s390/cio: introduce pathmask_to_pos

We often need to correlate an 8 bit path mask with the position
in a channel path array. Introduce and use pathmask_to_pos for
that task.
Reviewed-by: Peter Oberparleiter <oberpar@linux.vnet.ibm.com>
Signed-off-by: Sebastian Ott <sebott@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/include/asm/cio.h

@@ -5,6 +5,7 @@
 #define _ASM_S390_CIO_H_
 
 #include <linux/spinlock.h>
+#include <linux/bitops.h>
 #include <asm/types.h>
 
 #define LPM_ANYPATH 0xff
@@ -296,6 +297,15 @@ static inline int ccw_dev_id_is_equal(struct ccw_dev_id *dev_id1,
 	return 0;
 }
 
+/**
+ * pathmask_to_pos() - find the position of the left-most bit in a pathmask
+ * @mask: pathmask with at least one bit set
+ */
+static inline u8 pathmask_to_pos(u8 mask)
+{
+	return 8 - ffs(mask);
+}
+
 void channel_subsystem_reinit(void);
 extern void css_schedule_reprobe(void);
 

drivers/s390/block/dasd_eckd.c

@@ -1068,8 +1068,7 @@ static int dasd_eckd_read_conf(struct dasd_device *device)
 			path_data->opm |= lpm;
 			continue;	/* no error */
 		}
-		/* translate path mask to position in mask */
-		pos = 8 - ffs(lpm);
+		pos = pathmask_to_pos(lpm);
 		kfree(private->path_conf_data[pos]);
 		if ((__u8 *)private->path_conf_data[pos] ==
 		    private->conf_data) {
@@ -4671,7 +4670,7 @@ static struct dasd_conf_data *dasd_eckd_get_ref_conf(struct dasd_device *device,
 			return conf_data;
 	}
 out:
-	return private->path_conf_data[8 - ffs(lpum)];
+	return private->path_conf_data[pathmask_to_pos(lpum)];
 }
 
 /*
@@ -4716,7 +4715,7 @@ static int dasd_eckd_cuir_scope(struct dasd_device *device, __u8 lpum,
 	for (path = 0x80; path; path >>= 1) {
 		/* initialise data per path */
 		bitmask = mask;
-		pos = 8 - ffs(path);
+		pos = pathmask_to_pos(path);
 		conf_data = private->path_conf_data[pos];
 		pos = 8 - ffs(cuir->ned_map);
 		ned = (char *) &conf_data->neds[pos];
@@ -4937,9 +4936,7 @@ static void dasd_eckd_handle_cuir(struct dasd_device *device, void *messages,
 		      ((u64 *)cuir)[0], ((u64 *)cuir)[1], ((u64 *)cuir)[2],
 		      ((u32 *)cuir)[3]);
 	ccw_device_get_schid(device->cdev, &sch_id);
-	/* get position of path in mask */
-	pos = 8 - ffs(lpum);
-	/* get channel path descriptor from this position */
+	pos = pathmask_to_pos(lpum);
 	desc = ccw_device_get_chp_desc(device->cdev, pos);
 
 	if (cuir->code == CUIR_QUIESCE) {

drivers/s390/cio/device_pgid.c

@@ -133,7 +133,7 @@ static void spid_build_cp(struct ccw_device *cdev, u8 fn)
 {
 	struct ccw_request *req = &cdev->private->req;
 	struct ccw1 *cp = cdev->private->iccws;
-	int i = 8 - ffs(req->lpm);
+	int i = pathmask_to_pos(req->lpm);
 	struct pgid *pgid = &cdev->private->pgid[i];
 
 	pgid->inf.fc	= fn;
@@ -434,7 +434,7 @@ static void snid_build_cp(struct ccw_device *cdev)
 {
 	struct ccw_request *req = &cdev->private->req;
 	struct ccw1 *cp = cdev->private->iccws;
-	int i = 8 - ffs(req->lpm);
+	int i = pathmask_to_pos(req->lpm);
 
 	/* Channel program setup. */
 	cp->cmd_code	= CCW_CMD_SENSE_PGID;