[PATCH v1] usb: storage: add a macro for the upper limit of max LUN

[Dingyan Li]

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 <18500...@163.com>
---
drivers/usb/gadget/function/f_tcm.c | 8 ++------
drivers/usb/gadget/function/storage_common.h | 2 +-
drivers/usb/storage/transport.c | 8 ++------
include/linux/usb/storage.h | 8 ++++++++
4 files changed, 13 insertions(+), 13 deletions(-)

diff --git a/drivers/usb/gadget/function/f_tcm.c b/drivers/usb/gadget/function/f_tcm.c
index 15bb3aa12aa8..e1914b20f816 100644
--- 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 ced5d2b09234..11ac785d5eee 100644
--- 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 9d767f6bf722..e6bc8ecaecbb 100644
--- 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 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
--
2.25.1

[Dingyan Li]

Hi Experts,

Any thoughts on this patch?

Regards,

[Alan Stern]

On Mon, Nov 25, 2024 at 04:01:36PM +0800, Dingyan Li wrote:
> Hi Experts,
>
> Any thoughts on this patch?
>
> Regards,

It looks fine to me.

Reviewed-by: Alan Stern <st...@rowland.harvard.edu>

Alan Stern

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