console: prepare for non-COMn port support

Widen SERHND_IDX (and use it where needed), introduce a flush low level
driver method, and remove unnecessary peeking of the common code at the
(driver specific) serial port identification string in the "console="
command line option value.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

--- a/xen/arch/x86/smpboot.c
+++ b/xen/arch/x86/smpboot.c
@@ -1017,7 +1017,7 @@ void __init smp_intr_init(void)
      * Also ensure serial interrupts are high priority. We do not
      * want them to be blocked by unacknowledged guest-bound interrupts.
      */
-    for ( seridx = 0; seridx < 2; seridx++ )
+    for ( seridx = 0; seridx <= SERHND_IDX; seridx++ )
     {
         if ( (irq = serial_irq(seridx)) < 0 )
             continue;
--- a/xen/drivers/char/console.c
+++ b/xen/drivers/char/console.c
@@ -539,6 +539,7 @@ void printk(const char *fmt, ...)
 void __init console_init_preirq(void)
 {
     char *p;
+    int sh;
 
     serial_init_preirq();
 
@@ -551,8 +552,9 @@ void __init console_init_preirq(void)
             vga_init();
         else if ( !strncmp(p, "none", 4) )
             continue;
-        else if ( strncmp(p, "com", 3) ||
-                  (sercon_handle = serial_parse_handle(p)) == -1 )
+        else if ( (sh = serial_parse_handle(p)) >= 0 )
+            sercon_handle = sh;
+        else
         {
             char *q = strchr(p, ',');
             if ( q != NULL )
--- a/xen/drivers/char/serial.c
+++ b/xen/drivers/char/serial.c
@@ -22,9 +22,11 @@ size_param("serial_tx_buffer", serial_tx
 #define mask_serial_rxbuf_idx(_i) ((_i)&(serial_rxbufsz-1))
 #define mask_serial_txbuf_idx(_i) ((_i)&(serial_txbufsz-1))
 
-static struct serial_port com[2] = {
-    { .rx_lock = SPIN_LOCK_UNLOCKED, .tx_lock = SPIN_LOCK_UNLOCKED }, 
-    { .rx_lock = SPIN_LOCK_UNLOCKED, .tx_lock = SPIN_LOCK_UNLOCKED }
+static struct serial_port com[SERHND_IDX + 1] = {
+    [0 ... SERHND_IDX] = {
+        .rx_lock = SPIN_LOCK_UNLOCKED,
+        .tx_lock = SPIN_LOCK_UNLOCKED
+    }
 };
 
 void serial_rx_interrupt(struct serial_port *port, struct cpu_user_regs *regs)
@@ -81,6 +83,8 @@ void serial_tx_interrupt(struct serial_p
             port->driver->putc(
                 port, port->txbuf[mask_serial_txbuf_idx(port->txbufc++)]);
         }
+        if ( i && port->driver->flush )
+            port->driver->flush(port);
     }
 
     spin_unlock(&port->tx_lock);
@@ -175,6 +179,9 @@ void serial_putc(int handle, char c)
 
     __serial_putc(port, c);
 
+    if ( port->driver->flush )
+        port->driver->flush(port);
+
     spin_unlock_irqrestore(&port->tx_lock, flags);
 }
 
@@ -206,6 +213,9 @@ void serial_puts(int handle, const char 
         __serial_putc(port, c);
     }
 
+    if ( port->driver->flush )
+        port->driver->flush(port);
+
     spin_unlock_irqrestore(&port->tx_lock, flags);
 }
 
@@ -261,10 +271,10 @@ int __init serial_parse_handle(char *con
     switch ( conf[3] )
     {
     case '1':
-        handle = 0;
+        handle = SERHND_COM1;
         break;
     case '2':
-        handle = 1;
+        handle = SERHND_COM2;
         break;
     default:
         goto fail;
@@ -365,6 +375,8 @@ void serial_start_sync(int handle)
             port->driver->putc(
                 port, port->txbuf[mask_serial_txbuf_idx(port->txbufc++)]);
         }
+        if ( port->driver->flush )
+            port->driver->flush(port);
     }
 
     spin_unlock_irqrestore(&port->tx_lock, flags);
--- a/xen/include/xen/serial.h
+++ b/xen/include/xen/serial.h
@@ -60,6 +60,8 @@ struct uart_driver {
     int  (*tx_empty)(struct serial_port *);
     /* Put a character onto the serial line. */
     void (*putc)(struct serial_port *, char);
+    /* Flush accumulated characters. */
+    void (*flush)(struct serial_port *);
     /* Get a character from the serial line: returns 0 if none available. */
     int  (*getc)(struct serial_port *, char *);
     /* Get IRQ number for this port's serial line: returns -1 if none. */
@@ -67,10 +69,12 @@ struct uart_driver {
 };
 
 /* 'Serial handles' are composed from the following fields. */
-#define SERHND_IDX      (1<<0) /* COM1 or COM2?                           */
-#define SERHND_HI       (1<<1) /* Mux/demux each transferred char by MSB. */
-#define SERHND_LO       (1<<2) /* Ditto, except that the MSB is cleared.  */
-#define SERHND_COOKED   (1<<3) /* Newline/carriage-return translation?    */
+#define SERHND_IDX      (3<<0) /* COM1 or COM2?                           */
+# define SERHND_COM1    (0<<0)
+# define SERHND_COM2    (1<<0)
+#define SERHND_HI       (1<<2) /* Mux/demux each transferred char by MSB. */
+#define SERHND_LO       (1<<3) /* Ditto, except that the MSB is cleared.  */
+#define SERHND_COOKED   (1<<4) /* Newline/carriage-return translation?    */
 
 /* Two-stage initialisation (before/after IRQ-subsystem initialisation). */
 void serial_init_preirq(void);