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> -----Original Message-----
> From: Jani Nikula <jani.nikula@xxxxxxxxx>
> Sent: Friday, June 9, 2023 4:53 PM
> To: Lin, Wayne <Wayne.Lin@xxxxxxx>; dri-devel@xxxxxxxxxxxxxxxxxxxxx;
> amd-gfx@xxxxxxxxxxxxxxxxxxxxx
> Cc: lyude@xxxxxxxxxx; ville.syrjala@xxxxxxxxxxxxxxx; imre.deak@xxxxxxxxx;
> Wentland, Harry <Harry.Wentland@xxxxxxx>; Zuo, Jerry
> <Jerry.Zuo@xxxxxxx>; stable@xxxxxxxxxxxxxxx
> Subject: RE: [PATCH v4] drm/dp_mst: Clear MSG_RDY flag before sending new
> message
>
> >> > bool *handled)
> >> > +int drm_dp_mst_hpd_irq_handle_event(struct
> drm_dp_mst_topology_mgr
> >> *mgr, const u8 *esi,
> >> > + u8 *ack, bool *handled)
> >> > {
> >> > int ret = 0;
> >> > int sc;
> >> > @@ -4078,18 +4089,47 @@ int drm_dp_mst_hpd_irq(struct
> >> drm_dp_mst_topology_mgr *mgr, u8 *esi, bool *handl
> >> > if (esi[1] & DP_DOWN_REP_MSG_RDY) {
> >> > ret = drm_dp_mst_handle_down_rep(mgr);
> >> > *handled = true;
> >> > + *ack |= DP_DOWN_REP_MSG_RDY;
> >>
> >> My idea was that esi and ack would be the same size buffers, so the
> >> caller wouldn't have to worry where exactly to point ack to.
> >>
> >> I think the asymmetry here is misleading, with ack and esi having to
> >> point at different locations.
> >>
> > Thanks, Jani.
> >
> > But Event status Indicator Files (DPCD 0x2000h ~ 0x21FFH) are not all
> > designed to be ack clear, e.g. esi[0] here. My thought is to be
> > precise about what is handled and what is going to be ack clear.
> > Otherwise, write ack[0] to DPCD 0x2002h is not reasonable.
>
> The point is that you have the same indexes everywhere, even if ack[0] ends
> up being unused.
>
> Handle esi[1] & DP_DOWN_REP_MSG_RDY, set ack[1] |=
> DP_DOWN_REP_MSG_RDY.
>
> Similar pattern everywhere, drm core and drivers. The only place that needs to
> know the difference is where the ack is written back to DPCD.
>
> If we end up adding more helpers for drm core handling ESI, we'll keep
> repeating the same pattern, instead of passing individual u8 acks everywhere,
> with the driver having to figure out what pointers to pass.
>
> BR,
> Jani.
Thanks, Jani.
Will update another version.
Regards,
Wayne
>
>
>
>
> --
> Jani Nikula, Intel Open Source Graphics Center
