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

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Message-ID: <a45ff335-0563-85c7-3b31-d6ca23a54a3f@linux.intel.com>
Date:   Fri, 10 Mar 2023 17:07:35 +0200
From:   Mathias Nyman <mathias.nyman@...ux.intel.com>
To:     Wesley Cheng <quic_wcheng@...cinc.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

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.

> Signed-off-by: Mathias Nyman <mathias.nyman@...ux.intel.com>
> Signed-off-by: Wesley Cheng <quic_wcheng@...cinc.com>

My Signed-off-by tag is being misused here.

I wrote a chunk of the code in this patch as PoC that I shared in a separate topic branch.
It was incomplete and not intended for upstream yet. (lacked locking, several fixme parts, etc..)
The rest of the code in this patch is completely new to me.

Thanks
-Mathias