Re: [PATCH 1/1] TX throttling bug-fixing patch of AX88179_178A

Ben Hutchings
2013-07-25T13:34:13Z

On Thu, 2013-07-25 at 13:25 +0800, Ming Lei wrote:
> 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, :-)

Not that I have any experience with USB drivers, but perhaps
usb_sg_init()?

Ben.

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Ben Hutchings, Staff Engineer, Solarflare
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