Hello,
This is a new attempt at fixing the "panel is missing" issue (described in this thread [1]). I lost track of Eric's proposal, but I recently proposed to address this problem through a new ->detect() hook in the panel_funcs interface [2], which was rejected.
So here is a new version based on the feedback I had from Daniel, Thierry and Rob.
The idea is to allow of_drm_find_panel() to return -ENODEV and let the DRM driver decide what to do with that (silently ignore the missing component and register the DRM device, or fail to register the DRM device).
Patch 1 is just a fix for an OF node ref leak I found in the tegra driver while working on this patch series. It can be applied independently but I send it here since patch 2 depends on it.
Patch 2 changes the semantic of of_drm_find_panel() so that it returns an ERR_PTR() instead of NULL when the panel is not found. This way we'll be able to differentiate the "panel is missing" from "panel has not been probed yet" errors.
Patch 3 and 4 are adding new tests in of_drm_find_panel() and drm_of_find_panel_or_bridge() to return -ENODEV when the status property of the DT node is not set to "okay".
Patch 5 is patching the VC4 DSI encoder driver to gracefully handle the -ENODEV case and allow the registration of the DRM device when the DSI device is disabled.
And finally, patch 6 is modifying the rpi-touchscreen panel driver to update the status property of the DT node when the device is not reachable on the I2C bus. This way, the DSI encoder driver will get an -ENODEV and the DRM device will be registered even if the DSI panel is not connected. Note that the status prop update is currently done in the I2C driver instead of the I2C or device-model core because I think modifying the behavior for all I2C devices (or all devices) is too risky.
Feel free to comment on this implementation
Thanks,
Boris
Changes since v1: - Everything :-)
[1]https://lists.freedesktop.org/archives/dri-devel/2017-November/157688.html [2]https://www.spinics.net/lists/dri-devel/msg174808.html
Boris Brezillon (6): drm/tegra: Fix a device_node leak when the DRM panel is not found drm/panel: Make of_drm_find_panel() return an ERR_PTR() instead of NULL drm/panel: Let of_drm_find_panel() return -ENODEV when the panel is disabled drm/of: Make drm_of_find_panel_or_bridge() fail when the device is disabled drm/vc4: Support the case where the DSI device is disabled drm/panel: rpi-touchscreen: Set status to "fail" when ->probe() fails
drivers/gpu/drm/bridge/cdns-dsi.c | 2 +- drivers/gpu/drm/bridge/lvds-encoder.c | 4 +-- drivers/gpu/drm/drm_of.c | 13 ++++++-- drivers/gpu/drm/drm_panel.c | 11 +++++-- drivers/gpu/drm/exynos/exynos_dp.c | 9 ++++-- drivers/gpu/drm/exynos/exynos_drm_dpi.c | 9 ++++-- drivers/gpu/drm/exynos/exynos_drm_dsi.c | 6 ++-- drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_rgb.c | 8 +++-- drivers/gpu/drm/msm/disp/mdp4/mdp4_lcdc_encoder.c | 4 +-- .../gpu/drm/msm/disp/mdp4/mdp4_lvds_connector.c | 10 +++++-- drivers/gpu/drm/msm/dsi/dsi_host.c | 2 +- .../gpu/drm/panel/panel-raspberrypi-touchscreen.c | 35 ++++++++++++++++++++++ drivers/gpu/drm/rcar-du/rcar_lvds.c | 9 ++++-- drivers/gpu/drm/rockchip/dw-mipi-dsi.c | 2 +- drivers/gpu/drm/sti/sti_dvo.c | 7 +++-- drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c | 4 +-- drivers/gpu/drm/tegra/dsi.c | 6 ++-- drivers/gpu/drm/tegra/output.c | 17 ++++++----- drivers/gpu/drm/vc4/vc4_dsi.c | 15 ++++++++-- include/drm/drm_panel.h | 2 +- 20 files changed, 131 insertions(+), 44 deletions(-)