Message-ID: <6024f762-6085-10cd-e73a-9031722b2334@quicinc.com>
Date:   Mon, 13 Mar 2023 13:08:47 -0700
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Subject: Re: [PATCH v3 01/28] xhci: Add support to allocate several
 interrupters
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To:     Mathias Nyman <mathias.nyman@linux.intel.com>,
        <srinivas.kandagatla@linaro.org>, <mathias.nyman@intel.com>,
        <perex@perex.cz>, <broonie@kernel.org>, <lgirdwood@gmail.com>,
        <krzysztof.kozlowski+dt@linaro.org>, <agross@kernel.org>,
        <Thinh.Nguyen@synopsys.com>, <bgoswami@quicinc.com>,
        <andersson@kernel.org>, <robh+dt@kernel.org>,
        <gregkh@linuxfoundation.org>, <tiwai@suse.com>
CC:     <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: <20230308235751.495-1-quic_wcheng@quicinc.com>
 <20230308235751.495-2-quic_wcheng@quicinc.com>
 <a45ff335-0563-85c7-3b31-d6ca23a54a3f@linux.intel.com>
From:   Wesley Cheng <quic_wcheng@quicinc.com>
In-Reply-To: <a45ff335-0563-85c7-3b31-d6ca23a54a3f@linux.intel.com>
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Hi Mathias,

On 3/10/2023 7:07 AM, Mathias Nyman wrote:
> On 9.3.2023 1.57, Wesley Cheng wrote:
>> From: Mathias Nyman <mathias.nyman@linux.intel.com>
>>
>> Introduce xHCI APIs to allow for clients to allocate and free
>> interrupters.  This allocates an array of interrupters, which is based on
>> the max_interrupters parameter.  The primary interrupter is set as the
>> first entry in the array, and secondary interrupters following after.
>>
> 
> I'm thinking about changing this offloading xHCI API
> xhci should be aware and keep track of which devices and endpoints that
> are offloaded to avoid device getting offloaded twice, avoid xhci driver
> from queuing anything itself for these, and act properly if the offloaded
> device or entire host is removed.
> 
> So first thing audio side would need to do do is register/create an
> offload entry for the device using the API:
> 
> struct xhci_sideband *xhci_sideband_register(struct usb_device *udev)
> 
> (xHCI specs calls offload sideband)
> Then endpoints and interrupters can be added and removed from this
> offload entry
> 
> I have some early thoughts written as non-compiling code in:
> 
> git://git.kernel.org/pub/scm/linux/kernel/git/mnyman/xhci.git 
> feature_interrupters
> https://git.kernel.org/pub/scm/linux/kernel/git/mnyman/xhci.git/log/?h=feature_interrupters 
> 
> 
> Let me know what you think about this.
> 

The concept/framework you built looks good to me.  Makes sense to have 
XHCI better maintain the offloading users.  One thing I would request is 
to move xhci-sideband.h to the include directory since the class driver 
levels would need to be able to reference the structure and APIs you've 
exposed.

I have yet to try it with our implementation, but I'll work on plugging 
it in and fix any issues I see along the way.

Thanks
Wesley Cheng