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Date: Fri, 27 Apr 2018 09:51:46 +0200 From: Peter Rosin <peda@...ntia.se> To: Andrzej Hajda <a.hajda@...sung.com>, linux-kernel@...r.kernel.org Cc: Archit Taneja <architt@...eaurora.org>, Laurent Pinchart <Laurent.pinchart@...asonboard.com>, David Airlie <airlied@...ux.ie>, Martin Donnelly <martin.donnelly@...com>, Martyn Welch <martyn.welch@...labora.co.uk>, Gustavo Padovan <gustavo@...ovan.org>, Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, Sean Paul <seanpaul@...omium.org>, Inki Dae <inki.dae@...sung.com>, Joonyoung Shim <jy0922.shim@...sung.com>, Seung-Woo Kim <sw0312.kim@...sung.com>, Kyungmin Park <kyungmin.park@...sung.com>, Kukjin Kim <kgene@...nel.org>, Krzysztof Kozlowski <krzk@...nel.org>, CK Hu <ck.hu@...iatek.com>, Philipp Zabel <p.zabel@...gutronix.de>, Matthias Brugger <matthias.bgg@...il.com>, Rob Clark <robdclark@...il.com>, Benjamin Gaignard <benjamin.gaignard@...aro.org>, Vincent Abriou <vincent.abriou@...com>, Jyri Sarha <jsarha@...com>, dri-devel@...ts.freedesktop.org, linux-arm-kernel@...ts.infradead.org, linux-samsung-soc@...r.kernel.org, linux-mediatek@...ts.infradead.org, linux-arm-msm@...r.kernel.org, freedreno@...ts.freedesktop.org, linux-renesas-soc@...r.kernel.org Subject: Re: [PATCH 00/24] device link, bridge supplier <-> drm device On 2018-04-27 09:37, Peter Rosin wrote: > On 2018-04-27 09:11, Andrzej Hajda wrote: >> Hi Peter, >> >> On 27.04.2018 00:31, Peter Rosin wrote: >>> Hi! >>> >>> It was noted by Russel King [1] that bridges (not using components) >>> might disappear unexpectedly if the owner of the bridge was unbound. >>> Jyri Sarha had previously noted the same thing with panels [2]. Jyri >>> came up with using device links to resolve the panel issue, which >>> was also my (independent) reaction to the note from Russel. >>> >>> This series builds up to the addition of that link in the last >>> patch, but in my opinion the other 23 patches do have merit on their >>> own. >>> >>> The last patch needs testing, while the others look trivial. That >>> said, I might have missed some subtlety. >> >> of_node is used as an identifier of the bridge in the kernel. If you >> replace it with device pointer there will be potential problem with >> devices having two or more bridges, how do you differentiate bridges if >> the owner is the same? If I remember correctly current bridge code does >> not allow to have multiple bridges in one device, but that should be >> quite easy to fix if necessary. After this change it will become more >> difficult. > > I don't see how it will be more difficult? > >> Anyway I remember discussion that in DT world bridge should be >> identified rather by of_graph port node, not by parent node as it is >> now. If you want to translate this relation to device owner, you should >> add also port number to have full identification of the bridge, ie pair >> (owner, port_number) would be equivalent of port node. > > You even state the trivial solution here, just add the port/endpoint ID > when/if it is needed. So, what is the significant difference? Or, since this is apparently a rare requirement, you could make the owners that do need it fix it themselves. E.g. by embedding the struct drm_bridge in another struct that contains the needed ID, and use container_of to get to that containing struct with the ID. Cheers, Peter
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