = port->regshift;
-		uart->port.iotype   = port->iotype;
-		uart->port.flags    = port->flags | UPF_BOOT_AUTOCONF;
-		uart->port.mapbase  = port->mapbase;
-		if (port->dev)
-			uart->port.dev = port->dev;
-
-		ret = uart_add_one_port(&serial8250_reg, &uart->port);
-		if (ret == 0)
-			ret = uart->port.line;
-	}
 	mutex_unlock(&serial_mutex);
 
+	if (ret == 0)
+		return uart->port.line;
 	return ret;
 }
 EXPORT_SYMBOL(serial8250_register_port);
 
 /**
+ *	serial8250_register_port_at - register a serial port at a specific line
+ *	@port: serial port template
+ *	@line: desired line
+ *
+ *	Same as serial8250_register_port(), except that we request a
+ *	specific ttyS name.  This is used for well-known ports like
+ *	COM1-COM4, which people expect to always be ttyS0-ttyS3.
+ *
+ *	This fails if the requested line is already in use, even though
+ *	other lines might still be available.  The caller can retry with
+ *	serial8250_register_port() if desired.
+ */
+int serial8250_register_port_at(struct uart_port *port, int line)
+{
+	struct uart_8250_port *uart;
+	int ret;
+
+	if (port->uartclk == 0)
+		return -EINVAL;
+
+	if (line >= nr_uarts)
+		return -ENOSPC;
+
+	mutex_lock(&serial_mutex);
+
+	uart = &serial8250_ports[line];
+	if (uart->port.type == PORT_UNKNOWN && uart->port.iobase == 0)
+		ret = serial8250_add_port(uart, port);
+	else
+		ret = -EBUSY;
+
+	mutex_unlock(&serial_mutex);
+
+	if (ret == 0)
+		return uart->port.line;
+	return ret;
+}
+EXPORT_SYMBOL(serial8250_register_port_at);
+
+/**
  *	serial8250_unregister_port - remove a 16x50 serial port at runtime
  *	@line: serial line number
  *

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