Re: [PATCH v6 3/4] ALSA: usb-audio: qcom: tag sideband endpoints before ring allocation

[sashiko-bot@kernel.org]

> On kernels with a PAGE_SIZE larger than TRB_SEGMENT_SIZE,
> xhci_endpoint_init() allocates the ring segments of endpoints that have
> already been tagged via xhci_sideband_add_endpoint() with
> dma_alloc_coherent() instead of from the shared xhci->segment_pool, so
> the buffer reported to the ADSP over QMI is guaranteed to come from a
> page of its own.
> 
> xhci_sideband_add_endpoint() must therefore run before the endpoint's
> transfer ring is first allocated (i.e. before snd_usb_endpoint_prepare()
> triggers xhci_endpoint_init()) for that allocation to apply. Move the
> xhci_sideband_add_endpoint() calls out of uaudio_endpoint_setup() and
> into enable_audio_stream(), before snd_usb_endpoint_prepare() is called
> for the data and sync endpoints, and unwind them on the new error paths.
> 
> Now that its only caller tags the endpoint before the ring exists, have
> xhci_sideband_add_endpoint() return -EBUSY if the endpoint already has a
> transfer ring, so a sideband client that adds the endpoint too late gets
> an error instead of a ring that silently came from the shared pool.
> 
> At that point in the setup sequence dev->ep_in[]/ep_out[] are not yet
> populated, since the endpoint's altsetting has not been activated, so
> usb_pipe_endpoint() cannot be used to find the usb_host_endpoint. Add
> uaudio_find_host_endpoint(), which resolves it directly from the
> interface's altsetting descriptor table instead.
> 
> Assisted-by: Claude:claude-opus-5-5
> Signed-off-by: Wesley Cheng <wesley.cheng@oss.qualcomm.com>

Sashiko has reviewed this patch and found no issues.

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Sashiko AI review · https://sashiko.dev/#/patchset/20261109-16k_offload_v1_b4-v6-0-858c6e0e007d@oss.qualcomm.com?part=3