On 2018-05-23 14:38, Andrzej Hajda wrote: > On 23.05.2018 12:46, Peter Rosin wrote: >> On 2018-05-23 11:39, Andrzej Hajda wrote: >> >> *snip* >> >>> Panels are managed by dsi host only if dsi host implements it, and it is >>> up to dsi host author, it is not mandatory. The only case I am aware of >>> is exynos-dsi. I guess most developers are not aware of the problem, or >>> they do not care, or ... whatever. This patch shows it very clearly. >> *snip* >> >>> With such approach you do not protect dsi hosts without dynamic panel >>> management support. As I said earlier: it is matter of panel consumers >>> (for example dsi host), ie if it implements dynamic panel management, it >>> should attach panel without creating device_links, as it take care of >>> disappearing panels. If it does not perform dynamic management it should >>> rely on default behavior - links should be created, to protect drm >>> device from using dangling pointers. >> So, you're saying that the only place that needs to be patched to call >> drm_panel_attach_without_link is exynos_dsi_host_attach()? > > It should be at least there, but I suppose only there. > >> >> What about the dw-mipi-dsi driver in rockchip/dw-mipi-dsi.c? It also >> calls drm_panel_attach/drm_panel_detach in its dw_mipi_dsi_host_attach >> and dw_mipi_dsi_host_detach functions. > > dw_mipi_dsi_host_detach calls only drm_panel_detach, dangling pointer > will stay in dsi->panel, and nothing prevents from using it. I guess it > is just buggy code. Yeah, now I see it. >> >> Similar thing in bridge/synopsis/dw-mipi-dsi.c, but it calls the >> wrappers drm_panel_bridge_add/remove to create an implicit bridge >> that in turn handles the panel. So, do we need a to add a >> drm_panel_bridge_add_without_link too? > > Again looks like a buggy code, before panel removal it should be turned > off, it should be performed under lock,.... Yeah, that looks like crap code. >> >> What about tegra/dsi.c? It also calls drm_panel_attach in its >> tegra_dsi_host_attach function? But that one doesn't detach the >> panel in its tegra_dsi_host_detach. Is that a bug? > > Also looks like a bug, but this is dual-channel device so I am not so sure. It's very confusing and hard to get a grip on how things are supposed to be done when everything appears to be riddled with misunderstandings... While browsing the code base I originally thought many more sites needed the drm_panel_attach_without_link variant, but that appears to not be the case. Thanks for your patient explanations! Cheers, Peter _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
