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From:   Shuah Khan <skhan@linuxfoundation.org>
To:     valentina.manea.m@gmail.com, shuah@kernel.org,
        gregkh@linuxfoundation.org
Cc:     Shuah Khan <skhan@linuxfoundation.org>, mailhol.vincent@wanadoo.fr,
        linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org,
        Hongren Zenithal Zheng <i@zenithal.me>,
        Alan Stern <stern@rowland.harvard.edu>
Subject: [PATCH] usbip: add USBIP_URB_* URB transfer flags
Date:   Tue, 16 Aug 2022 15:57:11 -0600
Message-Id: <20220816215711.55025-1-skhan@linuxfoundation.org>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

USBIP driver packs URB transfer flags in PDUs that are exchanged
between Server (usbip_host) and Clinet (vhci_hcd). URB_* flags
are internal to kernel and could change. Where as USBIP URB flags
exchanged in PDUs are USBIP user API must not change.

Add USBIP_URB* flags to make this an expclicit API and change the
client and server to map them. Details as follows:

Client tx path (USBIP_CMD_SUBMIT):
- Maps URB_* to USBIP_URB_* when it sends USBIP_CMD_SUBMIT packet.

Server rx path (USBIP_CMD_SUBMIT):
- Maps USBIP_URB_* to URB_* when it receives USBIP_CMD_SUBMIT packet.

Flags aren't included in USBIP_CMD_UNLINK and USBIP_RET_SUBMIT packets
and no special handling is needed for them in the following cases:

- Server rx path (USBIP_CMD_UNLINK)
- Client rx path & Server tx path (USBIP_RET_SUBMIT)

Update protocol documentation to reflect the change.

Suggested-by: Hongren Zenithal Zheng <i@zenithal.me>
Suggested-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
---
 Documentation/usb/usbip_protocol.rst | 11 ++--
 drivers/usb/usbip/stub_rx.c          |  8 ++-
 drivers/usb/usbip/usbip_common.c     | 95 +++++++++++++++++++++++++++-
 drivers/usb/usbip/vhci_tx.c          |  1 +
 drivers/usb/usbip/vudc_rx.c          |  1 +
 include/uapi/linux/usbip.h           | 40 ++++++++++++
 6 files changed, 146 insertions(+), 10 deletions(-)

diff --git a/Documentation/usb/usbip_protocol.rst b/Documentation/usb/usbip_protocol.rst
index 0b8541fda4d8..1c5b1db86fd0 100644
--- a/Documentation/usb/usbip_protocol.rst
+++ b/Documentation/usb/usbip_protocol.rst
@@ -341,12 +341,13 @@ USBIP_CMD_SUBMIT:
 +-----------+--------+---------------------------------------------------+
 | 0x14      | 4      | transfer_flags: possible values depend on the     |
 |           |        | URB transfer_flags (refer to URB doc in           |
+|           |        | include/uapi/linux/usbip.h and                    |
 |           |        | Documentation/driver-api/usb/URB.rst)             |
-|           |        | but with URB_NO_TRANSFER_DMA_MAP masked. Refer to |
-|           |        | function usbip_pack_cmd_submit and function       |
-|           |        | tweak_transfer_flags in drivers/usb/usbip/        |
-|           |        | usbip_common.c. The following fields may also ref |
-|           |        | to function usbip_pack_cmd_submit and URB doc     |
+|           |        | but with USBIP_URB_NO_TRANSFER_DMA_MAP masked.    |
+|           |        | Refer to usbip_pack_cmd_submit() and              |
+|           |        | tweak_transfer_flags() in drivers/usb/usbip/      |
+|           |        | usbip_common.c. The following fields may also     |
+|           |        | refer to usbip_pack_cmd_submit() and URB doc      |
 +-----------+--------+---------------------------------------------------+
 | 0x18      | 4      | transfer_buffer_length:                           |
 |           |        | use URB transfer_buffer_length                    |
diff --git a/drivers/usb/usbip/stub_rx.c b/drivers/usb/usbip/stub_rx.c
index 5dd41e8215e0..638d33120f26 100644
--- a/drivers/usb/usbip/stub_rx.c
+++ b/drivers/usb/usbip/stub_rx.c
@@ -464,7 +464,7 @@ static void stub_recv_cmd_submit(struct stub_device *sdev,
 	int nents;
 	int num_urbs = 1;
 	int pipe = get_pipe(sdev, pdu);
-	int use_sg = pdu->u.cmd_submit.transfer_flags & URB_DMA_MAP_SG;
+	int use_sg = pdu->u.cmd_submit.transfer_flags & USBIP_URB_DMA_MAP_SG;
 	int support_sg = 1;
 	int np = 0;
 	int ret, i;
@@ -514,7 +514,7 @@ static void stub_recv_cmd_submit(struct stub_device *sdev,
 				num_urbs = nents;
 				priv->completed_urbs = 0;
 				pdu->u.cmd_submit.transfer_flags &=
-								~URB_DMA_MAP_SG;
+								~USBIP_URB_DMA_MAP_SG;
 			}
 		} else {
 			buffer = kzalloc(buf_len, GFP_KERNEL);
@@ -556,6 +556,7 @@ static void stub_recv_cmd_submit(struct stub_device *sdev,
 			return;
 		}
 
