Can a USB card-reader ever appear as /dev/mmcblk0 and support the MMC ioctl commands?
I see there are some kernel driver modules such as:
rtsx_usb_sdmmc.ko (rtsx-usb-sdmmc)
rtsx_usb.ko (rtsx-usb)
Can these make a realtek card reader, attached to the USB bus appear as a real MMC device? I notice that all the USB card readers I have access to appear as /dev/sdX. which appear to be an emulated SCSI device. These emulated SCSI devices do not support all the MMC operations (ioctl).
Are there certain USB-attached card-readers (chips) that appear as a /dev/mmcblkX instead of /dev/sdX?
This would allow the card to support blkdiscard, trim or fstrim.
/dev/mmcblk0
,/dev/mmcblk1
... I think those readers are connected via PCI. Card readers connected via USB see the cards asdev/sda
,dev/sdb
... I have not seen a USB adapter, that makes linux see it as an MMC device, but maybe there are such adapters. However, the discard (trim) function can be built into the drive itself (I have such a USB pendrive). -- It can also help to 'wipe the whole device' (overwrite with zeros) to make a card or USB pendrive fast again, if it was originally fast, but is slow after a lot of writes,