[PATCH] s390: introduce for_each_subchannel

for_each_subchannel() is an iterator calling a function for every possible
subchannel id until non-zero is returned.  Convert the current iterating
functions to it.

Signed-off-by: Cornelia Huck <cohuck@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

5 files changed, 318 insertions, 290 deletions

diff --git a/drivers/s390/cio/blacklist.c b/drivers/s390/cio/blacklist.c
index a4b03031ff50..25e98483d4e4 100644
--- a/drivers/s390/cio/blacklist.c
+++ b/drivers/s390/cio/blacklist.c
@@ -219,6 +219,27 @@ is_blacklisted (int devno)
 }
 
 #ifdef CONFIG_PROC_FS
+static int
+__s390_redo_validation(struct subchannel_id schid, void *data)
+{
+        int ret;
+        struct subchannel *sch;
+
+        sch = get_subchannel_by_schid(schid);
+        if (sch) {
+                /* Already known. */
+                put_device(&sch->dev);
+                return 0;
+        }
+        ret = css_probe_device(schid);
+        if (ret == -ENXIO)
+                return ret; /* We're through. */
+        if (ret == -ENOMEM)
+                /* Stop validation for now. Bad, but no need for a panic. */
+                return ret;
+        return 0;
+}
+
 /*
  * Function: s390_redo_validation
  * Look for no longer blacklisted devices
@@ -226,30 +247,9 @@ is_blacklisted (int devno)
 static inline void
 s390_redo_validation (void)
 {
-        struct subchannel_id schid;
-
         CIO_TRACE_EVENT (0, "redoval");
-        init_subchannel_id(&schid);
-        do {
-                int ret;
-                struct subchannel *sch;
-
-                sch = get_subchannel_by_schid(schid);
-                if (sch) {
-                        /* Already known. */
-                        put_device(&sch->dev);
-                        continue;
-                }
-                ret = css_probe_device(schid);
-                if (ret == -ENXIO)
-                        break; /* We're through. */
-                if (ret == -ENOMEM)
-                        /*
-                         * Stop validation for now. Bad, but no need for a
-                         * panic.
-                         */
-                        break;
-        } while (schid.sch_no++ < __MAX_SUBCHANNEL);
+
+        for_each_subchannel(__s390_redo_validation, NULL);
 }
 
 /*
diff --git a/drivers/s390/cio/chsc.c b/drivers/s390/cio/chsc.c
index aff5d149b729..78e082311f48 100644
--- a/drivers/s390/cio/chsc.c
+++ b/drivers/s390/cio/chsc.c
@@ -310,9 +310,14 @@ s390_set_chpid_offline( __u8 chpid)
                 queue_work(slow_path_wq, &slow_path_work);
 }
 
+struct res_acc_data {
+        struct channel_path *chp;
+        u32 fla_mask;
+        u16 fla;
+};
+
 static int
-s390_process_res_acc_sch(u8 chpid, __u16 fla, u32 fla_mask,
-                         struct subchannel *sch)
+s390_process_res_acc_sch(struct res_acc_data *res_data, struct subchannel *sch)
 {
         int found;
         int chp;
@@ -324,8 +329,9 @@ s390_process_res_acc_sch(u8 chpid, __u16 fla, u32 fla_mask,
                  * check if chpid is in information updated by ssd
                  */
                 if (sch->ssd_info.valid &&
-                    sch->ssd_info.chpid[chp] == chpid &&
-                    (sch->ssd_info.fla[chp] & fla_mask) == fla) {
+                    sch->ssd_info.chpid[chp] == res_data->chp->id &&
+                    (sch->ssd_info.fla[chp] & res_data->fla_mask)
+                    == res_data->fla) {
                         found = 1;
                         break;
                 }
@@ -345,18 +351,80 @@ s390_process_res_acc_sch(u8 chpid, __u16 fla, u32 fla_mask,
         return 0x80 >> chp;
 }
 
