Linus Torvalds Rejects Faulty MMC Updates For Linux 7.0 Kernel

Linux kernel development operates on a rigorous testing framework where changes undergo extensive vetting in the linux-next integration tree before reaching Linus Torvalds. This process prevents unstable code from entering mainline kernels, a safeguard that proved crucial when Torvalds encountered the proposed MultiMediaCard (MMC) subsystem updates for the upcoming Linux 7.0 release cycle.

The rejected patchset included substantive hardware support improvements:

Feature	Device/Manufacturer	Benefit
Device IDs	NXP IW61x WiFi chips	SDIO-based WiFi hardware recognition
Secure Erase/TRIM	Kingston eMMC	Optimized flash storage maintenance
Controller Support	Mediatek MT8189	Enhanced compatibility for ARM-based systems
Core Updates	DW_MMC & SHDCI drivers	Code cleanups and maintenance improvements

Torvalds flagged critical build failures during merge review, specifically when the kernel was compiled with CONFIG_MULTIPLEXER=m (module configuration). The commit ad314348ceb4 ("mux: Add helper functions for getting optional and selected mux-state") created conflicting function definitions between mux/consumer.h and drivers/mux/core.c. This occurred because header guards checked for CONFIG_MULTIPLEXER while the module build defined CONFIG_MULTIPLEXER_MODULE, bypassing dummy function implementations and causing redefinition errors.

Torvalds' response was unequivocal: "No. Those changes are complete garbage and don't even compile. It has apparently never been in linux-next or been build-tested in any way... I will not be pulling anything more from you this merge window. Stop sending me untested crap."

Implications for Hardware Compatibility

This rejection delays several hardware-enabling features:

• NXP IW61x WiFi: Systems using these SDIO WiFi chips won't gain native support until Linux 7.1
• Kingston eMMC Optimization: Secure erase/TRIM operations remain unoptimized, potentially impacting write endurance and performance on embedded devices
• Mediatek MT8189: Chromebooks and tablets using this SoC miss storage controller refinements

Build Recommendations

For developers and homelab users requiring these features:

1. Wait for Linux 7.1: The changes may reappear in April 2026 after proper linux-next testing
2. Manual Backporting: Skilled users can cherry-pick commits from the MMC Git repository but must verify build integrity
3. Test Configurations: Always compile kernels with both =y (built-in) and =m (module) options for critical subsystems

The incident underscores the Linux kernel's uncompromising quality standards. As Torvalds noted, maintainers must ensure patches spend adequate time in linux-next—typically 1-2 weeks—to catch build failures and integration issues before mainline submission. For storage and embedded developers, this delay highlights the importance of validating driver changes against real hardware configurations early in the development cycle.