On Wed, 16 Sep 2009 19:38:36 -0700
Greg KH [off-list ref] wrote:

/**
+ * ks_irq - device interrupt handler
+ * @irq: Interrupt number passed from the IRQ hnalder.
+ * @pw: The private word passed to register_irq(), our struct ks_net.
+ *
+ * This is the handler invoked to find out what happened
+ *
+ * Read the interrupt status, work out what needs to be done and then clear
+ * any of the interrupts that are not needed.
+ */
+
+static irqreturn_t ks_irq(int irq, void *pw)
+{
+	struct ks_net *ks = pw;
+	struct net_device *netdev = ks->netdev;
+	u16 status;
+
+	/*this should be the first in IRQ handler */
+	ks_save_cmd_reg(ks);
+
+	status = ks_rdreg16(ks, KS_ISR);
+	ks_wrreg16(ks, KS_ISR, status);

if status == 0 or status == ~0 then device should not return IRQ_HANDLED.
In the former case, the IRQ is shared, in later case the device is not present
on the bus (hotplug).