New Linux Patches For Supporting Lenovo ThinkPad X1 Carbon G14's Second Camera
The main RGB web camera of the ThinkPad X1 Carbon Gen 14 is already working under Linux but the laptop has a second MIPI IR camera designed for Windows Hello usage. Patches sent out on Thursday by Ruslan Koreev get that secondary camera working under Linux.
Koreev explained in the patch series enabling that second cam for the Lenovo ThinkPad X1 Carbon Gen 14 high-end laptop:
"The ThinkPad X1 Carbon Gen 14 (Panther Lake, Intel IPU7) has a second MIPI camera for Windows Hello: an ST VD55G1 monochrome global-shutter sensor, enumerated by ACPI as TBE20A1, with one CSI-2 lane, powered through an INT3472 discrete device that provides a power enable GPIO, a reset GPIO, a privacy LED and a 19.2 MHz clock. The RGB camera of the same laptop (Sony IMX471, TBE20A0) is already supported.
Patches 1 to 3 wire the sensor up on ACPI: the INT3472 supply mapping, the ipu-bridge entry and ACPI matching in the vd55g1 driver, which also has to defer its probe while the bridge has not attached the endpoint yet. Patch 4 adds monochrome pixel formats to the IPU7 ISYS, which only offered Bayer, YUV and RGB formats, so that a mono sensor can stream at all, and keeps the mono codes out of the Bayer order conversion in the CSI-2 cropping path, which warns about them otherwise.
Tested on that laptop with Fedora 44 (kernel 7.2.5 with these changes carried as out-of-tree modules): the sensor probes, libcamera negotiates Y8 and streams 804x704 at 58 fps, Y10 and Y10P stream with plain V4L2, and with the IR illuminator on the frames are good enough for face authentication with howdy."
The patches are out for review. If all goes well in the patch review process and quickly, it's possible the work may still land in time for the upcoming Linux v7.4 cycle.
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