use small array with index to handle irq locking for serial port
hope 32 slot is enough

v2: according to Eric, move irq_no into irq_info, and not clean irq_no

Signed-off-by: Yinghai Lu <yhlu.kernel@gmail.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
---
 drivers/serial/8250.c |   45 +++++++++++++++++++++++++++++++++++++++++----
 1 files changed, 41 insertions(+), 4 deletions(-)

diff --git a/drivers/serial/8250.c b/drivers/serial/8250.c
index 3920324..595b956 100644
--- a/drivers/serial/8250.c
+++ b/drivers/serial/8250.c
@@ -147,9 +147,39 @@ struct uart_8250_port {
 struct irq_info {
 	spinlock_t		lock;
 	struct list_head	*head;
+	int irq_no;
 };
 
-static struct irq_info irq_lists[NR_IRQS];
+#define NR_IRQ_INFO	32
+
+static struct irq_info irq_lists[NR_IRQ_INFO] = {
+	[0 ... NR_IRQ_INFO-1] = {
+		.irq_no = -1,
+	}
+};
+
+static struct irq_info *get_irq_info(int irq, int with_free)
+{
+	int i, first_free = -1;
+
+	for (i = 0; i < NR_IRQ_INFO; i++) {
+		if (irq_lists[i].irq_no == irq)
+			return &irq_lists[i];
+		if (irq_lists[i].irq_no == -1 && first_free == -1)
+			first_free = i;
+	}
+	if (!with_free)
+		return NULL;
+
+	if (first_free != -1) {
+		irq_lists[first_free].irq_no = irq;
+		return &irq_lists[first_free];
+	}
+
+	WARN_ON("NR_IRQ_INFO too small");
+
+	return NULL;
+}
 
 /*
  * Here we define the default xmit fifo size used for each type of UART.
@@ -1554,9 +1584,12 @@ static void serial_do_unlink(struct irq_info *i, struct uart_8250_port *up)
 
 static int serial_link_irq_chain(struct uart_8250_port *up)
 {
-	struct irq_info *i = irq_lists + up->port.irq;
+	struct irq_info *i = get_irq_info(up->port.irq, 1);
 	int ret, irq_flags = up->port.flags & UPF_SHARE_IRQ ? IRQF_SHARED : 0;
 
+	if (!i)
+		return -1;
+
 	spin_lock_irq(&i->lock);
 
 	if (i->head) {
@@ -1580,7 +1613,11 @@ static int serial_link_irq_chain(struct uart_8250_port *up)
 
 static void serial_unlink_irq_chain(struct uart_8250_port *up)
 {
-	struct irq_info *i = irq_lists + up->port.irq;
+	int irq_no = up->port.irq;
+	struct irq_info *i = get_irq_info(irq_no, 0);
+
+	if (!i)
+		return;
 
 	BUG_ON(i->head == NULL);
 
@@ -2964,7 +3001,7 @@ static int __init serial8250_init(void)
 		"%d ports, IRQ sharing %sabled\n", nr_uarts,
 		share_irqs ? "en" : "dis");
 
-	for (i = 0; i < nr_irqs; i++)
+	for (i = 0; i < NR_IRQ_INFO; i++)
 		spin_lock_init(&irq_lists[i].lock);
 
 	ret = uart_register_driver(&serial8250_reg);
-- 
1.5.4.5

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