+static inline int
+s390_process_res_acc_new_sch(struct subchannel_id schid)
+{
+        struct schib schib;
+        int ret;
+        /*
+         * We don't know the device yet, but since a path
+         * may be available now to the device we'll have
+         * to do recognition again.
+         * Since we don't have any idea about which chpid
+         * that beast may be on we'll have to do a stsch
+         * on all devices, grr...
+         */
+        if (stsch(schid, &schib))
+                /* We're through */
+                return need_rescan ? -EAGAIN : -ENXIO;
+
+        /* Put it on the slow path. */
+        ret = css_enqueue_subchannel_slow(schid);
+        if (ret) {
+                css_clear_subchannel_slow_list();
+                need_rescan = 1;
+                return -EAGAIN;
+        }
+        return 0;
+}
+
 static int
-s390_process_res_acc (u8 chpid, __u16 fla, u32 fla_mask)
+__s390_process_res_acc(struct subchannel_id schid, void *data)
 {
+        int chp_mask, old_lpm;
+        struct res_acc_data *res_data;
         struct subchannel *sch;
+
+        res_data = (struct res_acc_data *)data;
+        sch = get_subchannel_by_schid(schid);
+        if (!sch)
+                /* Check if a subchannel is newly available. */
+                return s390_process_res_acc_new_sch(schid);
+
+        spin_lock_irq(&sch->lock);
+
+        chp_mask = s390_process_res_acc_sch(res_data, sch);
+
+        if (chp_mask == 0) {
+                spin_unlock_irq(&sch->lock);
+                return 0;
+        }
+        old_lpm = sch->lpm;
+        sch->lpm = ((sch->schib.pmcw.pim &
+                     sch->schib.pmcw.pam &
+                     sch->schib.pmcw.pom)
+                    | chp_mask) & sch->opm;
+        if (!old_lpm && sch->lpm)
+                device_trigger_reprobe(sch);
+        else if (sch->driver && sch->driver->verify)
+                sch->driver->verify(&sch->dev);
+
+        spin_unlock_irq(&sch->lock);
+        put_device(&sch->dev);
+        return (res_data->fla_mask == 0xffff) ? -ENODEV : 0;
+}
+
+
+static int
+s390_process_res_acc (struct res_acc_data *res_data)
+{
         int rc;
-        struct subchannel_id schid;
         char dbf_txt[15];
 
-        sprintf(dbf_txt, "accpr%x", chpid);
+        sprintf(dbf_txt, "accpr%x", res_data->chp->id);
         CIO_TRACE_EVENT( 2, dbf_txt);
-        if (fla != 0) {
-                sprintf(dbf_txt, "fla%x", fla);
+        if (res_data->fla != 0) {
+                sprintf(dbf_txt, "fla%x", res_data->fla);
                 CIO_TRACE_EVENT( 2, dbf_txt);
         }
 
@@ -367,71 +435,11 @@ s390_process_res_acc (u8 chpid, __u16 fla, u32 fla_mask)
          * The more information we have (info), the less scanning
          * will we have to do.
          */
-
-        if (!get_chp_status(chpid))
-                return 0; /* no need to do the rest */
-
-        rc = 0;
-        init_subchannel_id(&schid);
-        do {
-                int chp_mask, old_lpm;
-
-                sch = get_subchannel_by_schid(schid);
-                if (!sch) {
-                        struct schib schib;
-                        int ret;
-                        /*
-                         * We don't know the device yet, but since a path
-                         * may be available now to the device we'll have
-                         * to do recognition again.
-                         * Since we don't have any idea about which chpid
-                         * that beast may be on we'll have to do a stsch
-                         * on all devices, grr...
-                         */
-                        if (stsch(schid, &schib)) {
-                                /* We're through */
-                                if (need_rescan)
-                                        rc = -EAGAIN;
-                                break;
-                        }
-                        if (need_rescan) {
-                                rc = -EAGAIN;
-                                continue;
-                        }
-                        /* Put it on the slow path. */
-                        ret = css_enqueue_subchannel_slow(schid);
-                        if (ret) {
-                                css_clear_subchannel_slow_list();
-                                need_rescan = 1;
-                        }
-                        rc = -EAGAIN;
-                        continue;
-                }
-        
-                spin_lock_irq(&sch->lock);
-
-                chp_mask = s390_process_res_acc_sch(chpid, fla, fla_mask, sch);
-
-                if (chp_mask == 0) {
-
-                        spin_unlock_irq(&sch->lock);
-                        continue;
-                }
-                old_lpm = sch->lpm;
-                sch->lpm = ((sch->schib.pmcw.pim &
-                             sch->schib.pmcw.pam &
-                             sch->schib.pmcw.pom)
-                            | chp_mask) & sch->opm;
-                if (!old_lpm && sch->lpm)
-                        device_trigger_reprobe(sch);
-                else if (sch->driver && sch->driver->verify)
-                        sch->driver->verify(&sch->dev);
-
-                spin_unlock_irq(&sch->lock);
-                put_device(&sch->dev);
-                if (fla_mask == 0xffff)
-                        break;
-        } while (schid.sch_no++ < __MAX_SUBCHANNEL);
+        rc = for_each_subchannel(__s390_process_res_acc, res_data);
+        if (css_slow_subchannels_exist())
+                rc = -EAGAIN;
+        else if (rc != -EAGAIN)
+                rc = 0;
         return rc;
 }
 
