usb: storage: add a macro for the upper limit of max LUN

The meaning of this value is already used in several places,
but with constant values and comments to explain it separately.
It's better to have a central place to do this then use the macro
in those places for better readability.

Signed-off-by: Dingyan Li <18500469033@163.com>
Reviewed-by: Alan Stern <stern@rowland.harvard.edu>
Link: https://lore.kernel.org/r/20241030083858.46907-1-18500469033@163.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/usb/gadget/function/f_tcm.c b/drivers/usb/gadget/function/f_tcm.c
index 15bb3aa12aa8b415ee2a35e1bc11b188596e9f50..e1914b20f816786ad83c439926f29c8c46dab677 100644 (file)
--- a/drivers/usb/gadget/function/f_tcm.c
+++ b/drivers/usb/gadget/function/f_tcm.c
@@ -441,14 +441,10 @@ static int usbg_bot_setup(struct usb_function *f,
                        pr_err("No LUNs configured?\n");
                        return -EINVAL;
                }
-               /*
-                * If 4 LUNs are present we return 3 i.e. LUN 0..3 can be
-                * accessed. The upper limit is 0xf
-                */
                luns--;
-               if (luns > 0xf) {
+               if (luns > US_BULK_MAX_LUN_LIMIT) {
                        pr_info_once("Limiting the number of luns to 16\n");
-                       luns = 0xf;
+                       luns = US_BULK_MAX_LUN_LIMIT;
                }
                ret_lun = cdev->req->buf;
                *ret_lun = luns;

diff --git a/drivers/usb/gadget/function/storage_common.h b/drivers/usb/gadget/function/storage_common.h
index ced5d2b09234dc09bd0cc0b873379d3c9c1cdbf2..11ac785d5eee2682b2aed0afb28b315dd0d87c04 100644 (file)
--- a/drivers/usb/gadget/function/storage_common.h
+++ b/drivers/usb/gadget/function/storage_common.h
@@ -131,7 +131,7 @@ static inline bool fsg_lun_is_open(struct fsg_lun *curlun)
 #define FSG_BUFLEN     ((u32)16384)
 
 /* Maximal number of LUNs supported in mass storage function */
-#define FSG_MAX_LUNS   16
+#define FSG_MAX_LUNS   (US_BULK_MAX_LUN_LIMIT + 1)
 
 enum fsg_buffer_state {
        BUF_STATE_SENDING = -2,

diff --git a/drivers/usb/storage/transport.c b/drivers/usb/storage/transport.c
index 9d767f6bf7225f830a71267c94c09f0b4d392bfa..e6bc8ecaecbb202714be69c6db6b0a4824de4855 100644 (file)
--- a/drivers/usb/storage/transport.c
+++ b/drivers/usb/storage/transport.c
@@ -1087,13 +1087,9 @@ int usb_stor_Bulk_max_lun(struct us_data *us)
        usb_stor_dbg(us, "GetMaxLUN command result is %d, data is %d\n",
                     result, us->iobuf[0]);
 
-       /*
-        * If we have a successful request, return the result if valid. The
-        * CBW LUN field is 4 bits wide, so the value reported by the device
-        * should fit into that.
-        */
+       /* If we have a successful request, return the result if valid. */
        if (result > 0) {
-               if (us->iobuf[0] < 16) {
+               if (us->iobuf[0] <= US_BULK_MAX_LUN_LIMIT) {
                        return us->iobuf[0];
                } else {
                        dev_info(&us->pusb_intf->dev,

diff --git a/include/linux/usb/storage.h b/include/linux/usb/storage.h
index 8539956bc2be1c81ffa0b5919017b1d1521a5e56..51be3bb8fccb2e5b649bac39f062d4734c3be704 100644 (file)
--- 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