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![Ville Syrjälä](https://secure.gravatar.com/avatar/487f7745e50542e02ecbdc7c7bf70026.jpg?s=96&d=mm)
Ville Syrjälä committed 562836a269e
drm/dp_mst: Enable registration of AUX devices for MST ports All available downstream ports - physical and logical - are exposed for each MST device. They are listed in /dev/, following the same naming scheme as SST devices by appending an incremental ID. Although all downstream ports are exposed, only some will work as expected. Consider the following topology: +---------+ | ASIC | +---------+ Conn-0| | +----v----+ +----| MST HUB |----+ | +---------+ | | | |Port-1 Port-2| +-----v-----+ +-----v-----+ | MST | | SST | | Display | | Display | +-----------+ +-----------+ |Port-1 x MST Path | MST Device ----------+---------------------------------- sst:0 | MST Hub mst:0-1 | MST Display mst:0-1-1 | MST Display's disconnected DP out mst:0-1-8 | MST Display's internal sink mst:0-2 | SST Display On certain MST displays, the upstream physical port will ACK DPCD reads. However, reads on the local logical port to the internal sink will *NAK*. i.e. reading mst:0-1 ACKs, but mst:0-1-8 NAKs. There may also be duplicates. Some displays will return the same GUID when reading DPCD from both mst:0-1 and mst:0-1-8. There are some device-dependent behavior as well. The MST hub used during testing will actually *ACK* read requests on a disconnected physical port, whereas the MST displays will NAK. In light of these discrepancies, it's simpler to expose all downstream ports - both physical and logical - and let the user decide what to use. v3 changes: * Change WARN_ON_ONCE -> DRM_ERROR on dpcd read errors * Docstring and cosmetic fixes v2 changes: Moved remote aux device (un)registration to new mst connector late register and early unregister helpers. Drivers should call these from their own mst connector function hooks. This is to solve an issue during driver unload, where mst connector devices are unregistered before the remote aux devices are. In a setup where aux devices are created as children of connector devices, the aux device would be removed too early, and uncleanly. Doing so in early_unregister solves this issue, as that is called before connector unregistration. Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com> Signed-off-by: Leo Li <sunpeng.li@amd.com> Reviewed-by: Lyude Paul <lyude@redhat.com> Signed-off-by: Harry Wentland <harry.wentland@amd.com> Link: https://patchwork.freedesktop.org/patch/msgid/20190723232808.28128-3-sunpeng.li@amd.com