+		/* Unpack the pdu to an urb (map USBIP_URB_* to URB_* flags) */
 		usbip_pack_pdu(pdu, priv->urbs[0], USBIP_CMD_SUBMIT, 0);
 	} else {
 		for_each_sg(sgl, sg, nents, i) {
@@ -566,6 +567,9 @@ static void stub_recv_cmd_submit(struct stub_device *sdev,
 			if (!priv->urbs[i])
 				goto err_urb;
 
+			/* Unpack the pdu to an urb (map USBIP_URB_* to
+			 * URB_* flags)
+			 */
 			usbip_pack_pdu(pdu, priv->urbs[i], USBIP_CMD_SUBMIT, 0);
 			priv->urbs[i]->transfer_buffer = sg_virt(sg);
 			priv->urbs[i]->transfer_buffer_length = sg->length;
diff --git a/drivers/usb/usbip/usbip_common.c b/drivers/usb/usbip/usbip_common.c
index 2ab99244bc31..bb0596588327 100644
--- a/drivers/usb/usbip/usbip_common.c
+++ b/drivers/usb/usbip/usbip_common.c
@@ -344,6 +344,95 @@ static unsigned int tweak_transfer_flags(unsigned int flags)
 	return flags;
 }
 
+/*
+ * USBIP driver packs URB transfer flags in PDUs that are exchanged
+ * between Server (usbip_host) and Client (vhci_hcd). URB_* flags
+ * are internal to kernel and could change. Where as USBIP URB flags
+ * exchanged in PDUs are USBIP user API must not change.
+ *
+ * USBIP_URB* flags are exported as explicit API and client and server
+ * do mapping from kernel flags to USBIP_URB*. Details as follows:
+ *
+ * Client tx path (USBIP_CMD_SUBMIT):
+ * - Maps URB_* to USBIP_URB_* when it sends USBIP_CMD_SUBMIT packet.
+ *
+ * Server rx path (USBIP_CMD_SUBMIT):
+ * - Maps USBIP_URB_* to URB_* when it receives USBIP_CMD_SUBMIT packet.
+ *
+ * Flags aren't included in USBIP_CMD_UNLINK and USBIP_RET_SUBMIT packets
+ * and no special handling is needed for them in the following cases:
+ * - Server rx path (USBIP_CMD_UNLINK)
+ * - Client rx path & Server tx path (USBIP_RET_SUBMIT)
+ *
+ * Code paths:
+ * usbip_pack_pdu() is the common routine that handles packing pdu from
+ * urb and unpack pdu to an urb.
+ *
+ * usbip_pack_cmd_submit() and usbip_pack_ret_submit() handle
+ * USBIP_CMD_SUBMIT and USBIP_RET_SUBMIT respectively.
+ *
+ * usbip_map_urb_to_usbip() and usbip_map_usbip_to_urb() are used
+ * by usbip_pack_cmd_submit() and usbip_pack_ret_submit() to map
+ * flags.
+ */
+
+struct urb_to_usbip_flags {
+	unsigned int urb_flag;
+	unsigned int usbip_flag;
+};
+
+#define NUM_USBIP_FLAGS	17
+
+static const struct urb_to_usbip_flags flag_map[NUM_USBIP_FLAGS] = {
+	{URB_SHORT_NOT_OK, USBIP_URB_SHORT_NOT_OK},
+	{URB_ISO_ASAP, USBIP_URB_ISO_ASAP},
+	{URB_NO_TRANSFER_DMA_MAP, USBIP_URB_NO_TRANSFER_DMA_MAP},
+	{URB_ZERO_PACKET, USBIP_URB_ZERO_PACKET},
+	{URB_NO_INTERRUPT, USBIP_URB_NO_INTERRUPT},
