libplatsch: handle possible clones#9
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At the moment we miss the support to drive multiple connectors which are connected to the same CRTC, also called a hardware clone mode. libplatsch is not using the DRM atomic API due to it limited scope therefore using properties values isn't sufficient. Instead all possible connector ids need to be passed during the drmModeSetCrtc(). To find all connectors which belong to the same CRTC, the encoder behind each connector must be validated by making use of the encoders '.possible_clones' array. If a connector shall be added which belongs to an already used CRTC, a check is performed to see if this connector can be driven by the CRTC. In that case the connector id is added to the 'struct modeset_dev::conn_id' array and -EEXIST is returned. Because of this error, no new 'struct modeset_dev' is added and certain error() messages aren't printed because this can be a valid use-case. Signed-off-by: Marco Felsch <m.felsch@pengutronix.de>
lynxeye-dev
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Sep 10, 2025
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| for (i = 0; i < dev->max_conn_num; i++) { | ||
| if (dev->conn_id[i] == 0) | ||
| break; | ||
| } |
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Why is this iteration needed? AFAICS you already know the last used array entry by looking at dev->conn_num.
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| if (i == dev->max_conn_num) { | ||
| error("Failed to add connector-id: %u\n", connector_id); | ||
| return; | ||
| } |
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How would this happen? The array is sized to hold all connectors of the device, so this should not ever happen. Seems a bit over-defensive.
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| /* | ||
| * Get the global encoder idx first to be able to check for | ||
| * possible clonse later. |
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At the moment we miss the support to drive multiple connectors which are connected to the same CRTC, also called a hardware clone mode.
libplatsch is not using the DRM atomic API due to it limited scope therefore using properties values isn't sufficient. Instead all possible connector ids need to be passed during the drmModeSetCrtc().
To find all connectors which belong to the same CRTC, the encoder behind each connector must be validated by making use of the encoders '.possible_clones' array.
If a connector shall be added which belongs to an already used CRTC, a check is performed to see if this connector can be driven by the CRTC. In that case the connector id is added to the 'struct modeset_dev::conn_id' array and -EEXIST is returned.
Because of this error, no new 'struct modeset_dev' is added and certain error() messages aren't printed because this can be a valid use-case.