Linux 5.15-rc2 is now available as the latest weekly release candidate for this next version of the Linux kernel. Linux 5.15 in turn should be out as stable around the start of November.

BayLibre developer Alexandre Bailon has posted a "request for comments" of a new open-source Direct Rendering Manager (DRM) driver for AI Processing Unit (APU) functionality. Initially the driver is catering to Mediatek SoCs with an AI co-processor but this DRM "APU" driver could be adapted to other hardware too.

With the Linux 5.15 merge window out of the way, the first drm-misc-next pull request has been sent in to DRM-Next for staging until the Linux 5.16 merge window opens up about two months from now.

The latest area where BPF is looking to expand within the Linux kernel is its CFS scheduler.

While Linux 5.15-rc1 was released on Sunday with its many changes, landing on Monday was a late change to raise the baseline GCC version requirement for building the Linux kernel.

On and off for years has been talk of an accelerator subsystem for the Linux kernel considering that for now most AI training/inference accelerator drivers end up lodged within the "char/misc" area of the kernel. That accelerator subsystem discussion has been restarted with talks of having such a subsystem or moving those drivers within the GPU/DRM subsystem space.

As expected this evening the Linux 5.15-rc1 kernel was released to top off the two week merge window that saw many changes to the kernel.

We are now down to the last day of the Linux 5.15 merge window and one of the patch series we have been waiting to see if it would land during this two week period was the "folios" code -- or that also was recently renamed to "pagesets" to address some concerns over the name.

In addition to the RISC-V changes merged last week for the Linux 5.15 kernel, a second batch of patches was merged this weekend.

While last week was the main "char/misc" pull request for the Linux 5.15 merge window, the Habana Labs driver changes were previously reverted from there due to opposition from the upstream kernel developers in the Direct Rendering Manager space. The concerning patches around DMA-BUF have now been removed and a new pull request submitted with updates to this AI driver for Linux 5.15.

Last week a number of patches were merged in the quest to provide the kernel with comprehensive compile-time and run-time detection of buffer overflows. Another patch series was sent out today while still for this cycle they are expected to enable the compiler warnings around array-bounds and zero-length-bounds.

One of the nice low-level improvements we've seen with Linux 5.15 is a number of pieces falling into place in the quest of upstreaming the real-time (RT) patches for Linux. The latest merge makes SLUB RT-compatible.

The DAMON kernel functionality developed by Amazon engineers has successfully landed in the Linux 5.15 tree.

In addition to Linus Torvalds dealing with the -Werror fallout, separately in kernel land there were also some significant performance regressions introduced during the Linux 5.15 that led to Linus reverting some of the changes.

Landing this past weekend was the surprise move by Linus Torvalds to enable "-Werror" behavior by default for all kernel builds. That compiler flag addition makes all warnings be treated as errors, which in turn stops the kernel build. As expected, this change has led to quite a mess.

While Linus Torvalds isn't much of a fan of FUSE / user-space file-systems, the FUSE code within the kernel does continue making improvements.

To help out memory pressure / out-of-memory killing solutions like systemd-oomd or Android's LMKD, Linux 5.15 is introducing the "process_mrelease" system call to more quickly free the memory of dying processes.

The platform-drivers-x86 area of the kernel continues to be quite active with particularly offering better support for modern Intel/AMD laptops. With Linux 5.15 there is another big batch of improvements that landed at the end of last week.

A change made by Linus Torvalds and merged today for Linux 5.15 is enabling the "-Werror" compiler flag by default for all kernel builds.

Very large IBM mainframes/servers were taking 30+ minutes to boot the Linux kernel... No, just not for POST'ing the system with memory training and the like, but for loading Linux. Fortunately, with the Linux 5.15 kernel there is a set of scalability enhancements to allow these large IBM systems to be able to boot in around five minutes.

Con Kolivas has worked on many patches for the Linux kernel over the past two decades and particularly focused on innovations around desktop performance/interactivity. For over a decade now he's primarily been focused on maintaining his work out-of-tree and not catering to mainline acceptance but now he is thinking of bowing out once more and ending his kernel development effort.

David Airlie submitted today the Direct Rendering Manager (DRM) graphics/display driver updates for the Linux 5.15 merge window.

The x86/IRQ changes for the Linux 5.15 kernel bring some unexpected improvements to old hardware.

It looks like the real-time (RT) patches for the Linux kernel are almost to the point of being fully upstream in the mainline Linux kernel. Merged for Linux 5.15 is the PREEMPT_RT locking code that represents a bulk of the outstanding RT patches.

Linux block subsystem maintainer and I/O expert Jens Axboe sent in his set of feature pull requests today for the Linux 5.15 kernel cycle.

Ingo Molnar began sending in his pull requests bright and early as usual for the just-opened Linux 5.15 merge window. With the scheduler changes for this next kernel version there are some improvements worth mentioning but also worth mentioning is what hasn't found its way to the kernel yet: any software optimizations around Intel Thread Director for upcoming Alder Lake processors.

As expected Linus Torvalds promoted Linux 5.14 to stable in providing the latest features, hardware support, and other improvements ahead of the autumn 2021 Linux distribution releases.

Near the beginning of the year was some rare work on Linux's floppy disk driver and -- a half-year later -- it was found out that not only do people with systems using floppy disks still move to newer kernels, but that work earlier in the year had regressed the Linux kernel's floppy disk handling. Now coming for Linux 5.15 is a fix.

If all goes according to plan the Linux 5.14 kernel will be released as stable today. Linux 5.14 has many new features but there is also a lot of work slated for the next cycle, Linux 5.15. Here's a look.

For nearly the past decade there has been calls for deprecating the Liux kernel's frame-buffer "FBDEV" device code though the code remains within the kernel. While these days most display drivers are DRM-based even in the embedded world, a lot of FBDEV code still ends up in kernel builds even when just wanting to use DRM's FBDEV emulation layer. But a patch proposal out of Red Hat would further split-up the FBDEV core support to allow less of it to be built.