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Date:   Tue, 16 Jun 2020 10:02:46 -0400
From:   Alan Stern <stern@rowland.harvard.edu>
To:     Macpaul Lin <macpaul.lin@mediatek.com>
Cc:     Chunfeng Yun <chunfeng.yun@mediatek.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Felipe Balbi <balbi@kernel.org>,
        Matthias Brugger <matthias.bgg@gmail.com>,
        =?utf-8?B?TWljaGHFgiBNaXJvc8WCYXc=?= <mirq-linux@rere.qmqm.pl>,
        Sergey Organov <sorganov@gmail.com>,
        Fabrice Gasnier <fabrice.gasnier@st.com>,
        linux-usb@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        linux-mediatek@lists.infradead.org, linux-kernel@vger.kernel.org,
        Mediatek WSD Upstream <wsd_upstream@mediatek.com>,
        Macpaul Lin <macpaul.lin@gmail.com>
Subject: Re: [PATCH 1/2] usb: gadget: introduce flag for large request
Message-ID: <20200616140246.GA30975@rowland.harvard.edu>
References: <1592310884-4307-1-git-send-email-macpaul.lin@mediatek.com>
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On Tue, Jun 16, 2020 at 08:34:43PM +0800, Macpaul Lin wrote:
> Some USB hardware like DMA engine can help to process (split) the data
> of each URB request into small packets. For example, the max packet size
> of high speed is 512 bytes. These kinds of hardware can help to split
> the continue Tx/Rx data requests into packets just at the max packet
> size during transmission. Hence upper layer software can reduce some
> effort for queueing many requests back and forth for larger data.
> 
> Here we introduce "can_exceed_maxp" flag in gadget when these kinds of
> hardware is ready to support these operations.

This isn't needed.  All UDC drivers must be able to support requests that 
are larger than the maxpacket size.

Alan Stern