[S390] cio: unit check handling during internal I/O

Send unit checks that occur during internal I/O to the device driver
and react according to its return code.
Signed-off-by: Michael Ernst <mernst@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/include/asm/ccwdev.h

@@ -91,6 +91,14 @@ struct ccw_device {
 	void (*handler) (struct ccw_device *, unsigned long, struct irb *);
 };
 
+/*
+ * Possible CIO actions triggered by the unit check handler.
+ */
+enum uc_todo {
+	UC_TODO_RETRY,
+	UC_TODO_RETRY_ON_NEW_PATH,
+	UC_TODO_STOP
+};
 
 /**
  * struct ccw driver - device driver for channel attached devices
@@ -107,6 +115,7 @@ struct ccw_device {
  * @freeze: callback for freezing during hibernation snapshotting
  * @thaw: undo work done in @freeze
  * @restore: callback for restoring after hibernation
+ * @uc_handler: callback for unit check handler
  * @driver: embedded device driver structure
  * @name: device driver name
  */
@@ -124,6 +133,7 @@ struct ccw_driver {
 	int (*freeze)(struct ccw_device *);
 	int (*thaw) (struct ccw_device *);
 	int (*restore)(struct ccw_device *);
+	enum uc_todo (*uc_handler) (struct ccw_device *, struct irb *);
 	struct device_driver driver;
 	char *name;
 };

drivers/s390/cio/ccwreq.c

@@ -159,6 +159,7 @@ static enum io_status ccwreq_status(struct ccw_device *cdev, struct irb *lcirb)
 {
 	struct irb *irb = &cdev->private->irb;
 	struct cmd_scsw *scsw = &irb->scsw.cmd;
+	enum uc_todo todo;
 
 	/* Perform BASIC SENSE if needed. */
 	if (ccw_device_accumulate_and_sense(cdev, lcirb))
@@ -178,6 +179,20 @@ static enum io_status ccwreq_status(struct ccw_device *cdev, struct irb *lcirb)
 		/* Check for command reject. */
 		if (irb->ecw[0] & SNS0_CMD_REJECT)
 			return IO_REJECTED;
+		/* Ask the driver what to do */
+		if (cdev->drv && cdev->drv->uc_handler) {
+			todo = cdev->drv->uc_handler(cdev, lcirb);
+			switch (todo) {
+			case UC_TODO_RETRY:
+				return IO_STATUS_ERROR;
+			case UC_TODO_RETRY_ON_NEW_PATH:
+				return IO_PATH_ERROR;
+			case UC_TODO_STOP:
+				return IO_REJECTED;
+			default:
+				return IO_STATUS_ERROR;
+			}
+		}
 		/* Assume that unexpected SENSE data implies an error. */
 		return IO_STATUS_ERROR;
 	}