Hello Kerogit, I have rebased the AVR DA/DB software interrupt emulation patch series (`avrdx_swint`) onto latest master and submitted the Pull Request on your behalf: https://github.com/apache/nuttx/pull/21129
All commit authorship, DCO sign-offs, and checkpatch requirements have been verified. Best regards, Swatantra On Wed, 28 Oct 2026 at 05:11, <[email protected]> wrote: > Hello, > > I noticed that the previous phase got merged - thanks to everyone > involved. Step 3 is support for software interrupt emulation, branch > name is avrdx_swint. Documentation builds without conflicts and > checkpatch reports all checks pass for every changed source code file. > > ============================ > > AVR: software interrupt emulation > > ## Summary > > This patch adds emulated software interrupt functionality to AVR DA/DB > architecture. The chip itself does not have any software interrupt and > the suggested way to implement one is to manipulate an I/O pin > configured to trigger a hardware interrupt. The implementation can serve > multiple users at the same time and also supports sharing the hardware > interrupt of the I/O port with other users. > > There is no in-tree user of this functionality yet, intended use is a > follow-up patch series that adds driver for WS2812 programmable LED. > > ## Impact > > **New feature**: software interrupt emulation for AVR DA/DB family > > **Impact on user**: none, new code is not enabled by default. Other AVR > families are not supported and not affected. > > **Impact on build**: new Kconfig options related to the new feature, > none otherwise > > **Impact on documentation**: zero latency interrupts guide updated > (mentions software interrupt emulation as a way to "get back into the > game") > > No impact on hardware, security or compatibility > > ## Testing > > I confirm that changes are verified on local setup and works as > intended: > * Build Host(s): Linux, AMD, GCC avr-gcc 14.2 > * Target(s): AVR DA/DB, tested on breadxavr > > Tested with the (not yet merged) WS2812 driver which uses this > functionality to notify the OS that the data transmission performed by > the zero latency interrupt handler is finished. > > Other than that - Documentation tested by make html, changed source code > files tested with checkpatch.sh > > ## PR verification Self-Check > > * [x] This PR introduces only one functional change. > * [x] I have updated all required description fields above. > * [x] My PR adheres to Contributing > [Guidelines](https://github.com/apache/nuttx/blob/master/CONTRIBUTING.md) > and > [Documentation]( > https://nuttx.apache.org/docs/latest/contributing/index.html) > (git commit title and message, coding standard, etc). > * [ ] My PR is still work in progress (not ready for review). > * [x] My PR is ready for review and can be safely merged into a > codebase. > > ============================ > > > On 2026-10-16 18:20, Swatantra wrote: > > Hi, No worries at all. Aspell definitely generates a lot of false > > positives > > with embedded hardware terminology, and Sphinx's autosectionlabel > > extension > > is notorious for flagging duplicate headings across sections. > > > > That's the beauty of pair-shepherding—catching those CI quirks together > > makes the upstream submission smooth. > > > > The force-pushed commit is now building cleanly in GitHub Actions CI. I > > will keep an eye on the review progress with Alin and the maintainers > > and > > keep you posted here. > > > > Best regards, > > Swatantra Yadav > > > > On Fri, 16 Oct 2026 at 21:39, <[email protected]> wrote: > > > >> Hi, thanks for posting the patches and for the fixes. I am > >> spellchecking > >> the commits as well but there is lot of noise (aspell doesn't like the > >> word datasheet, let alone AVR) so it's unfortunately easy to miss > >> something. And sorry about the duplicate label, I tested that document > >> with make html and found and fixed 2 of those warnings but it did not > >> occur to me that this label needs to be fixed in earlier patch than > >> where I did it. > >> > >> On 2026-10-16 17:00, Swatantra wrote: > >> > Hi Kerogit, > >> > > >> > I have submitted your Phase 2 series (Zero Latency Interrupt Handlers) > >> > as a > >> > pull request on GitHub: > >> > > >> > PR: https://github.com/apache/nuttx/pull/20706 > >> > > >> > Details of the submission: > >> > - Rebased cleanly on top of the latest apache/nuttx master (which > >> > includes > >> > merged PR #20677). > >> > - Fixed a minor documentation typo ("overriden" -> "overridden") in > >> > zerolatencyinterrupts.rst so that GitHub Actions CI checks (codespell) > >> > pass > >> > cleanly. > >> > - Preserved your