@@ -469,6 +477,7 @@ int
 chsc_process_crw(void)
 {
         int chpid, ret;
+        struct res_acc_data res_data;
         struct {
                 struct chsc_header request;
                 u32 reserved1;
@@ -503,7 +512,7 @@ chsc_process_crw(void)
         do {
                 int ccode, status;
                 memset(sei_area, 0, sizeof(*sei_area));
-
+                memset(&res_data, 0, sizeof(struct res_acc_data));
                 sei_area->request = (struct chsc_header) {
                         .length = 0x0010,
                         .code   = 0x000e,
@@ -576,26 +585,23 @@ chsc_process_crw(void)
                         if (status < 0)
                                 new_channel_path(sei_area->rsid);
                         else if (!status)
-                                return 0;
-                        if ((sei_area->vf & 0x80) == 0) {
-                                pr_debug("chpid: %x\n", sei_area->rsid);
-                                ret = s390_process_res_acc(sei_area->rsid,
-                                                           0, 0);
-                        } else if ((sei_area->vf & 0xc0) == 0x80) {
-                                pr_debug("chpid: %x link addr: %x\n",
-                                         sei_area->rsid, sei_area->fla);
-                                ret = s390_process_res_acc(sei_area->rsid,
-                                                           sei_area->fla,
-                                                           0xff00);
-                        } else if ((sei_area->vf & 0xc0) == 0xc0) {
-                                pr_debug("chpid: %x full link addr: %x\n",
-                                         sei_area->rsid, sei_area->fla);
-                                ret = s390_process_res_acc(sei_area->rsid,
-                                                           sei_area->fla,
-                                                           0xffff);
+                                break;
+                        res_data.chp = chps[sei_area->rsid];
+                        pr_debug("chpid: %x", sei_area->rsid);
+                        if ((sei_area->vf & 0xc0) != 0) {
+                                res_data.fla = sei_area->fla;
+                                if ((sei_area->vf & 0xc0) == 0xc0) {
+                                        pr_debug(" full link addr: %x",
+                                                 sei_area->fla);
+                                        res_data.fla_mask = 0xffff;
+                                } else {
+                                        pr_debug(" link addr: %x",
+                                                 sei_area->fla);
+                                        res_data.fla_mask = 0xff00;
+                                }
                         }
-                        pr_debug("\n");
-                        
+                        ret = s390_process_res_acc(&res_data);
+                        pr_debug("\n\n");
                         break;
                         
                 default: /* other stuff */
@@ -607,12 +613,70 @@ chsc_process_crw(void)
         return ret;
 }
 
