s390/cio: clarify cssid usage

Currently the cssid in various structures is used as the id of
the respective channel subsystem. Sometimes however we call the
index in the channel_subsystems array cssid. In some places the
id is even used as the index.

Provide a new define MAX_CSS_IDX and use it where appropriate.
In addition to that provide a dummy function to find a channel
subsystem by its id and a macro to iterate over the channel
subsystems.
Signed-off-by: Sebastian Ott <sebott@linux.vnet.ibm.com>
Reviewed-by: Peter Oberparleiter <oberpar@linux.vnet.ibm.com>
Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

drivers/s390/cio/chp.c

@@ -444,6 +444,7 @@ int chp_update_desc(struct channel_path *chp)
  */
 int chp_new(struct chp_id chpid)
 {
+	struct channel_subsystem *css = css_by_id(chpid.cssid);
 	struct channel_path *chp;
 	int ret;
 
@@ -456,7 +457,7 @@ int chp_new(struct chp_id chpid)
 	/* fill in status, etc. */
 	chp->chpid = chpid;
 	chp->state = 1;
-	chp->dev.parent = &channel_subsystems[chpid.cssid]->device;
+	chp->dev.parent = &css->device;
 	chp->dev.groups = chp_attr_groups;
 	chp->dev.release = chp_release;
 	mutex_init(&chp->lock);
@@ -479,17 +480,17 @@ int chp_new(struct chp_id chpid)
 		put_device(&chp->dev);
 		goto out;
 	}
-	mutex_lock(&channel_subsystems[chpid.cssid]->mutex);
-	if (channel_subsystems[chpid.cssid]->cm_enabled) {
+	mutex_lock(&css->mutex);
+	if (css->cm_enabled) {
 		ret = chp_add_cmg_attr(chp);
 		if (ret) {
 			device_unregister(&chp->dev);
-			mutex_unlock(&channel_subsystems[chpid.cssid]->mutex);
+			mutex_unlock(&css->mutex);
 			goto out;
 		}
 	}
-	channel_subsystems[chpid.cssid]->chps[chpid.id] = chp;
-	mutex_unlock(&channel_subsystems[chpid.cssid]->mutex);
+	css->chps[chpid.id] = chp;
+	mutex_unlock(&css->mutex);
 	goto out;
 out_free:
 	kfree(chp);

drivers/s390/cio/chp.h

@@ -54,7 +54,7 @@ struct channel_path {
 /* Return channel_path struct for given chpid. */
 static inline struct channel_path *chpid_to_chp(struct chp_id chpid)
 {
-	return channel_subsystems[chpid.cssid]->chps[chpid.id];
+	return css_by_id(chpid.cssid)->chps[chpid.id];
 }
 
 int chp_get_status(struct chp_id chpid);

drivers/s390/cio/css.c

@@ -36,7 +36,8 @@
 int css_init_done = 0;
 int max_ssid;
 
-struct channel_subsystem *channel_subsystems[__MAX_CSSID + 1];
+#define MAX_CSS_IDX 0
+struct channel_subsystem *channel_subsystems[MAX_CSS_IDX + 1];
 static struct bus_type css_bus_type;
 
 int
@@ -805,13 +806,11 @@ static int css_reboot_event(struct notifier_block *this,
 			    unsigned long event,
 			    void *ptr)
 {
-	int ret, i;
-
-	ret = NOTIFY_DONE;
-	for (i = 0; i <= __MAX_CSSID; i++) {
 	struct channel_subsystem *css;
+	int ret;
 
-		css = channel_subsystems[i];
+	ret = NOTIFY_DONE;
+	for_each_css(css) {
 		mutex_lock(&css->mutex);
 		if (css->cm_enabled)
 			if (chsc_secm(css, 0))
@@ -835,16 +834,14 @@ static struct notifier_block css_reboot_notifier = {
 static int css_power_event(struct notifier_block *this, unsigned long event,
 			   void *ptr)
 {
-	int ret, i;
+	struct channel_subsystem *css;
+	int ret;
 
 	switch (event) {
 	case PM_HIBERNATION_PREPARE:
 	case PM_SUSPEND_PREPARE:
 		ret = NOTIFY_DONE;
-		for (i = 0; i <= __MAX_CSSID; i++) {
-			struct channel_subsystem *css;
-
-			css = channel_subsystems[i];
+		for_each_css(css) {
 			mutex_lock(&css->mutex);
 			if (!css->cm_enabled) {
 				mutex_unlock(&css->mutex);
@@ -858,10 +855,7 @@ static int css_power_event(struct notifier_block *this, unsigned long event,
 	case PM_POST_HIBERNATION:
 	case PM_POST_SUSPEND:
 		ret = NOTIFY_DONE;
-		for (i = 0; i <= __MAX_CSSID; i++) {
-			struct channel_subsystem *css;
-
-			css = channel_subsystems[i];
+		for_each_css(css) {
 			mutex_lock(&css->mutex);
 			if (!css->cm_enabled) {
 				mutex_unlock(&css->mutex);
@@ -916,7 +910,7 @@ static int __init css_bus_init(void)
 		goto out;
 
 	/* Setup css structure. */
-	for (i = 0; i <= __MAX_CSSID; i++) {
+	for (i = 0; i <= MAX_CSS_IDX; i++) {
 		struct channel_subsystem *css;
 
 		css = kmalloc(sizeof(struct channel_subsystem), GFP_KERNEL);
@@ -993,10 +987,8 @@ static int __init css_bus_init(void)
 static void __init css_bus_cleanup(void)
 {
 	struct channel_subsystem *css;
-	int i;
 
-	for (i = 0; i <= __MAX_CSSID; i++) {
-		css = channel_subsystems[i];
+	for_each_css(css) {
 		device_unregister(&css->pseudo_subchannel->dev);
 		css->pseudo_subchannel = NULL;
 		if (css_chsc_characteristics.secm)

drivers/s390/cio/css.h

@@ -130,6 +130,16 @@ struct channel_subsystem {
 
 extern struct channel_subsystem *channel_subsystems[];
 
+/* Dummy helper which needs to change once we support more than one css. */
+static inline struct channel_subsystem *css_by_id(u8 cssid)
+{
+	return channel_subsystems[0];
+}
+
+/* Dummy iterator which needs to change once we support more than one css. */
+#define for_each_css(css)						\
+	for ((css) = channel_subsystems[0]; (css); (css) = NULL)
+
 /* Helper functions to build lists for the slow path. */
 void css_schedule_eval(struct subchannel_id schid);
 void css_schedule_eval_all(void);