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Date:   Tue, 20 Apr 2021 09:08:47 +0800
From:   Peter Chen <peter.chen@kernel.org>
To:     Pawel Laszczak <pawell@cadence.com>
Cc:     balbi@kernel.org, gregkh@linuxfoundation.org,
        ruslan.bilovol@gmail.com, jbrunet@baylibre.com,
        linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org,
        kurahul@cadence.com
Subject: Re: [PATCH 1/2] usb: gadget: f_uac2: Stop endpoint before enabling
 it.
Message-ID: <20210420010846.GA6408@nchen>
References: <20210419075053.28467-1-pawell@gli-login.cadence.com>
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On 21-04-19 09:50:53, Pawel Laszczak wrote:
> From: Pawel Laszczak <pawell@cadence.com>
> 
> Patch adds disabling endpoint before enabling it during changing
> alternate setting. Lack of this functionality causes that in some
> cases uac2 queue the same request multiple time.
> Such situation can occur when host send set interface with
> alternate setting 1 twice.
> 
> Signed-off-by: Pawel Laszczak <pawell@cadence.com>
> ---
>  drivers/usb/gadget/function/f_uac2.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/usb/gadget/function/f_uac2.c b/drivers/usb/gadget/function/f_uac2.c
> index 9cc5c512a5cd..7d20a9d8a1b4 100644
> --- a/drivers/usb/gadget/function/f_uac2.c
> +++ b/drivers/usb/gadget/function/f_uac2.c
> @@ -890,17 +890,17 @@ afunc_set_alt(struct usb_function *fn, unsigned intf, unsigned alt)
>  	if (intf == uac2->as_out_intf) {
>  		uac2->as_out_alt = alt;
>  
> +		u_audio_stop_capture(&uac2->g_audio);
> +
>  		if (alt)
>  			ret = u_audio_start_capture(&uac2->g_audio);
> -		else
> -			u_audio_stop_capture(&uac2->g_audio);
>  	} else if (intf == uac2->as_in_intf) {
>  		uac2->as_in_alt = alt;
>  
> +		u_audio_stop_playback(&uac2->g_audio);
> +
>  		if (alt)
>  			ret = u_audio_start_playback(&uac2->g_audio);
> -		else
> -			u_audio_stop_playback(&uac2->g_audio);
>  	} else {
>  		dev_err(dev, "%s:%d Error!\n", __func__, __LINE__);
>  		return -EINVAL;

To avoid this, you may use prm->ep_enabled to judge if the endpoint has
already enabled.

-- 

Thanks,
Peter Chen