+static inline int
+__chp_add_new_sch(struct subchannel_id schid)
+{
+        struct schib schib;
+        int ret;
+
+        if (stsch(schid, &schib))
+                /* We're through */
+                return need_rescan ? -EAGAIN : -ENXIO;
+
+        /* Put it on the slow path. */
+        ret = css_enqueue_subchannel_slow(schid);
+        if (ret) {
+                css_clear_subchannel_slow_list();
+                need_rescan = 1;
+                return -EAGAIN;
+        }
+        return 0;
+}
+
+
 static int
-chp_add(int chpid)
+__chp_add(struct subchannel_id schid, void *data)
 {
+        int i;
+        struct channel_path *chp;
         struct subchannel *sch;
-        int ret, rc;
-        struct subchannel_id schid;
+
+        chp = (struct channel_path *)data;
+        sch = get_subchannel_by_schid(schid);
+        if (!sch)
+                /* Check if the subchannel is now available. */
+                return __chp_add_new_sch(schid);
+        spin_lock(&sch->lock);
+        for (i=0; i<8; i++)
+                if (sch->schib.pmcw.chpid[i] == chp->id) {
+                        if (stsch(sch->schid, &sch->schib) != 0) {
+                                /* Endgame. */
+                                spin_unlock(&sch->lock);
+                                return -ENXIO;
+                        }
+                        break;
+                }
+        if (i==8) {
+                spin_unlock(&sch->lock);
+                return 0;
+        }
+        sch->lpm = ((sch->schib.pmcw.pim &
+                     sch->schib.pmcw.pam &
+                     sch->schib.pmcw.pom)
+                    | 0x80 >> i) & sch->opm;
+
+        if (sch->driver && sch->driver->verify)
+                sch->driver->verify(&sch->dev);
+
+        spin_unlock(&sch->lock);
+        put_device(&sch->dev);
+        return 0;
+}
+
+static int
+chp_add(int chpid)
+{
+        int rc;
         char dbf_txt[15];
 
         if (!get_chp_status(chpid))
@@ -621,60 +685,11 @@ chp_add(int chpid)
         sprintf(dbf_txt, "cadd%x", chpid);
         CIO_TRACE_EVENT(2, dbf_txt);
 
-        rc = 0;
-        init_subchannel_id(&schid);
-        do {
-                int i;
-
-                sch = get_subchannel_by_schid(schid);
-                if (!sch) {
-                        struct schib schib;
-
-                        if (stsch(schid, &schib)) {
-                                /* We're through */
-                                if (need_rescan)
-                                        rc = -EAGAIN;
-                                break;
-                        }
-                        if (need_rescan) {
-                                rc = -EAGAIN;
-                                continue;
-                        }
-                        /* Put it on the slow path. */
-                        ret = css_enqueue_subchannel_slow(schid);
-                        if (ret) {
-                                css_clear_subchannel_slow_list();
-                                need_rescan = 1;
-                        }
-                        rc = -EAGAIN;
-                        continue;
-                }
-        
-                spin_lock(&sch->lock);
-                for (i=0; i<8; i++)
-                        if (sch->schib.pmcw.chpid[i] == chpid) {
-                                if (stsch(sch->schid, &sch->schib) != 0) {
-                                        /* Endgame. */
-                                        spin_unlock(&sch->lock);
-                                        return rc;
-                                }
-                                break;
-                        }
-                if (i==8) {
-                        spin_unlock(&sch->lock);
-                        return rc;
-                }
-                sch->lpm = ((sch->schib.pmcw.pim &
-                             sch->schib.pmcw.pam &
-                             sch->schib.pmcw.pom)
-                            | 0x80 >> i) & sch->opm;
-
-                if (sch->driver && sch->driver->verify)
-                        sch->driver->verify(&sch->dev);
-
-                spin_unlock(&sch->lock);
-                put_device(&sch->dev);
-        } while (schid.sch_no++ < __MAX_SUBCHANNEL);
+        rc = for_each_subchannel(__chp_add, chps[chpid]);
+        if (css_slow_subchannels_exist())
+                rc = -EAGAIN;
+        if (rc != -EAGAIN)
+                rc = 0;
         return rc;
 }
 
@@ -786,6 +801,29 @@ s390_subchannel_vary_chpid_on(struct device *dev, void *data)
         return 0;
 }
 
