linux-kernel - Re: [PATCH 1/2] usbip: fix off-by-one frame number calculation

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Message-id: <3dde28df-64d5-4b2e-f044-04e73b3fb156@samsung.com>
Date:   Tue, 07 Nov 2017 12:21:19 +0100
From:   Krzysztof Opasiak <k.opasiak@...sung.com>
To:     Arnd Bergmann <arnd@...db.de>,
        Valentina Manea <valentina.manea.m@...il.com>,
        Shuah Khan <shuah@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Johan Hovold <johan@...nel.org>, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] usbip: fix off-by-one frame number calculation



On 11/07/2017 11:39 AM, Arnd Bergmann wrote:
> vgadget_get_frame returns a frame number from 0 to 2046, which
> may require an expensive division operation to wrap at one lower
> than the usual number.
> 
> I can't see any reason for this, and all other drivers wrap at
> a power-of-two number. My best explanation is that it was a simple
> typo, so I'm changing the % modulo operator into a cheaper bitmask
> that the other drivers use, to make it wrap after 0x7ff rather than
> before it.
> 
> Signed-off-by: Arnd Bergmann <arnd@...db.de>

Looks good to me:
Reviewed-by: Krzysztof Opasiak <k.opasiak@...sung.com>

-- 
Krzysztof Opasiak
Samsung R&D Institute Poland
Samsung Electronics