[PATCH] drm/dp_mst: Correct the bug in drm_dp_update_payload_part1()

[Lin, Wayne]

> -----Original Message-----
> From: Lyude Paul <lyude at redhat.com>
> Sent: Tuesday, December 3, 2019 8:23 AM
> To: Lin, Wayne <Wayne.Lin at amd.com>; dri-devel at lists.freedesktop.org;
> amd-gfx at lists.freedesktop.org
> Cc: Kazlauskas, Nicholas <Nicholas.Kazlauskas at amd.com>; Wentland, Harry
> <Harry.Wentland at amd.com>; Zuo, Jerry <Jerry.Zuo at amd.com>
> Subject: Re: [PATCH] drm/dp_mst: Correct the bug in
> drm_dp_update_payload_part1()
> 
> On Mon, 2019-12-02 at 11:58 +0800, Wayne Lin wrote:
> > [Why]
> > If the payload_state is DP_PAYLOAD_DELETE_LOCAL in series, current
> > code doesn't delete the payload at current index and just move the
> > index to next one after shuffling payloads.
> >
> > [How]
> > After shuffling payloads, decide whether to move on index or not
> > according to payload_state of current payload.
> >
> > Signed-off-by: Wayne Lin <Wayne.Lin at amd.com>
> > ---
> >  drivers/gpu/drm/drm_dp_mst_topology.c | 3 ++-
> >  1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c
> > b/drivers/gpu/drm/drm_dp_mst_topology.c
> > index 81e92b260d7a..8da5d461ea01 100644
> > --- a/drivers/gpu/drm/drm_dp_mst_topology.c
> > +++ b/drivers/gpu/drm/drm_dp_mst_topology.c
> > @@ -3176,7 +3176,8 @@ int drm_dp_update_payload_part1(struct
> > drm_dp_mst_topology_mgr *mgr)
> >  			drm_dp_mst_topology_put_port(port);
> >  	}
> >
> > -	for (i = 0; i < mgr->max_payloads; i++) {
> > +	for (i = 0; i < mgr->max_payloads;
> > +		(mgr->payloads[i].payload_state == DP_PAYLOAD_DELETE_LOCAL) ?
> > i : i++) {
> 
> Took me a moment to figure out what this line was actually doing. Nice catch
> by the way!
> 
> Anyway: let's just drop this line to avoid making things confusing to read, drop
> i++ from the for loop instead, and just rewrite it so it looks like this:
> 
> for (i = 0; i < mgr->max_payloads; /* do nothing */) {
> 	if (mgr->payloads[i].payload_state != DP_PAYLOAD_DELETE_LOCAL) {
> 		i++;
> 		continue;
> 	}
> 
> With those changes, this patch is:
> 
> Reviewed-by: Lyude Paul <lyude at redhat.com>
> 

Thanks for your time and sorry for not well organized code.
I will send you the v2 right away. Thanks!
 
> I can go ahead and push these patches to drm-misc for you once you've sent
> me the v2
> >  		if (mgr->payloads[i].payload_state != DP_PAYLOAD_DELETE_LOCAL)
> >  			continue;
> >
> --
> Cheers,
> 	Lyude Paul
--
BR,
Wayne Lin