The eMMC v4.4 specification defines a 512-byte Extended CSD register that contains eMMC parameters.
Digi has extended the
mmc command with the subcommand
ecsd to access the fields of this register.
=> help mmc mmc - MMC sub system Usage: ... (other subcommands omitted for clarity) mmc ecsd dump - dump ECSD values mmc ecsd read offset - read ECSD value at offset mmc ecsd write offset value - write ECSD value at offset