IB/ipath: Support blinking LEDs with an led_override file

When we want to find an InfiniPath HCA in a rack of nodes, it is often
expeditious to blink the status LEDs via a userspace /sys file.

A write-only led_override "file" is published per device. Writes to
this file are interpreted as (string form) numbers, and the resulting
value sent to ipath_set_led_override(). The upper eight bits are
interpretted as a 4.4 fixed-point "frequency in Hertz", and the bottom
two 4-bit values are alternately (D0..3, then D4..7) used by the
board-specific LED-setting function to override the normal state.

Signed-off-by: Michael Albaugh <michael.albaugh@qlogic.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>

drivers/infiniband/hw/ipath/ipath_kernel.h

@@ -575,6 +575,16 @@ struct ipath_devdata {
 	u16 ipath_gpio_scl_num;
 	u64 ipath_gpio_sda;
 	u64 ipath_gpio_scl;
+
+	/* used to override LED behavior */
+	u8 ipath_led_override;  /* Substituted for normal value, if non-zero */
+	u16 ipath_led_override_timeoff; /* delta to next timer event */
+	u8 ipath_led_override_vals[2]; /* Alternates per blink-frame */
+	u8 ipath_led_override_phase; /* Just counts, LSB picks from vals[] */
+	atomic_t ipath_led_override_timer_active;
+	/* Used to flash LEDs in override mode */
+	struct timer_list ipath_led_override_timer;
+
 };
 
 /* Private data for file operations */
@@ -716,6 +726,15 @@ void ipath_get_eeprom_info(struct ipath_devdata *);
 u64 ipath_snap_cntr(struct ipath_devdata *, ipath_creg);
 void ipath_disarm_senderrbufs(struct ipath_devdata *, int);
 
+/*
+ * Set LED override, only the two LSBs have "public" meaning, but
+ * any non-zero value substitutes them for the Link and LinkTrain
+ * LED states.
+ */
+#define IPATH_LED_PHYS 1 /* Physical (linktraining) GREEN LED */
+#define IPATH_LED_LOG 2  /* Logical (link) YELLOW LED */
+void ipath_set_led_override(struct ipath_devdata *dd, unsigned int val);
+
 /*
  * number of words used for protocol header if not set by ipath_userinit();
  */