USB mmcblk support (realtek or others)

mmcsd cardusb

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.

Best Answer

Yes, this is how devices based on RTS5129 or RTS5139 work. I do have RTS5129 in my Vostro laptop as a cardreader, and it provides me with /dev/mmcblkc0 device.

Related Solutions

Support for usb 3.0

Do an lspci from a root prompt. Do you see anything about "USB 3.0" host adapter in that list? If so, you should enjoy the same support from USB 3.0 devices that Linux provides for USB 2.0 and USB 1.1, which ranges from "Works great!" to "I had to do a bunch of crazy stuff in udev to get this to do what I want" to "There's only Windows drivers for this!".

GRUB USB – GRUB and USB Serial Support

Didn't tried it myself, but I've found this information on the coreboot wiki (https://www.coreboot.org/GRUB2#On_a_USB_serial_or_USB_debug_adapter)

To enable serial, first find out the name of your usb serial port trough:

insmod nativedisk # needed not to get the disk disapearing when insmoding the *hci
insmod ehci
insmod ohci
insmod uhci
insmod usb
insmod usbserial_pl2303
insmod usbserial_ftdi
insmod usbserial_usbdebug
terminal_output

The terminal_output command should print it:

grub> terminal_output 
Active output terminals:
serial_usb1 gfxterm 
Available output terminals:
console vga_text serial 
Here we can see "serial_usb1" so we now know that its name is usb1

Then add the following on top of your grub.cfg:

insmod nativedisk
insmod ehci
insmod ohci
insmod uhci
insmod usb
insmod usbserial_pl2303
insmod usbserial_ftdi
insmod usbserial_usbdebug
serial --speed=115200 --word=8 --parity=no --stop=1 usb1
terminal_output --append serial_usb1
terminal_input --append serial_usb1

The following chips/protocols are supported:

usbdebug
ftdi
pl2303

The Wiki is outdated, but the answer seems legit.

Best Answer

Related Solutions

Support for usb 3.0

GRUB USB – GRUB and USB Serial Support

Related Question