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Message-ID: <e1203849-01b4-b196-36f3-76d58dd7c724@quicinc.com>
Date:   Tue, 27 Dec 2022 13:07:45 -0800
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Subject: Re: [RFC PATCH 06/14] usb: core: hcd: Introduce USB HCD APIs for
 interrupter management
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To:     Alan Stern <stern@rowland.harvard.edu>
CC:     <srinivas.kandagatla@linaro.org>, <mathias.nyman@intel.com>,
        <perex@perex.cz>, <broonie@kernel.org>, <lgirdwood@gmail.com>,
        <andersson@kernel.org>, <krzysztof.kozlowski+dt@linaro.org>,
        <gregkh@linuxfoundation.org>, <Thinh.Nguyen@synopsys.com>,
        <bgoswami@quicinc.com>, <tiwai@suse.com>, <robh+dt@kernel.org>,
        <agross@kernel.org>, <linux-kernel@vger.kernel.org>,
        <linux-arm-msm@vger.kernel.org>, <alsa-devel@alsa-project.org>,
        <devicetree@vger.kernel.org>, <linux-usb@vger.kernel.org>,
        <quic_jackp@quicinc.com>, <quic_plai@quicinc.com>
References: <20221223233200.26089-1-quic_wcheng@quicinc.com>
 <20221223233200.26089-7-quic_wcheng@quicinc.com>
 <Y6ca8IKLK9g497Qv@rowland.harvard.edu>
From:   Wesley Cheng <quic_wcheng@quicinc.com>
In-Reply-To: <Y6ca8IKLK9g497Qv@rowland.harvard.edu>
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Hi Alan,

On 12/24/2022 7:29 AM, Alan Stern wrote:
> On Fri, Dec 23, 2022 at 03:31:52PM -0800, Wesley Cheng wrote:
>> For USB HCDs that can support multiple USB interrupters, expose functions
>> that class drivers can utilize for setting up secondary interrupters.
>> Class drivers can pass this information to its respective clients, i.e.
>> a dedicated DSP.
>>
>> Signed-off-by: Wesley Cheng <quic_wcheng@quicinc.com>
>> ---
>>   drivers/usb/core/hcd.c  | 86 +++++++++++++++++++++++++++++++++++++++++
>>   include/linux/usb.h     |  7 ++++
>>   include/linux/usb/hcd.h | 16 +++++++-
>>   3 files changed, 108 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/usb/core/hcd.c b/drivers/usb/core/hcd.c
>> index 8300baedafd2..90ead90faf1d 100644
>> --- a/drivers/usb/core/hcd.c
>> +++ b/drivers/usb/core/hcd.c
> 
>> +/**
>> + * usb_hcd_stop_endpoint - Halt USB EP transfers
>> + * @udev: usb device
>> + * @ep: usb ep to stop
>> + *
>> + * Stop pending transfers on a specific USB endpoint.
>> + **/
>> +int usb_hcd_stop_endpoint(struct usb_device *udev,
>> +					struct usb_host_endpoint *ep)
>> +{
>> +	struct usb_hcd *hcd = bus_to_hcd(udev->bus);
>> +	int ret = 0;
>> +
>> +	if (hcd->driver->stop_endpoint)
>> +		ret = hcd->driver->stop_endpoint(hcd, udev, ep);
>> +
>> +	return ret;
>> +}
>> +EXPORT_SYMBOL_GPL(usb_hcd_stop_endpoint);
> 
> You know, there already is a function that does this.  It's named
> usb_hcd_flush_endpoint().  No need to add another function that does the
> same thing.
> 

Thanks for the suggestion and review.

Hmmm...maybe I should change the name of the API then to avoid the 
confusion.  Yes, usb_hcd_flush_endpoint() does ensure that URBs 
submitted to the EP are stopped.  However, with this offloading concept, 
we aren't actually submitting URBs from the main processor, so the 
ep->urb_list will be empty.

This means the usb_hcd_flush_endpoint() API won't actually do anything. 
  What we need is to ensure that we send a XHCI stop ep command to the 
controller.

Thanks
Wesley Cheng