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Date:   Thu, 17 Feb 2022 16:28:48 +0100
From:   Greg KH <gregkh@linuxfoundation.org>
To:     Jing Leng <3090101217@zju.edu.cn>
Cc:     balbi@kernel.org, ruslan.bilovol@gmail.com,
        pavel.hofman@ivitera.com, linux-usb@vger.kernel.org,
        linux-kernel@vger.kernel.org, Jing Leng <jleng@ambarella.com>
Subject: Re: [PATCH] usb: gadget: f_uac1: add set requests support
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On Thu, Feb 17, 2022 at 09:42:00AM +0800, Jing Leng wrote:
> Hi Greg KH,
> 
> > So is this a bug in the Host side to not do stuff like this?  Why not
> > fix it there instead?
> > 
> > Where is the requirement that this command must be handled by the
> > device?
> > 
> 
> First we need to clarify two issues.
> 
> 1. Does the Ubuntu go beyond the UAC1 specification?
> No. 
> On page 66 of the UAC1 specification (
> https://www.usb.org/sites/default/files/audio10.pdf):
> The bRequest can be SET_CUR, SET_MIN, SET_MAX, SET_RES or SET_MEM.
> In most cases, only the CUR and MEM attribute will be supported for
> the Set request. However, this specification does not prevent a
> designer from making other attributes programmable.
> Supplement: Windows 10 only sends SET_CUR request.
> 
> 2. Does the old version kernel have the problem on the Ubuntu?
> NO. (e.g. linux-5.10)
> The problem is introduced by the following modification:
>     commit 0356e6283c7177391d144612f4b12986ed5c4f6e
>     Author: Ruslan Bilovol <ruslan.bilovol@gmail.com>
>     Date:   Mon Jul 12 14:55:29 2021 +0200
> 
>         usb: gadget: f_uac1: add volume and mute support

Then please add this commit id as a "Fixes:" tag in the changelog area.

thanks,

greg k-h