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usb: dwc3: gadget: Fix TRB preparation during SG

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When scatter gather (SG) is used, multiple TRBs are prepared from one DWC3
request (dwc3_request). So while preparing TRBs, the 'last' flag should be set
only when it is the last TRB being prepared from the last dwc3_request entry.

The current implementation uses list_is_last to check if the dwc3_request is the
last entry from the request_list. However, list_is_last returns false for the
last entry too. This is because, while preparing the first TRB from a request,
the function dwc3_prepare_one_trb modifies the request's next and prev pointers
while moving the URB to req_queued. Hence, list_is_last always returns false no
matter what.

The correct way is not to access the modified pointers of dwc3_request but to
use list_empty macro instead.

Fixes: e5ba5ec833 (usb: dwc3: gadget: fix scatter gather implementation)
Signed-off-by: Amit Virdi <amit.virdi@st.com>
Cc: <stable@vger.kernel.org> # v3.9+
Signed-off-by: Felipe Balbi <balbi@ti.com>
This commit is contained in:
Amit Virdi 2015-01-13 14:27:20 +05:30 committed by Felipe Balbi
parent 90bdf403db
commit ec512fb8e5
1 changed files with 1 additions and 2 deletions
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3
drivers/usb/dwc3/gadget.c
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@ -882,8 +882,7 @@ static void dwc3_prepare_trbs(struct dwc3_ep *dep, bool starting)
if (i == (request->num_mapped_sgs - 1) ||
sg_is_last(s)) {
if (list_is_last(&req->list,
&dep->request_list))
if (list_empty(&dep->request_list))
last_one = true;
chain = false;
}