+static int
+__s390_vary_chpid_on(struct subchannel_id schid, void *data)
+{
+        struct schib schib;
+        struct subchannel *sch;
+
+        sch = get_subchannel_by_schid(schid);
+        if (sch) {
+                put_device(&sch->dev);
+                return 0;
+        }
+        if (stsch(schid, &schib))
+                /* We're through */
+                return -ENXIO;
+        /* Put it on the slow path. */
+        if (css_enqueue_subchannel_slow(schid)) {
+                css_clear_subchannel_slow_list();
+                need_rescan = 1;
+                return -EAGAIN;
+        }
+        return 0;
+}
+
 /*
  * Function: s390_vary_chpid
  * Varies the specified chpid online or offline
@@ -794,9 +832,7 @@ static int
 s390_vary_chpid( __u8 chpid, int on)
 {
         char dbf_text[15];
-        int status, ret;
-        struct subchannel_id schid;
-        struct subchannel *sch;
+        int status;
 
         sprintf(dbf_text, on?"varyon%x":"varyoff%x", chpid);
         CIO_TRACE_EVENT( 2, dbf_text);
@@ -821,31 +857,9 @@ s390_vary_chpid( __u8 chpid, int on)
         bus_for_each_dev(&css_bus_type, NULL, &chpid, on ?
                          s390_subchannel_vary_chpid_on :
                          s390_subchannel_vary_chpid_off);
-        if (!on)
-                goto out;
-        /* Scan for new devices on varied on path. */
-        init_subchannel_id(&schid);
-        do {
-                struct schib schib;
-
-                if (need_rescan)
-                        break;
-                sch = get_subchannel_by_schid(schid);
-                if (sch) {
-                        put_device(&sch->dev);
-                        continue;
-                }
-                if (stsch(schid, &schib))
-                        /* We're through */
-                        break;
-                /* Put it on the slow path. */
-                ret = css_enqueue_subchannel_slow(schid);
-                if (ret) {
-                        css_clear_subchannel_slow_list();
-                        need_rescan = 1;
-                }
-        } while (schid.sch_no++ < __MAX_SUBCHANNEL);
-out:
+        if (on)
+                /* Scan for new devices on varied on path. */
+                for_each_subchannel(__s390_vary_chpid_on, NULL);
         if (need_rescan || css_slow_subchannels_exist())
                 queue_work(slow_path_wq, &slow_path_work);
         return 0;
diff --git a/drivers/s390/cio/cio.c b/drivers/s390/cio/cio.c
index 396bada65f86..3eb6cb608fc9 100644
--- a/drivers/s390/cio/cio.c
+++ b/drivers/s390/cio/cio.c
@@ -691,7 +691,22 @@ wait_cons_dev (void)
 }
 
 static int
-cio_console_irq(void)
+cio_test_for_console(struct subchannel_id schid, void *data)
+{
+        if (stsch(schid, &console_subchannel.schib) != 0)
+                return -ENXIO;
+        if (console_subchannel.schib.pmcw.dnv &&
+            console_subchannel.schib.pmcw.dev ==
+            console_devno) {
+                console_irq = schid.sch_no;
+                return 1; /* found */
+        }
+        return 0;
+}
+
+
+static int
+cio_get_console_sch_no(void)
 {
         struct subchannel_id schid;
         
@@ -705,16 +720,7 @@ cio_console_irq(void)
                 console_devno = console_subchannel.schib.pmcw.dev;
         } else if (console_devno != -1) {
                 /* At least the console device number is known. */
-                do {
-                        if (stsch(schid, &console_subchannel.schib) != 0)
-                                break;
-                        if (console_subchannel.schib.pmcw.dnv &&
-                            console_subchannel.schib.pmcw.dev ==
-                            console_devno) {
-                                console_irq = schid.sch_no;
-                                break;
-                        }
-                } while (schid.sch_no++ < __MAX_SUBCHANNEL);
+                for_each_subchannel(cio_test_for_console, NULL);
                 if (console_irq == -1)
                         return -1;
         } else {
@@ -730,19 +736,19 @@ cio_console_irq(void)
 struct subchannel *
 cio_probe_console(void)
 {
-        int irq, ret;
+        int sch_no, ret;
         struct subchannel_id schid;
 
