SD Express Support Coming With The Linux 5.11 Kernel
Earlier this year work began on preparing SD Express card/host support for Linux and now with the Linux 5.11 kernel that will debut in early 2021 is this preliminary support.
SD Express promises faster transfer speeds thanks to support for PCI Express 4.0 and the NVMe 1.4 protocol. SD Express is to come to SDHC/SDXC/SDUC memory cards while retaining backwards compatibility with the legacy SD card interface. The Linux kernel needed to be adapted obviously and first initialize with the legacy SD interface and then checking host/card support for PCIe/NVMe support before making the connection upgrade.
News on SD Express has been rather dry since the SD Express 8.0 announcement back in May that promised up to 4x faster speeds. While there hasn't been any major SD Express announcements recently, the Linux kernel support is at least getting squared away. The Linux 5.11 kernel has the core support around SD Express for the SD 7.10 specification and newer.
Besides the core infrastructure support, Linux 5.11 also has support for SD Express within the rtsx_pci driver for the Realtek RTS5261 adapter. The RTS5261 was announced last year as one of the first SD Express Card readers based on the SD 7.0 specification.
This SD Express support was sent in this morning as part of the MMC/MEMSTICK changes for the now-open Linux 5.11 merge window.