[PATCH v2 21/25] usb: gadget: f_tcm: Get stream by tag

[Thinh Nguyen]

In preparation for TASK MANAGEMENT handling of overlapped command,
implement uasp_get_stream_by_tag() to find the active stream/command
based on a given tag.

For simplicity, we use mod operation to quickly find an in-progress
matching command tag to check for overlapped command. The assumption is
that the UASP class driver will limit to using tag id from 1 to
USBG_NUM_CMDS. This is based on observation from the Windows and Linux
UASP storage class driver behavior. If an unusual UASP class driver uses
a tag greater than USBG_NUM_CMDS, then this method may no longer work
due to possible stream id collision. In that case, we need to use a
proper algorithm to fetch the stream (or simply walk through all active
streams to check for overlap).

Signed-off-by: Thinh Nguyen <Thinh.Nguyen@xxxxxxxxxxxx>
---
 Changes in v2:
 - Splitted from TASK MANAGEMENT change

 drivers/usb/gadget/function/f_tcm.c | 30 ++++++++++++++++++++++-------
 1 file changed, 23 insertions(+), 7 deletions(-)

diff --git a/drivers/usb/gadget/function/f_tcm.c b/drivers/usb/gadget/function/f_tcm.c
index 084143213176..a10e74290664 100644
--- a/drivers/usb/gadget/function/f_tcm.c
+++ b/drivers/usb/gadget/function/f_tcm.c
@@ -506,6 +506,22 @@ static void uasp_cleanup_old_alt(struct f_uas *fu)
 	uasp_free_cmdreq(fu);
 }
 
+static struct uas_stream *uasp_get_stream_by_tag(struct f_uas *fu, u16 tag)
+{
+	/*
+	 * For simplicity, we use mod operation to quickly find an in-progress
+	 * matching command tag to check for overlapped command. The assumption
+	 * is that the UASP class driver will limit to using tag id from 1 to
+	 * USBG_NUM_CMDS. This is based on observation from the Windows and
+	 * Linux UASP storage class driver behavior. If an unusual UASP class
+	 * driver uses a tag greater than USBG_NUM_CMDS, then this method may no
+	 * longer work due to possible stream id collision. In that case, we
+	 * need to use a proper algorithm to fetch the stream (or simply walk
+	 * through all active streams to check for overlap).
+	 */
+	return &fu->stream[tag % USBG_NUM_CMDS];
+}
+
 static void uasp_status_data_cmpl(struct usb_ep *ep, struct usb_request *req);
 
 static int uasp_prepare_r_request(struct usbg_cmd *cmd)
@@ -513,7 +529,7 @@ static int uasp_prepare_r_request(struct usbg_cmd *cmd)
 	struct se_cmd *se_cmd = &cmd->se_cmd;
 	struct f_uas *fu = cmd->fu;
 	struct usb_gadget *gadget = fuas_to_gadget(fu);
-	struct uas_stream *stream = cmd->stream;
+	struct uas_stream *stream = uasp_get_stream_by_tag(fu, cmd->tag);
 
 	if (!gadget->sg_supported) {
 		cmd->data_buf = kmalloc(se_cmd->data_length, GFP_ATOMIC);
@@ -546,7 +562,7 @@ static void uasp_prepare_status(struct usbg_cmd *cmd)
 {
 	struct se_cmd *se_cmd = &cmd->se_cmd;
 	struct sense_iu *iu = &cmd->sense_iu;
-	struct uas_stream *stream = cmd->stream;
+	struct uas_stream *stream = uasp_get_stream_by_tag(cmd->fu, cmd->tag);
 
 	cmd->state = UASP_QUEUE_COMMAND;
 	iu->iu_id = IU_ID_STATUS;
@@ -568,8 +584,8 @@ static void uasp_prepare_status(struct usbg_cmd *cmd)
 static void uasp_status_data_cmpl(struct usb_ep *ep, struct usb_request *req)
 {
 	struct usbg_cmd *cmd = req->context;
-	struct uas_stream *stream = cmd->stream;
 	struct f_uas *fu = cmd->fu;
+	struct uas_stream *stream = uasp_get_stream_by_tag(fu, cmd->tag);
 	int ret;
 
 	if (req->status == -ESHUTDOWN)
@@ -620,7 +636,7 @@ static void uasp_status_data_cmpl(struct usb_ep *ep, struct usb_request *req)
 static int uasp_send_status_response(struct usbg_cmd *cmd)
 {
 	struct f_uas *fu = cmd->fu;
-	struct uas_stream *stream = cmd->stream;
+	struct uas_stream *stream = uasp_get_stream_by_tag(fu, cmd->tag);
 	struct sense_iu *iu = &cmd->sense_iu;
 
 	iu->tag = cpu_to_be16(cmd->tag);
@@ -632,7 +648,7 @@ static int uasp_send_status_response(struct usbg_cmd *cmd)
 static int uasp_send_read_response(struct usbg_cmd *cmd)
 {
 	struct f_uas *fu = cmd->fu;
-	struct uas_stream *stream = cmd->stream;
+	struct uas_stream *stream = uasp_get_stream_by_tag(fu, cmd->tag);
 	struct sense_iu *iu = &cmd->sense_iu;
 	int ret;
 
@@ -675,7 +691,7 @@ static int uasp_send_read_response(struct usbg_cmd *cmd)
 static int uasp_send_write_request(struct usbg_cmd *cmd)
 {
 	struct f_uas *fu = cmd->fu;
-	struct uas_stream *stream = cmd->stream;
+	struct uas_stream *stream = uasp_get_stream_by_tag(fu, cmd->tag);
 	struct sense_iu *iu = &cmd->sense_iu;
 	int ret;
 
@@ -1285,7 +1301,7 @@ static void usbg_aborted_task(struct se_cmd *se_cmd)
 {
 	struct usbg_cmd *cmd = container_of(se_cmd, struct usbg_cmd, se_cmd);
 	struct f_uas *fu = cmd->fu;
-	struct uas_stream *stream = cmd->stream;
+	struct uas_stream *stream = uasp_get_stream_by_tag(fu, cmd->tag);
 	int ret = 0;
 
 	if (stream->req_out->status == -EINPROGRESS)
-- 
2.28.0