netdev - Re: [PATCH] Check for SKBTX_HW

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Message-ID: <CAFcVECK69W0Ru83=GsjxfcCRp7x4Li139NUPCpVo86fKP-r1ig@mail.gmail.com>
Date:   Wed, 13 Mar 2019 11:29:59 +0530
From:   Harini Katakam <harinik@...inx.com>
To:     "Keller, Jacob E" <jacob.e.keller@...el.com>
Cc:     Paul Thomas <pthomas8589@...il.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH] Check for SKBTX_HW_TSTAMP in macb driver

Hi Paul, Jake,
On Wed, Mar 13, 2019 at 3:08 AM Keller, Jacob E
<jacob.e.keller@...el.com> wrote:
>
>
>
> > -----Original Message-----
> > From: netdev-owner@...r.kernel.org [mailto:netdev-owner@...r.kernel.org] On
> > Behalf Of Paul Thomas
> > Sent: Tuesday, March 12, 2019 1:05 PM
> > To: netdev@...r.kernel.org
> > Subject: Re: [PATCH] Check for SKBTX_HW_TSTAMP in macb driver
> >
> > On Tue, Mar 12, 2019 at 3:51 PM Paul Thomas <pthomas8589@...il.com> wrote:
> > >
<snip>
> > >                         /* First, update TX stats if needed */
> > >                         if (skb) {
> > > -                               if (gem_ptp_do_txstamp(queue, skb, desc) == 0) {
> > > -                                       /* skb now belongs to timestamp buffer
> > > -                                        * and will be removed later
> > > -                                        */
> > I think the above does the same thing as if CONFIG_MACB_USE_HWSTAMP is
> > undefined regarding cleanup, so there is no extra cleanup if the
> > gem_ptp_do_txstamp() path isn't taken, but I wasn't sure about the
> > "skb now belongs to the timestamp buffer" if we don't go down that
> > path.
>
> The path they're taking here seems a bit weird... I suspect the function gem_ptp_do_txstamp is doing something.
>
> Normally the driver should use something like skb_get to obtain a reference to the skb.

Just FYI, this is the historical reason for the skb implementation here:
https://patchwork.kernel.org/patch/9473937/

Regards,
Harini