         if (xchg(&console_subchannel_in_use, 1) != 0)
                 return ERR_PTR(-EBUSY);
-        irq = cio_console_irq();
-        if (irq == -1) {
+        sch_no = cio_get_console_sch_no();
+        if (sch_no == -1) {
                 console_subchannel_in_use = 0;
                 return ERR_PTR(-ENODEV);
         }
         memset(&console_subchannel, 0, sizeof(struct subchannel));
         init_subchannel_id(&schid);
-        schid.sch_no = irq;
+        schid.sch_no = sch_no;
         ret = cio_validate_subchannel(&console_subchannel, schid);
         if (ret) {
                 console_subchannel_in_use = 0;
@@ -830,32 +836,33 @@ __clear_subchannel_easy(struct subchannel_id schid)
 }
 
 extern void do_reipl(unsigned long devno);
+static int
+__shutdown_subchannel_easy(struct subchannel_id schid, void *data)
+{
+        struct schib schib;
+
+        if (stsch(schid, &schib))
+                return -ENXIO;
+        if (!schib.pmcw.ena)
+                return 0;
+        switch(__disable_subchannel_easy(schid, &schib)) {
+        case 0:
+        case -ENODEV:
+                break;
+        default: /* -EBUSY */
+                if (__clear_subchannel_easy(schid))
+                        break; /* give up... */
+                stsch(schid, &schib);
+                __disable_subchannel_easy(schid, &schib);
+        }
+        return 0;
+}
 
-/* Clear all subchannels. */
 void
 clear_all_subchannels(void)
 {
-        struct subchannel_id schid;
-
         local_irq_disable();
-        init_subchannel_id(&schid);
-        do {
-                struct schib schib;
-                if (stsch(schid, &schib))
-                        break; /* break out of the loop */
-                if (!schib.pmcw.ena)
-                        continue;
-                switch(__disable_subchannel_easy(schid, &schib)) {
-                case 0:
-                case -ENODEV:
-                        break;
-                default: /* -EBUSY */
-                        if (__clear_subchannel_easy(schid))
-                                break; /* give up... jump out of switch */
-                        stsch(schid, &schib);
-                        __disable_subchannel_easy(schid, &schib);
-                }
-        } while (schid.sch_no++ < __MAX_SUBCHANNEL);
+        for_each_subchannel(__shutdown_subchannel_easy, NULL);
 }
 
 /* Make sure all subchannels are quiet before we re-ipl an lpar. */
diff --git a/drivers/s390/cio/css.c b/drivers/s390/cio/css.c
index 5137dafd1e8d..dba632a5f71f 100644
--- a/drivers/s390/cio/css.c
+++ b/drivers/s390/cio/css.c
@@ -21,7 +21,6 @@
 #include "ioasm.h"
 #include "chsc.h"
 
-unsigned int highest_subchannel;
 int need_rescan = 0;
 int css_init_done = 0;
 
@@ -32,6 +31,22 @@ struct device css_bus_device = {
         .bus_id = "css0",
 };
 
+inline int
+for_each_subchannel(int(*fn)(struct subchannel_id, void *), void *data)
+{
+        struct subchannel_id schid;
+        int ret;
+
+        init_subchannel_id(&schid);
+        ret = -ENODEV;
+        do {
+                ret = fn(schid, data);
+                if (ret)
+                        break;
+        } while (schid.sch_no++ < __MAX_SUBCHANNEL);
+        return ret;
+}
+
 static struct subchannel *
 css_alloc_subchannel(struct subchannel_id schid)
 {
@@ -280,25 +295,10 @@ css_evaluate_subchannel(struct subchannel_id schid, int slow)
         return ret;
 }
 
