eMMC device is just raw memory storage like an flash memory in an SD card. You need to format it, unless you are writing raw information. Once it is formatted, it can be accessed using an SD card interface. If you google, you will find some information on how to open an SD card and replace the existing memory device with your own eMMC device, but you will need excellent soldering skills as eMMC devices are packaged in BGA. Once you make it physically accessible, you can mount it to your system and read its content. If the eMMC chip is soldered in a board, you will need to unsolder it to read the content. eMMC protocol analyzers are very expensive (over US$ 5000).