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Date: Thu, 25 Jul 2013 13:25:12 +0800
Message-ID: <CACVXFVNyFk0Zpi4tC0ENiq8RcrtrjYW-Dhs+A56+Pw4BKm8y8A@mail.gmail.com>
Subject: Re: [PATCH 1/1] TX throttling bug-fixing patch of AX88179_178A
From: Ming Lei <tom.leiming@gmail.com>
To: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Ben Hutchings <bhutchings@solarflare.com>,
        Oliver Neukum <oliver@neukum.org>,
        Grant Grundler <grundler@google.com>, Freddy Xin <freddy@asix.com.tw>,
        David Miller <davem@davemloft.net>, netdev <netdev@vger.kernel.org>,
        linux-usb@vger.kernel.org, LKML <linux-kernel@vger.kernel.org>,
        =?Big5?B?QVNJWCBMb3VpcyBbxKyrwrOwXQ==?= <louis@asix.com.tw>,
        Allan Chou <allan@asix.com.tw>
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On Thu, Jul 25, 2013 at 1:10 PM, Eric Dumazet <eric.dumazet@gmail.com> wrote:
> On Thu, 2013-07-25 at 10:28 +0800, Ming Lei wrote:
>
>>
>> It depends if size of sg buffer(except for last one) in the sg list can be
>> divided by usb endpoint's max packet size(512 or 1024), at least there
>> is the constraint:
>>
>> http://git.kernel.org/cgit/linux/kernel/git/gregkh/usb.git/commit/?h=usb-next&id=10e232c597ac757e7f8600649f7e872e86de190f
>>
>> I am wondering if network stack can meet that.  If not, it might be a
>> bit difficult
>> because lots of USB host controller don't support that, and driver may have
>> to support SG and non-SG at the same time for working well on all HCs.
>
> I do not see the problem.
>
> If one skb has 2 fragments of 32KB, couldn't they be split into 64 1K
> segments by the device driver ?

OK, if length of fragments of all SKBs from network stack can always guarantee
to be divided by 1024, that is fine,  seems I worry about too much, :-)

Thanks,
-- 
Ming Lei
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