-static void
-css_rescan_devices(void)
+static int
+css_rescan_devices(struct subchannel_id schid, void *data)
 {
-        int ret;
-        struct subchannel_id schid;
-
-        init_subchannel_id(&schid);
-        do {
-                ret = css_evaluate_subchannel(schid, 1);
-                /* No more memory. It doesn't make sense to continue. No
-                 * panic because this can happen in midflight and just
-                 * because we can't use a new device is no reason to crash
-                 * the system. */
-                if (ret == -ENOMEM)
-                        break;
-                /* -ENXIO indicates that there are no more subchannels. */
-                if (ret == -ENXIO)
-                        break;
-        } while (schid.sch_no++ < __MAX_SUBCHANNEL);
+        return css_evaluate_subchannel(schid, 1);
 }
 
 struct slow_subchannel {
@@ -316,7 +316,7 @@ css_trigger_slow_path(void)
 
         if (need_rescan) {
                 need_rescan = 0;
-                css_rescan_devices();
+                for_each_subchannel(css_rescan_devices, NULL);
                 return;
         }
 
@@ -383,6 +383,43 @@ css_process_crw(int irq)
         return ret;
 }
 
+static int __init
+__init_channel_subsystem(struct subchannel_id schid, void *data)
+{
+        struct subchannel *sch;
+        int ret;
+
+        if (cio_is_console(schid))
+                sch = cio_get_console_subchannel();
+        else {
+                sch = css_alloc_subchannel(schid);
+                if (IS_ERR(sch))
+                        ret = PTR_ERR(sch);
+                else
+                        ret = 0;
+                switch (ret) {
+                case 0:
+                        break;
+                case -ENOMEM:
+                        panic("Out of memory in init_channel_subsystem\n");
+                /* -ENXIO: no more subchannels. */
+                case -ENXIO:
+                        return ret;
+                default:
+                        return 0;
+                }
+        }
+        /*
+         * We register ALL valid subchannels in ioinfo, even those
+         * that have been present before init_channel_subsystem.
+         * These subchannels can't have been registered yet (kmalloc
+         * not working) so we do it now. This is true e.g. for the
+         * console subchannel.
+         */
+        css_register_subchannel(sch);
+        return 0;
+}
+
 static void __init
 css_generate_pgid(void)
 {
@@ -410,7 +447,6 @@ static int __init
 init_channel_subsystem (void)
 {
         int ret;
-        struct subchannel_id schid;
 
         if (chsc_determine_css_characteristics() == 0)
                 css_characteristics_avail = 1;
@@ -426,38 +462,8 @@ init_channel_subsystem (void)
 
         ctl_set_bit(6, 28);
 
-        init_subchannel_id(&schid);
-        do {
-                struct subchannel *sch;
-
-                if (cio_is_console(schid))
-                        sch = cio_get_console_subchannel();
-                else {
-                        sch = css_alloc_subchannel(schid);
-                        if (IS_ERR(sch))
-                                ret = PTR_ERR(sch);
-                        else
-                                ret = 0;
-                        if (ret == -ENOMEM)
-                                panic("Out of memory in "
-                                      "init_channel_subsystem\n");
-                        /* -ENXIO: no more subchannels. */
-                        if (ret == -ENXIO)
-                                break;
-                        if (ret)
-                                continue;
-                }
-                /*
-                 * We register ALL valid subchannels in ioinfo, even those
-                 * that have been present before init_channel_subsystem.
-                 * These subchannels can't have been registered yet (kmalloc
-                 * not working) so we do it now. This is true e.g. for the
-                 * console subchannel.
-                 */
-                css_register_subchannel(sch);
-        } while (schid.sch_no++ < __MAX_SUBCHANNEL);
+        for_each_subchannel(__init_channel_subsystem, NULL);
         return 0;
-
 out_bus:
         bus_unregister(&css_bus_type);
 out:
diff --git a/drivers/s390/cio/css.h b/drivers/s390/cio/css.h
index f26e16daecb5..71efca25476d 100644
--- a/drivers/s390/cio/css.h
+++ b/drivers/s390/cio/css.h
@@ -126,6 +126,7 @@ extern struct css_driver io_subchannel_driver;
 extern int css_probe_device(struct subchannel_id);
 extern struct subchannel * get_subchannel_by_schid(struct subchannel_id);
 extern int css_init_done;
+extern int for_each_subchannel(int(*fn)(struct subchannel_id, void *), void *);
 
 #define __MAX_SUBCHANNEL 65535