linux-kernel - Re: [PATCH] usb: dwc2: host: fix isoc urb actual length

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Message-ID: <410670D7E743164D87FA6160E7907A560113A3A07F@am04wembxa.internal.synopsys.com>
Date:   Mon, 6 Nov 2017 12:30:24 +0000
From:   Minas Harutyunyan <Minas.Harutyunyan@...opsys.com>
To:     wlf <wulf@...k-chips.com>,
        Minas Harutyunyan <Minas.Harutyunyan@...opsys.com>,
        William Wu <william.wu@...k-chips.com>,
        "John.Youn@...opsys.com" <John.Youn@...opsys.com>,
        "balbi@...nel.org" <balbi@...nel.org>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>
CC:     "heiko@...ech.de" <heiko@...ech.de>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "linux-rockchip@...ts.infradead.org" 
        <linux-rockchip@...ts.infradead.org>,
        "frank.wang@...k-chips.com" <frank.wang@...k-chips.com>,
        "huangtao@...k-chips.com" <huangtao@...k-chips.com>,
        "dianders@...gle.com" <dianders@...gle.com>,
        "daniel.meng@...k-chips.com" <daniel.meng@...k-chips.com>,
        "fml@...k-chips.com" <fml@...k-chips.com>
Subject: Re: [PATCH] usb: dwc2: host: fix isoc urb actual length

Hi William,

On 11/6/2017 2:08 PM, wlf wrote:
> Hi Minas,
> 
> 在 2017年11月06日 17:28, Minas Harutyunyan 写道:
>> Hi,
>>
>> On 11/6/2017 12:46 PM, William Wu wrote:
>>> The actual_length in dwc2_hcd_urb structure is used
>>> to indicate the total data length transferred so far,
>>> but in dwc2_update_isoc_urb_state(), it just updates
>>> the actual_length of isoc frame, and don't update the
>>> urb actual_length at the same time, this will cause
>>> device drivers working error which depend on the urb
>>> actual_length.
>>>
>>> we can easily find this issue if use an USB camera，
>>> the userspace use libusb to get USB data from kernel
>>> via devio driver.In usb devio driver, processcompl()
>>> function will process urb complete and copy data to
>>> userspace depending on urb actual_length.
>>>
>>> Let's update the urb actual_length if the isoc frame
>>> is valid.
>>>
>>> Signed-off-by: William Wu <william.wu@...k-chips.com>
>>> ---
>>>     drivers/usb/dwc2/hcd_intr.c | 2 ++
>>>     1 file changed, 2 insertions(+)
>>>
>>> diff --git a/drivers/usb/dwc2/hcd_intr.c b/drivers/usb/dwc2/hcd_intr.c
>>> index 28a8210..01b1e13 100644
>>> --- a/drivers/usb/dwc2/hcd_intr.c
>>> +++ b/drivers/usb/dwc2/hcd_intr.c
>>> @@ -580,6 +580,7 @@ static enum dwc2_halt_status dwc2_update_isoc_urb_state(
>>>     		frame_desc->status = 0;
>>>     		frame_desc->actual_length = dwc2_get_actual_xfer_length(hsotg,
>>>     					chan, chnum, qtd, halt_status, NULL);
>>> +		urb->actual_length += frame_desc->actual_length;
>>>     		break;
>>>     	case DWC2_HC_XFER_FRAME_OVERRUN:
>>>     		urb->error_count++;
>>> @@ -599,6 +600,7 @@ static enum dwc2_halt_status dwc2_update_isoc_urb_state(
>>>     		frame_desc->status = -EPROTO;
>>>     		frame_desc->actual_length = dwc2_get_actual_xfer_length(hsotg,
>>>     					chan, chnum, qtd, halt_status, NULL);
>>> +		urb->actual_length += frame_desc->actual_length;
>>>     
>>>     		/* Skip whole frame */
>>>     		if (chan->qh->do_split &&
>>>
>> According urb description in usb.h urb->actual_length used for non-iso
>> transfers:
>>
>> "@actual_length: This is read in non-iso completion functions, and ...
>>
>>     * ISO transfer status is reported in the status and actual_length fields
>>     * of the iso_frame_desc array, ...."
> Yes,  urb->actual_length is used for non-iso transfers.  And for ISO
> transfer,  the most
> usb class drivers can only use iso frame status and actual_length to
> handle usb data,
> like: kernel v4.4 drivers/media/usb/uvc/uvc_video.c
> 
> But the usb devio driver really need the urb actual_length in the
> processcompl() if
> handle ISO transfer, just as I mentioned in the commit message.
> 
> And I also found the same issue on raspberrypi board:
> https://urldefense.proofpoint.com/v2/url?u=https-3A__github.com_raspberrypi_linux_issues_903&d=DwIDaQ&c=DPL6_X_6JkXFx7AXWqB0tg&r=6z9Al9FrHR_ZqbbtSAsD16pvOL2S3XHxQnSzq8kusyI&m=v5ECJPMqgVerj8G74QqsTJ7jt-qDVbCVIq8jq_t245s&s=ArX8DL6fZL4p3dsOY5AstGDRguIB_c1GDuuhf49-ev8&e=
> 
> So do you think we need to fix the usb devio driver, rather than fix dwc2?
> I think maybe we can use urb actual length for ISO transfer, it seems that
> don't cause any side-effect.
Agree, should be no any side-effect.

> 
>>
>> Thanks,
>> Minas
>>
>>
>>
>>
>>
>>
>