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-rw-r--r--include/linux/usb/storage.h8
1 files changed, 8 insertions, 0 deletions
diff --git a/include/linux/usb/storage.h b/include/linux/usb/storage.h
index 8539956bc2be..51be3bb8fccb 100644
--- a/include/linux/usb/storage.h
+++ b/include/linux/usb/storage.h
@@ -82,4 +82,12 @@ struct bulk_cs_wrap {
#define US_BULK_RESET_REQUEST 0xff
#define US_BULK_GET_MAX_LUN 0xfe
+/*
+ * If 4 LUNs are supported then the LUNs would be
+ * numbered from 0 to 3, and the return value for
+ * US_BULK_GET_MAX_LUN request would be 3. The valid
+ * LUN field is 4 bits wide, the upper limit is 0x0f.
+ */
+#define US_BULK_MAX_LUN_LIMIT 0x0f
+
#endif