linux-kernel - Re: [PATCH v3 01/28] xhci: Add support to allocate several interrupters

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Date:   Mon, 13 Mar 2023 13:08:47 -0700
From:   Wesley Cheng <quic_wcheng@...cinc.com>
To:     Mathias Nyman <mathias.nyman@...ux.intel.com>,
        <srinivas.kandagatla@...aro.org>, <mathias.nyman@...el.com>,
        <perex@...ex.cz>, <broonie@...nel.org>, <lgirdwood@...il.com>,
        <krzysztof.kozlowski+dt@...aro.org>, <agross@...nel.org>,
        <Thinh.Nguyen@...opsys.com>, <bgoswami@...cinc.com>,
        <andersson@...nel.org>, <robh+dt@...nel.org>,
        <gregkh@...uxfoundation.org>, <tiwai@...e.com>
CC:     <linux-kernel@...r.kernel.org>, <linux-arm-msm@...r.kernel.org>,
        <alsa-devel@...a-project.org>, <devicetree@...r.kernel.org>,
        <linux-usb@...r.kernel.org>, <quic_jackp@...cinc.com>,
        <quic_plai@...cinc.com>
Subject: Re: [PATCH v3 01/28] xhci: Add support to allocate several
 interrupters

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@...ux.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