shared/usb: correctly report the SD LUN as removable media#10967
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mikeysklar wants to merge 1 commit intoadafruit:mainfrom
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shared/usb: correctly report the SD LUN as removable media#10967mikeysklar wants to merge 1 commit intoadafruit:mainfrom
mikeysklar wants to merge 1 commit intoadafruit:mainfrom
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Respond with "unsupported" for the SD LUN (removable media) and OK for internal flash / SAVES LUNs (non-removable). Responding OK for a removable LUN tells macOS the medium is always present, and macOS then skips TEST_UNIT_READY polling. If the SD isn't ready at the single enumeration probe, macOS never re-checks and LUN 1 fails to publish an IOMedia node. Hathach documented this behavior back in adafruit#6555; the SD case wasn't differentiated at the time. Fixes adafruit#10965.
This was referenced Apr 22, 2026
mikeysklar
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What was wrong
The SD card exposed as a USB MSC LUN doesn't mount on macOS.
ioregshows the SCSI nub appears but never progresses to publishing anIOMedia. Linux handles the same firmware fine.Why: CircuitPython was telling the host "this LUN's medium is always present" for every LUN, including the SD card. On macOS that means "skip
TEST_UNIT_READYpolling" — so if the SD wasn't ready at the one-shot enumeration probe, macOS never re-checked and gave up on the LUN. Linux ignored the hint and kept polling, which is why it worked there.@hathach documented this exact macOS behavior back in #6555; the per-LUN distinction wasn't applied at the time.
What changed
Report the SD LUN as removable media, report internal flash and SAVES as non-removable. macOS now keeps polling TUR on the SD LUN and correctly picks up card insertion and removal.
~10 lines in
supervisor/shared/usb/usb_msc_flash.c— per-LUN branch on the existingPREVENT_ALLOW_MEDIUM_REMOVALhandler. No RAM or flash cost.Tested on
/dev/sdc+/dev/sddcorrect sizes, no regressionWindows not tested.
Related
Credit to @dhalbert for pointing at #6555 and @hathach for the original analysis.