DSI BRIDGE OPERATIONS(9)

💅 dsi bridge operations(9) 💅

okay so bestie, this is the Kernel API Manual page for dsi bridge operations, and it is lowkey giving “the rules of the DSI host bridge group chat.” 🫶 DSI host interfaces are expected to be implemented as bridges rather than encoders, but there are a few aspects of their operation that need to be defined so everyone gets a consistent interface. periodt. ✨

• A DSI host should keep the PHY powered down until the pre_enable operation is called. All lanes are in an undefined idle state up to this point, and it must not be assumed that it is LP-11. pre_enable should initialise the PHY, set the data lanes to LP-11, and set the clock lane to either LP-11 or HS depending on the mode_flag MIPI_DSI_CLOCK_NON_CONTINUOUS. 💖
• Ordinarily the downstream bridge DSI peripheral pre_enable will have been called before the DSI host. If the DSI peripheral requires LP-11 and/or the clock lane to be in HS mode prior to pre_enable, then it can set the pre_enable_prev_first flag to request the pre_enable (and post_disable) order to be altered to enable the DSI host first. 👑
• Either the CRTC being enabled, or the DSI host enable operation should switch the host to actively transmitting video on the data lanes. 🔥
• The reverse also applies. The DSI host disable operation or stopping the CRTC should stop transmitting video, and the data lanes should return to the LP-11 state. The DSI host post_disable operation should disable the PHY. If the pre_enable_prev_first flag is set, then the DSI peripheral's bridge post_disable will be called before the DSI host's post_disable. 🌸
• Whilst it is valid to call host_transfer prior to pre_enable or after post_disable, the exact state of the lanes is undefined at this point. The DSI host should initialise the interface, transmit the data, and then disable the interface again. 😭

🚨 real talk: those lane-state caveats are not a vibe to hand-wave. undefined is undefined, bestie.

• Ultra Low Power State (ULPS) is not explicitly supported by DRM. If implemented, it therefore needs to be handled entirely within the DSI Host driver. 💀

👀 SEE ALSO 👀

• Kernel file ./drivers/gpu/drm/drm_bridge.c overview(9)
• display driver integration(9)
• special care dsi(9)
• bridge chain format selection(9)
• drm_bridge_enter(9)
• drm_bridge_exit(9)
• drm_bridge_unplug(9)
• drm_bridge_get(9)
• drm_bridge_put(9)
• drm_bridge_clear_and_put(9)
• drm_bridge_put_void(9)
• drm_bridge_add(9)
• devm_drm_bridge_add(9)
• drm_bridge_remove(9)
• drm_bridge_attach(9)
• bridge operations(9)
• drm_bridge_chain_mode_valid(9)
• drm_bridge_chain_mode_set(9)
• drm_atomic_bridge_chain_disable(9)
• drm_atomic_bridge_chain_post_disable(9)
• drm_atomic_bridge_chain_pre_enable(9)
• drm_atomic_bridge_chain_enable(9)
• drm_atomic_bridge_chain_check(9)
• drm_bridge_detect(9)
• drm_bridge_get_modes(9)
• drm_bridge_edid_read(9)
• drm_bridge_hpd_enable(9)
• drm_bridge_hpd_disable(9)
• drm_bridge_hpd_notify(9)
• of_drm_find_and_get_bridge(9)
• of_drm_find_bridge(9)
• of_drm_get_bridge_by_endpoint(9)
• devm_drm_put_bridge(9)

🦋 cute little sign-off: this page’s source/version vibe is ./drivers/gpu/drm, and the date stamp is October 2026. mwah, go forth and bridge responsibly 💜🎀