+	{URB_FREE_BUFFER, USBIP_URB_FREE_BUFFER},
+	{URB_DIR_IN, USBIP_URB_DIR_IN},
+	{URB_DIR_OUT, USBIP_URB_DIR_OUT},
+	{URB_DIR_MASK, USBIP_URB_DIR_MASK},
+	{URB_DMA_MAP_SINGLE, USBIP_URB_DMA_MAP_SINGLE},
+	{URB_DMA_MAP_PAGE, USBIP_URB_DMA_MAP_PAGE},
+	{URB_DMA_MAP_SG, USBIP_URB_DMA_MAP_SG},
+	{URB_MAP_LOCAL, USBIP_URB_MAP_LOCAL},
+	{URB_SETUP_MAP_SINGLE, USBIP_URB_SETUP_MAP_SINGLE},
+	{URB_SETUP_MAP_LOCAL, USBIP_URB_SETUP_MAP_LOCAL},
+	{URB_DMA_SG_COMBINED, USBIP_URB_DMA_SG_COMBINED},
+	{URB_ALIGNED_TEMP_BUFFER, USBIP_URB_ALIGNED_TEMP_BUFFER},
+};
+
+static unsigned int urb_to_usbip(unsigned int flags)
+{
+	unsigned int map_flags = 0;
+	int loop;
+
+	for (loop = 0; loop < NUM_USBIP_FLAGS; loop++) {
+		if (flags & flag_map[loop].urb_flag)
+			map_flags |= flag_map[loop].usbip_flag;
+	}
+	pr_debug("%s: flag = %u map_flags = %u\n", __func__,
+		 flags, map_flags);
+
+	return map_flags;
+}
+
+static unsigned int usbip_to_urb(unsigned int flags)
+{
+	unsigned int map_flags = 0;
+	int loop;
+
+	for (loop = 0; loop < NUM_USBIP_FLAGS; loop++) {
+		if (flags & flag_map[loop].usbip_flag)
+			map_flags |= flag_map[loop].urb_flag;
+	}
+	pr_debug("%s: flag = %u map_flags = %u\n", __func__,
+		 flags, map_flags);
+
+	return map_flags;
+}
+
 static void usbip_pack_cmd_submit(struct usbip_header *pdu, struct urb *urb,
 				  int pack)
 {
@@ -354,14 +443,14 @@ static void usbip_pack_cmd_submit(struct usbip_header *pdu, struct urb *urb,
 	 * will be discussed when usbip is ported to other operating systems.
 	 */
 	if (pack) {
-		spdu->transfer_flags =
-			tweak_transfer_flags(urb->transfer_flags);
+		/* map after tweaking the urb flags */
+		spdu->transfer_flags = urb_to_usbip(tweak_transfer_flags(urb->transfer_flags));
 		spdu->transfer_buffer_length	= urb->transfer_buffer_length;
 		spdu->start_frame		= urb->start_frame;
 		spdu->number_of_packets		= urb->number_of_packets;
 		spdu->interval			= urb->interval;
 	} else  {
-		urb->transfer_flags         = spdu->transfer_flags;
+		urb->transfer_flags         = usbip_to_urb(spdu->transfer_flags);
 		urb->transfer_buffer_length = spdu->transfer_buffer_length;
 		urb->start_frame            = spdu->start_frame;
 		urb->number_of_packets      = spdu->number_of_packets;
diff --git a/drivers/usb/usbip/vhci_tx.c b/drivers/usb/usbip/vhci_tx.c
index 0ae40a13a9fe..0cf3413ea32d 100644
--- a/drivers/usb/usbip/vhci_tx.c
+++ b/drivers/usb/usbip/vhci_tx.c
@@ -25,6 +25,7 @@ static void setup_cmd_submit_pdu(struct usbip_header *pdup,  struct urb *urb)
 		USBIP_DIR_IN : USBIP_DIR_OUT;
 	pdup->base.ep	     = usb_pipeendpoint(urb->pipe);
 
