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shared/usb: correctly report the SD LUN as removable media #10967

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shared/usb: correctly report the SD LUN as removable media #10967

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060019f
shared/usb: per-LUN response to PREVENT_ALLOW_MEDIUM_REMOVAL
mikeysklar Apr 22, 2026
a2b9e97
shared/usb: reply unsupported to PREVENT_ALLOW on all LUNs
mikeysklar Apr 23, 2026
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18 changes: 16 additions & 2 deletions supervisor/shared/usb/usb_msc_flash.c
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Original file line number Diff line number Diff line change
Expand Up @@ -214,8 +214,22 @@ int32_t tud_msc_scsi_cb(uint8_t lun, const uint8_t scsi_cmd[16], void *buffer, u

switch (scsi_cmd[0]) {
case SCSI_CMD_PREVENT_ALLOW_MEDIUM_REMOVAL:
// Host is about to read/write etc ... better not to disconnect disk
resplen = 0;
#ifdef SDCARD_LUN
if (lun == SDCARD_LUN) {
// Removable media (SD card). Respond "unsupported" so macOS
// keeps sending TEST_UNIT_READY periodically to detect card
// insertion/removal. Responding OK here causes macOS to skip
// TUR polling and miss media-present events on the SD LUN.
// See the discussion in adafruit/circuitpython#6555.
tud_msc_set_sense(lun, SCSI_SENSE_ILLEGAL_REQUEST, 0x20, 0x00);
resplen = -1;
} else
#endif
{
// Non-removable media (internal flash, SAVES). OK is fine;
// host assumes medium always present and skips TUR polling.
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resplen = 0;
}
break;

default:
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