The Linux Kernel Begins Preparing Support For SD Express Cards
SD Express aims to deliver nearly four gigabytes per second for data transfers thanks to leveraging PCIe and NVMe. SD Express is coming to SDHC, SDXC, and SDUC memory cards. These new SD Express cards that are expected to begin hitting retail channels in the months ahead do offer backwards compatibility with the legacy SD interface. In fact, the devices are initialized at first through the legacy SD interface. Following the legacy initialization process, the MMC host and SD card are both checked for PCIe and NVMe support. If both sides support the upgrades, then the new interfaces are utilized.
The Linux kernel's MMC code has begun preparing this initial support for SD Express with that basic infrastructure handling. No new hardware support is introduced but just the fundamental checks for SD Express via PCI Express and SD Express 1.2V handling. Expect more to come on the SD Express for Linux support front in the weeks/months ahead.