+	/* pack the pdu from urb. Map URB_* to USBIP_URB_* flags */
 	usbip_pack_pdu(pdup, urb, USBIP_CMD_SUBMIT, 1);
 
 	if (urb->setup_packet)
diff --git a/drivers/usb/usbip/vudc_rx.c b/drivers/usb/usbip/vudc_rx.c
index d4a2f30a7580..b0efd6e00e6b 100644
--- a/drivers/usb/usbip/vudc_rx.c
+++ b/drivers/usb/usbip/vudc_rx.c
@@ -26,6 +26,7 @@ static int alloc_urb_from_cmd(struct urb **urbp,
 	if (!urb)
 		goto err;
 
+	/* unpack the pdu to a urb. Map USBIP_URB_* to URB_* flags */
 	usbip_pack_pdu(pdu, urb, USBIP_CMD_SUBMIT, 0);
 
 	if (urb->transfer_buffer_length > 0) {
diff --git a/include/uapi/linux/usbip.h b/include/uapi/linux/usbip.h
index fd393d908d8a..22d25ebde0cc 100644
--- a/include/uapi/linux/usbip.h
+++ b/include/uapi/linux/usbip.h
@@ -24,4 +24,44 @@ enum usbip_device_status {
 	VDEV_ST_USED,
 	VDEV_ST_ERROR
 };
+
+/* USB URB Transfer flags:
+ *
+ * USBIP server and client (vchi) pack URBs in TCP packets.
+ *
+ * - Client (vhci) clears the DMA flag and sends it off to the server.
+ * - Server (usbip-host) masks some flags and re-submits client urb to
+ *   usbcore.
+ * - USBIP protocol has its own direction field and doesn't use URB_DIR_IN
+ *
+ * As a result of coying the transfer flags, they now have become part
+ * of the API. Any changes to kernel flags now impact the USBIP user-space.
+ * In addition, it will be compatibility problem between server and client.
+ * These defines aren't directly referenced and it is an obscure usage
+ * hidden away in the packets.
+ *
+ * Add code to translate the values between the numbers used in userspace
+ * and the numbers used in the kernel. This will help with any future
+ * changes to kernel flags breaking the API.
+ */
+
+#define USBIP_URB_SHORT_NOT_OK		0x0001
+#define USBIP_URB_ISO_ASAP		0x0002
+#define USBIP_URB_NO_TRANSFER_DMA_MAP	0x0004
+#define USBIP_URB_ZERO_PACKET		0x0040
+#define USBIP_URB_NO_INTERRUPT		0x0080
+#define USBIP_URB_FREE_BUFFER		0x0100
+#define USBIP_URB_DIR_IN		0x0200
+#define USBIP_URB_DIR_OUT		0
+#define USBIP_URB_DIR_MASK		USBIP_URB_DIR_IN
+
+#define USBIP_URB_DMA_MAP_SINGLE	0x00010000
+#define USBIP_URB_DMA_MAP_PAGE		0x00020000
+#define USBIP_URB_DMA_MAP_SG		0x00040000
+#define USBIP_URB_MAP_LOCAL		0x00080000
+#define USBIP_URB_SETUP_MAP_SINGLE	0x00100000
+#define USBIP_URB_SETUP_MAP_LOCAL	0x00200000
+#define USBIP_URB_DMA_SG_COMBINED	0x00400000
+#define USBIP_URB_ALIGNED_TEMP_BUFFER	0x00800000
+
 #endif /* _UAPI_LINUX_USBIP_H */
-- 
2.34.1