dm: blk: Allow blk_create_device() to allocate the device number

Allow a devnum parameter of -1 to indicate that the device number should be
alocated automatically. The next highest available device number for that
interface type is used.

Signed-off-by: Simon Glass <sjg@chromium.org>

drivers/block/blk-uclass.c

@@ -411,6 +411,26 @@ int blk_prepare_device(struct udevice *dev)
 	return 0;
 }
 
+int blk_find_max_devnum(enum if_type if_type)
+{
+	struct udevice *dev;
+	int max_devnum = -ENODEV;
+	struct uclass *uc;
+	int ret;
+
+	ret = uclass_get(UCLASS_BLK, &uc);
+	if (ret)
+		return ret;
+	uclass_foreach_dev(dev, uc) {
+		struct blk_desc *desc = dev_get_uclass_platdata(dev);
+
+		if (desc->if_type == if_type && desc->devnum > max_devnum)
+			max_devnum = desc->devnum;
+	}
+
+	return max_devnum;
+}
+
 int blk_create_device(struct udevice *parent, const char *drv_name,
 		      const char *name, int if_type, int devnum, int blksz,
 		      lbaint_t size, struct udevice **devp)
@@ -428,6 +448,15 @@ int blk_create_device(struct udevice *parent, const char *drv_name,
 	desc->lba = size / blksz;
 	desc->part_type = PART_TYPE_UNKNOWN;
 	desc->bdev = dev;
+	if (devnum == -1) {
+		ret = blk_find_max_devnum(if_type);
+		if (ret == -ENODEV)
+			devnum = 0;
+		else if (ret < 0)
+			return ret;
+		else
+			devnum = ret + 1;
+	}
 	desc->devnum = devnum;
 	*devp = dev;
 

include/blk.h

@@ -270,7 +270,8 @@ int blk_next_device(struct udevice **devp);
  * @drv_name:	Driver name to use for the block device
  * @name:	Name for the device
  * @if_type:	Interface type (enum if_type_t)
- * @devnum:	Device number, specific to the interface type
+ * @devnum:	Device number, specific to the interface type, or -1 to
+ *		allocate the next available number
  * @blksz:	Block size of the device in bytes (typically 512)
  * @size:	Total size of the device in bytes
  * @devp:	the new device (which has not been probed)
@@ -299,6 +300,18 @@ int blk_prepare_device(struct udevice *dev);
  */
 int blk_unbind_all(int if_type);
 
+/**
+ * blk_find_max_devnum() - find the maximum device number for an interface type
+ *
+ * Finds the last allocated device number for an interface type @if_type. The
+ * next number is safe to use for a newly allocated device.
+ *
+ * @if_type:	Interface type to scan
+ * @return maximum device number found, or -ENODEV if none, or other -ve on
+ * error
+ */
+int blk_find_max_devnum(enum if_type if_type);
+
 #else
 #include <errno.h>
 /*