-> Nwkt 06.07.20 20:56:31: nasiel som na internetoch len toto:
Looking into the Linux kernel sources, you may find that there are rare cases when USB device provide mmcblk device. Realtek chips RTS5129, RTS5139, RTS5179 and RTS5170 provide MMC interface. I have found RTS5129 as integrated part of my laptop, and checked that it correctly handles vendor custom CMD56. Unfortunately, I don't know is it possible to buy external USB SD card reader based on mentioned chips.
Ale stale to vypada len na USB prevodnik, ovsem s plnou mmc funkcionalitou a nie len SD reader.