Date:   Mon, 5 Sep 2022 18:35:04 -0400
From:   Alexander Aring <aahringo@...hat.com>
To:     Miquel Raynal <miquel.raynal@...tlin.com>
Cc:     Alexander Aring <alex.aring@...il.com>,
        Stefan Schmidt <stefan@...enfreihafen.org>,
        linux-wpan - ML <linux-wpan@...r.kernel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Eric Dumazet <edumazet@...gle.com>,
        Network Development <netdev@...r.kernel.org>,
        David Girault <david.girault@...vo.com>,
        Romuald Despres <romuald.despres@...vo.com>,
        Frederic Blain <frederic.blain@...vo.com>,
        Nicolas Schodet <nico@...fr.eu.org>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        werner@...esberger.net
Subject: Re: [PATCH wpan-next 01/20] net: mac802154: Allow the creation of
 coordinator interfaces

Hi,

On Sun, Sep 4, 2022 at 11:16 PM Miquel Raynal <miquel.raynal@...tlin.com> wrote:
>
> Hi Alexander,
>
> aahringo@...hat.com wrote on Sat, 3 Sep 2022 15:40:35 -0400:
>
> > Hi,
> >
> > On Sat, Sep 3, 2022 at 3:10 PM Alexander Aring <aahringo@...hat.com> wrote:
> > >
> > > On Sat, Sep 3, 2022 at 3:07 PM Alexander Aring <aahringo@...hat.com> wrote:
> > > >
> > > > Hi,
> > > >
> > > > On Sat, Sep 3, 2022 at 12:06 PM Miquel Raynal <miquel.raynal@...tlin.com> wrote:
> > > > ...
> > > > >
> > > > > On the Tx side, when sending eg. an association request or an
> > > > > association response, I must expect and wait for an ack. This is
> > > > > what I am struggling to do. How can I know that a frame which I just
> > > > > transmitted has been acked? Bonus points, how can I do that in such a
> > > > > way that it will work with other devices? (hints below)
> > > > >
> > > > > > AACK will send a back if a frame with ack request bit was received.
> > > > > >
> > > > > > > say in a commit) I have seen no further updates about it so I guess
> > > > > > > it's still not available. I don't see any other way to know if a
> > > > > > > frame's ack has been received or not reliably.
> > > > > >
> > > > > > You implemented it for the at86rf230 driver (the spi one which is what
> > > > > > also atusb uses). You implemented the
> > > > > >
> > > > > > ctx->trac = IEEE802154_NO_ACK;
> > > > > >
> > > > > > which signals the upper layer that if the ack request bit is set, that
> > > > > > there was no ack.
> > > > > >
> > > > > > But yea, there is a missing feature for atusb yet which requires
> > > > > > firmware changes as well.
> > > > >
> > > > > :'(
> > > >
> > > > There is a sequence handling in tx done on atusb firmware and I think
> > > > it should be pretty easy to add a byte for trac status.
> > > >
> > > > diff --git a/atusb/fw/mac.c b/atusb/fw/mac.c
> > > > index 835002c..156bd95 100644
> > > > --- a/atusb/fw/mac.c
> > > > +++ b/atusb/fw/mac.c
> > > > @@ -116,7 +116,7 @@ static void receive_frame(void)
> > > >
> > > >  static bool handle_irq(void)
> > > >  {
> > > > -       uint8_t irq;
> > > > +       uint8_t irq, data[2];
> > > >
> > > >         irq = reg_read(REG_IRQ_STATUS);
> > > >         if (!(irq & IRQ_TRX_END))
> > > > @@ -124,7 +124,15 @@ static bool handle_irq(void)
> > > >
> > > >         if (txing) {
> > > >                 if (eps[1].state == EP_IDLE) {
> > > > -                       usb_send(&eps[1], &this_seq, 1, tx_ack_done, NULL);
> > > > +                       data[0] = tx_ack_done;
> > > > +
> > > > +                       spi_begin();
> > > > +                       spi_io(REG_TRX_STATE);
> > > > +
> > > > +                       data[1] = spi_recv();
> > > > +                       spi_end();
> > >
> > > data[1] = reg_read(REG_TRX_STATE) as seen above for REG_IRQ_STATUS
> > > would be better here...
> > >
> >
> > after digging the code more, there is another queue case which we
> > should handle, also correct using buffer parameter instead of the
> > callback parameter which was stupid... However I think the direction
> > is clear. Sorry for the spam.
>
> Don't be, your feedback is just super useful.
>
> > diff --git a/atusb/fw/mac.c b/atusb/fw/mac.c
> > index 835002c..b52ba1a 100644
> > --- a/atusb/fw/mac.c
> > +++ b/atusb/fw/mac.c
> > @@ -32,7 +32,7 @@ static uint8_t tx_buf[MAX_PSDU];
> >  static uint8_t tx_size = 0;
> >  static bool txing = 0;
> >  static bool queued_tx_ack = 0;
> > -static uint8_t next_seq, this_seq, queued_seq;
> > +static uint8_t next_seq, this_seq, queued_seq, queued_tx_trac;
> >
> >
> >  /* ----- Receive buffer management ----------------------------------------- */
> > @@ -57,6 +57,7 @@ static void tx_ack_done(void *user);
> >  static void usb_next(void)
> >  {
> >         const uint8_t *buf;
> > +       uint8_t data[2];
> >
> >         if (rx_in != rx_out) {
> >                 buf = rx_buf[rx_out];
> > @@ -65,7 +66,9 @@ static void usb_next(void)
> >         }
> >
> >         if (queued_tx_ack) {
> > -               usb_send(&eps[1], &queued_seq, 1, tx_ack_done, NULL);
> > +               data[0] = queued_seq;
> > +               data[1] = queued_tx_trac;
> > +               usb_send(&eps[1], data, sizeof(data), tx_ack_done, NULL);

This is also broken, see below.

> >                 queued_tx_ack = 0;
> >         }
> >  }
> > @@ -116,7 +119,7 @@ static void receive_frame(void)
> >
> >  static bool handle_irq(void)
> >  {
> > -       uint8_t irq;
> > +       uint8_t irq, data[2];
>
> I don't know why, but defining data on the stack just does not work.
> Defining it above with the other static variables is okay. I won't
> fight more for "today" but if someone has an explanation I am all hears.

I can explain it... following the usb_send() it will end in usb_io()
and this is an asynchronous function to use somehow the USB IP core
API of the mcu... it's wrong to use a stack variable here because it
can be overwritten. I am sorry, I did not keep that in mind...

- Alex

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