[S390] cio: obtain mdc value per channel path

Add support to accumulate the number of 64K-bytes blocks all paths
to a device at least support for a transport command.
Signed-off-by: Sebastian Ott <sebott@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/include/asm/ccwdev.h

@@ -204,6 +204,8 @@ int ccw_device_tm_start_timeout(struct ccw_device *, struct tcw *,
 			    unsigned long, u8, int);
 int ccw_device_tm_intrg(struct ccw_device *cdev);
 
+int ccw_device_get_mdc(struct ccw_device *cdev, u8 mask);
+
 extern int ccw_device_set_online(struct ccw_device *cdev);
 extern int ccw_device_set_offline(struct ccw_device *cdev);
 

drivers/s390/cio/chsc.c

@@ -695,6 +695,25 @@ int chsc_determine_base_channel_path_desc(struct chp_id chpid,
 	return ret;
 }
 
+int chsc_determine_fmt1_channel_path_desc(struct chp_id chpid,
+					  struct channel_path_desc_fmt1 *desc)
+{
+	struct chsc_response_struct *chsc_resp;
+	struct chsc_scpd *scpd_area;
+	int ret;
+
+	spin_lock_irq(&chsc_page_lock);
+	scpd_area = chsc_page;
+	ret = chsc_determine_channel_path_desc(chpid, 0, 0, 1, 0, scpd_area);
+	if (ret)
+		goto out;
+	chsc_resp = (void *)&scpd_area->response;
+	memcpy(desc, &chsc_resp->data, sizeof(*desc));
+out:
+	spin_unlock_irq(&chsc_page_lock);
+	return ret;
+}
+
 static void
 chsc_initialize_cmg_chars(struct channel_path *chp, u8 cmcv,
 			  struct cmg_chars *chars)

drivers/s390/cio/chsc.h

@@ -35,6 +35,22 @@ struct channel_path_desc {
 	u8 chpp;
 } __attribute__ ((packed));
 
+struct channel_path_desc_fmt1 {
+	u8 flags;
+	u8 lsn;
+	u8 desc;
+	u8 chpid;
+	u32:24;
+	u8 chpp;
+	u32 unused[3];
+	u16 mdc;
+	u16:13;
+	u8 r:1;
+	u8 s:1;
+	u8 f:1;
+	u32 zeros[2];
+} __attribute__ ((packed));
+
 struct channel_path;
 
 struct css_chsc_char {
@@ -92,6 +108,8 @@ int chsc_determine_channel_path_desc(struct chp_id chpid, int fmt, int rfmt,
 				     int c, int m, void *page);
 int chsc_determine_base_channel_path_desc(struct chp_id chpid,
 					  struct channel_path_desc *desc);
+int chsc_determine_fmt1_channel_path_desc(struct chp_id chpid,
+					  struct channel_path_desc_fmt1 *desc);
 void chsc_chp_online(struct chp_id chpid);
 void chsc_chp_offline(struct chp_id chpid);
 int chsc_get_channel_measurement_chars(struct channel_path *chp);

drivers/s390/cio/device_ops.c

@@ -686,6 +686,46 @@ int ccw_device_tm_start_timeout(struct ccw_device *cdev, struct tcw *tcw,
 }
 EXPORT_SYMBOL(ccw_device_tm_start_timeout);
 
+/**
+ * ccw_device_get_mdc - accumulate max data count
+ * @cdev: ccw device for which the max data count is accumulated
+ * @mask: mask of paths to use
+ *
+ * Return the number of 64K-bytes blocks all paths at least support
+ * for a transport command. Return values <= 0 indicate failures.
+ */
+int ccw_device_get_mdc(struct ccw_device *cdev, u8 mask)
+{
+	struct subchannel *sch = to_subchannel(cdev->dev.parent);
+	struct channel_path_desc_fmt1 desc;
+	struct chp_id chpid;
+	int mdc = 0, ret, i;
+
+	/* Adjust requested path mask to excluded varied off paths. */
+	if (mask)
+		mask &= sch->lpm;
+	else
+		mask = sch->lpm;
+
+	chp_id_init(&chpid);
+	for (i = 0; i < 8; i++) {
+		if (!(mask & (0x80 >> i)))
+			continue;
+		chpid.id = sch->schib.pmcw.chpid[i];
+		ret = chsc_determine_fmt1_channel_path_desc(chpid, &desc);
+		if (ret)
+			return ret;
+		if (!desc.f)
+			return 0;
+		if (!desc.r)
+			mdc = 1;
+		mdc = mdc ? min(mdc, (int)desc.mdc) : desc.mdc;
+	}
+
+	return mdc;
+}
+EXPORT_SYMBOL(ccw_device_get_mdc);
+
 /**
  * ccw_device_tm_intrg - perform interrogate function
  * @cdev: ccw device on which to perform the interrogate function