Supporting DP/USB-C can result in a chain of several transparent bridges (PHY, redrivers, mux, etc). This results in drivers having similar boilerplate code for such bridges. Next, these drivers are susceptible to -EPROBE_DEFER loops: the next bridge can either be probed from the bridge->attach callback, when it is too late to return -EPROBE_DEFER, or from the probe() callback, when the next bridge might not yet be available, because it depends on the resources provided by the probing device. Last, but not least, this results in the the internal knowledge of DRM subsystem slowly diffusing into other subsystems, like PHY or USB/TYPEC. To solve all these issues, define a separate DRM helper, which creates separate aux device just for the bridge. During probe such aux device doesn't result in the EPROBE_DEFER loops. Instead it allows the device drivers to probe properly, according to the actual resource dependencies. The bridge auxdevs are then probed when the next bridge becomes available, sparing drivers from drm_bridge_attach() returning -EPROBE_DEFER. Proposed merge strategy: immutable branch with the drm commit, which is then merged into PHY and USB subsystems together with the corresponding patch. Dmitry Baryshkov (3): drm/display: add transparent bridge helper phy: qcom: qmp-combo: switch to DRM_SIMPLE_BRIDGE usb: typec: nb7vpq904m: switch to DRM_SIMPLE_BRIDGE drivers/gpu/drm/display/Kconfig | 9 ++ drivers/gpu/drm/display/Makefile | 2 + drivers/gpu/drm/display/drm_simple_bridge.c | 120 ++++++++++++++++++++ drivers/phy/qualcomm/Kconfig | 3 +- drivers/phy/qualcomm/phy-qcom-qmp-combo.c | 44 +------ drivers/usb/typec/mux/Kconfig | 3 +- drivers/usb/typec/mux/nb7vpq904m.c | 44 +------ include/drm/display/drm_simple_bridge.h | 19 ++++ 8 files changed, 156 insertions(+), 88 deletions(-) create mode 100644 drivers/gpu/drm/display/drm_simple_bridge.c create mode 100644 include/drm/display/drm_simple_bridge.h -- 2.39.2
