Re: [PATCH v2 1/3] Revert "usb: gadget: u_audio: add real feedback implementation"

Greg Kroah-Hartman
2021-08-27T08:29:16Z

On Thu, Aug 26, 2021 at 08:57:37PM +0200, Ferry Toth wrote:
> This reverts commit e89bb4288378b85c82212b60dc98ecda6b3d3a70.
>
> The commit is part of a series with commit
> 24f779dac8f3efb9629adc0e486914d93dc45517 causing a BUG on dwc3
> hardware, at least on Intel Merrifield platform when configured
> through configfs:
> BUG: kernel NULL pointer dereference, address: 0000000000000008
> ...
> RIP: 0010:dwc3_gadget_del_and_unmap_request+0x19/0xe0
> ...
> Call Trace:
> dwc3_remove_requests.constprop.0+0x12f/0x170
> __dwc3_gadget_ep_disable+0x7a/0x160
> dwc3_gadget_ep_disable+0x3d/0xd0
> usb_ep_disable+0x1c/0x70
> u_audio_stop_capture+0x79/0x120 [u_audio]
> afunc_set_alt+0x73/0x80 [usb_f_uac2]
> composite_setup+0x224/0x1b90 [libcomposite]
>
> Pavel's suggestion to add
> `echo "adaptive" > functions/uac2.usb0/c_sync` to the configfs script
> resolves the issue.
> Thinh suggests "the crash is probably because of f_uac2 prematurely
> freeing feedback request before its completion. usb_ep_dequeue() is
> asynchronous. dwc2() may treat it as a synchronous call so you didn't
> get a crash."
>
> Revert as this is a regression and the kernel shouldn't crash depending
> on configuration parameters.

Are these normal configuration options in the wild, or is this just
something that you "can do"?

> Signed-off-by: Ferry Toth <ftoth@exalondelft.nl>

I need an ack from the original authors to revert all this...

thanks,

greg k-h