Boris Brezillon f32df58acc drm/bridge: Add the necessary bits to support bus format negotiation ... drm_bridge_state is extended to describe the input and output bus configurations. These bus configurations are exposed through the drm_bus_cfg struct which encodes the configuration of a physical bus between two components in an output pipeline, usually between two bridges, an encoder and a bridge, or a bridge and a connector. The bus configuration is stored in drm_bridge_state separately for the input and output buses, as seen from the point of view of each bridge. The bus configuration of a bridge output is usually identical to the configuration of the next bridge's input, but may differ if the signals are modified between the two bridges, for instance by an inverter on the board. The input and output configurations of a bridge may differ if the bridge modifies the signals internally, for instance by performing format conversion, or*modifying signals polarities. Bus format negotiation is automated by the core, drivers just have to implement the ->atomic_get_{output,input}_bus_fmts() hooks if they want to take part to this negotiation. Negotiation happens in reverse order, starting from the last element of the chain (the one directly connected to the display) up to the first element of the chain (the one connected to the encoder). During this negotiation all supported formats are tested until we find one that works, meaning that the formats array should be in decreasing preference order (assuming the driver has a preference order). Note that the bus format negotiation works even if some elements in the chain don't implement the ->atomic_get_{output,input}_bus_fmts() hooks. In that case, the core advertises only MEDIA_BUS_FMT_FIXED and lets the previous bridge element decide what to do (most of the time, bridge drivers will pick a default bus format or extract this piece of information from somewhere else, like a FW property). v10: * Add changelog to the commit message v9: * No changes v8: * Fix a test in drm_atomic_bridge_chain_select_bus_fmts() (Reported by Jonas) v7: * Adapt the code to deal with the fact that not all bridges in the chain have a bridge state v5 -> v6: * No changes v4: * Enhance the doc * Fix typos * Rename some parameters/fields * Reword the commit message v3: * Fix the commit message (Reported by Laurent) * Document the fact that bus formats should not be directly modified by drivers (Suggested by Laurent) * Document the fact that format order matters (Suggested by Laurent) * Propagate bus flags by default * Document the fact that drivers can tweak bus flags if needed * Let ->atomic_get_{output,input}_bus_fmts() allocate the bus format array (Suggested by Laurent) * Add a drm_atomic_helper_bridge_propagate_bus_fmt() * Mandate that bridge drivers return accurate input_fmts even if they are known to be the first element in the bridge chain v2: * Rework things to support more complex use cases Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com> Signed-off-by: Neil Armstrong <narmstrong@baylibre.com> [narmstrong: fixed doc in include/drm/drm_bridge.h:69 fmt->format] Reviewed-by: Jernej Skrabec <jernej.skrabec@siol.net> Tested-by: Jonas Karlman <jonas@kwiboo.se> Link: https://patchwork.freedesktop.org/patch/msgid/20200128135514.108171-7-boris.brezillon@collabora.com		2020-01-31 16:39:53 +01:00
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drm	drm/bridge: Add the necessary bits to support bus format negotiation	2020-01-31 16:39:53 +01:00
host1x	drm-misc-next for v5.6:	2019-12-17 13:57:54 +01:00
ipu-v3
vga	vga: Fix Kconfig indentation	2019-11-20 17:40:32 +01:00
Makefile