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

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Message-ID: <56abaf44.86c3.19362571bee.Coremail.18500469033@163.com>
Date: Mon, 25 Nov 2024 16:01:36 +0800 (CST)
From: "Dingyan Li" <18500469033@....com>
To: gregkh@...uxfoundation.org, stern@...land.harvard.edu
Cc: linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org, 
	usb-storage@...ts.one-eyed-alien.net
Subject: Re:[PATCH v1] usb: storage: add a macro for the upper limit of max
 LUN

Hi Experts,

Any thoughts on this patch?

Regards,


At 2024-10-30 16:38:58, "Dingyan Li" <18500469033@....com> wrote:
>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@....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