> Date: Fri, 7 Oct 2016 08:33:06 +0200
> From: Stefan Sperling <[email protected]>
>
> On Thu, Oct 06, 2016 at 06:51:04PM +0200, Stefan Sperling wrote:
> > athn(4) has a hack which disables lower Tx retry rates if RTS is used.
> >
> > I don't understand why this was added. Perhaps the assumption was
> > that RTS will prevent transmission failures outright.
>
> I believe I've found the reason for this after examining the frame
> exchanges more closely. OK to commit these comments instead?
>
> The duration field mentioned below specifies the air time required
> to send the data frame + ack. And of course different data rates
> use up different amounts of air time.
Not to familliar with the specs, but you explanation Sounds plausible.
I wouldn't hesitate to commit this.
> Index: ar5008.c
> ===================================================================
> RCS file: /cvs/src/sys/dev/ic/ar5008.c,v
> retrieving revision 1.35
> diff -u -p -r1.35 ar5008.c
> --- ar5008.c 5 Jan 2016 18:41:15 -0000 1.35
> +++ ar5008.c 7 Oct 2016 06:26:03 -0000
> @@ -1467,8 +1467,12 @@ ar5008_tx(struct athn_softc *sc, struct
> ds->ds_ctl0 |= AR_TXC0_CTS_ENABLE;
> }
> }
> + /*
> + * Disable multi-rate retries when protection is used.
> + * The RTS/CTS frame's duration field is fixed and won't be
> + * updated by hardware when the data rate changes.
> + */
> if (ds->ds_ctl0 & (AR_TXC0_RTS_ENABLE | AR_TXC0_CTS_ENABLE)) {
> - /* Disable multi-rate retries when protection is used. */
> ridx[1] = ridx[2] = ridx[3] = ridx[0];
> }
> /* Setup multi-rate retries. */
> Index: ar9003.c
> ===================================================================
> RCS file: /cvs/src/sys/dev/ic/ar9003.c,v
> retrieving revision 1.39
> diff -u -p -r1.39 ar9003.c
> --- ar9003.c 5 Jan 2016 18:41:15 -0000 1.39
> +++ ar9003.c 7 Oct 2016 06:26:18 -0000
> @@ -1613,8 +1613,12 @@ ar9003_tx(struct athn_softc *sc, struct
> ds->ds_ctl11 |= AR_TXC11_CTS_ENABLE;
> }
> }
> + /*
> + * Disable multi-rate retries when protection is used.
> + * The RTS/CTS frame's duration field is fixed and won't be
> + * updated by hardware when the data rate changes.
> + */
> if (ds->ds_ctl11 & (AR_TXC11_RTS_ENABLE | AR_TXC11_CTS_ENABLE)) {
> - /* Disable multi-rate retries when protection is used. */
> ridx[1] = ridx[2] = ridx[3] = ridx[0];
> }
> /* Setup multi-rate retries. */
>
>
>