original author attribution and DCO sign-off > >> > exclusively > >> > across all 4 commits. > >> > - Validated with checkpatch.sh and cvt2utf (0 errors, 0 warnings). > >> > > >> > > >> > Best regards, > >> > Swatantra Yadav > >> > > >> > On Fri, 16 Oct 2026 at 18:08, <[email protected]> wrote: > >> > > >> >> Hello, thanks, I see it merged, next step is zero latency interrupt > >> >> handling in branch named avrdx_zerolatency_intr. It rebased cleanly > on > >> >> current master branch. PR description is: > >> >> > >> >> ============================ > >> >> > >> >> AVR: support for zero latency interrupt handlers > >> >> > >> >> ## Summary > >> >> > >> >> This patch series provides support for so-called zero latency > >> >> interrupts > >> >> as described in > >> >> > >> >> > >> > https://nuttx.apache.org/docs/latest/guides/concurrency/zerolatencyinterrupts.html > >> >> . These can be used for driver code that needs the interrupt handler > >> >> to > >> >> run with as little overhead as possible (for example because it is > >> >> latency sensitive, runs very often etc.) This series does not add any > >> >> in-tree user, that is a topic of a planned follow-up (driver for > >> >> WS2812 > >> >> programmable LED.) > >> >> > >> >> This support is only added for DA/DB family of AVR chips. > >> >> > >> >> There are also some fixes of interrupt vectors table (incorrectly > >> >> numbered vectors as a result of duplicates) and Kconfig option > naming. > >> >> In addition to that, interupt vectors are renamed (for DA/DB family > >> >> only) to be able to override them with custom code written in C (and > >> >> compiled with GCC which expects __vector prefix in the name.) > >> >> > >> >> ## Impact > >> >> > >> >> New feature is added: zero latency interrupts that override regular > >> >> interrupt routine with a custom code completely independent on the > >> >> rest > >> >> of the operating system. > >> >> > >> >> There is no impact on existing users, all new code is off by default. > >> >> No > >> >> impact on other architectures nor other AVR families either. > >> >> > >> >> Impact on build - some Kconfig options are renamed from HAS_ to > >> >> preferred HAVE_ form. This renaming only touches existing Kconfig > >> >> options that are referred to by newly added Kconfig options (ie. the > >> >> new > >> >> option depends on the existing one.) All of the renamed options are > >> >> selected automatically based on chip in use so this change should > have > >> >> no impact on existing configurations. > >> >> > >> >> Impact on documentation - the guide linked in the summary is updated > >> >> to > >> >> describe specifics of the AVR implementation. > >> >> > >> >> No impact on hardware, security or compatibility. > >> >> > >> >> ## Testing > >> >> > >> >> I confirm that changes are verified on local setup and works as > >> >> intended: > >> >> * Build Host: Linux, AMD, GCC - avr-gcc 14.2 > >> >> * Target: AVR DA/DB, tested on breadxavr board > >> >> > >> >> To test that the interrupt vector renaming did not affect other AVR > >> >> families, mega1284p-xplained:nsh was built and disassembly compared. > >> >> There was no change. > >> >> > >> >> The feature was first tested by rudimentary application that > >> >> controlled > >> >> WS2812 programmable LED outside of the OS and then by a new driver > for > >> >> that LED using ws2812 example application from nuttx-apps. > >> >> > >> >> ## PR verification Self-Check > >> >> > >> >> * [x] This PR introduces only one functional change. > >> >> * [x] I have updated all required description fields above. > >> >> * [x] My PR adheres to Contributing > >> >> [Guidelines]( > >> https://github.com/apache/nuttx/blob/master/CONTRIBUTING.md) > >> >> and > >> >> [Documentation]( > >> >> https://nuttx.apache.org/docs/latest/contributing/index.html) > >> >> (git commit title and message, coding standard, etc). > >> >> * [ ] My PR is still work in progress (not ready for review). > >> >> * [x] My PR is ready for review and can be safely merged into a > >> >> codebase. > >> >> > >> >> ============================ > >> >> > >> >> On 2026-10-15 07:41, Swatantra wrote: > >> >> > Hi Kerogit, Alin, > >> >> > > >> >> > I have opened the Pull Request for Step 1 on GitHub on behalf of > >> >> > Kerogit: > >> >> > https://github.com/apache/nuttx/pull/20677 > >> >> > > >> >> > All 4 commits preserve Kerogit's original authorship and DCO > >> sign-offs, > >> >> > rebased cleanly onto current master, and checked with nxstyle. > >> >> > As discussed, we will proceed step-by-step: once this PR is > reviewed > >> >> > and > >> >> > merged, we can proceed with Step 2 (Zero Latency Interrupts). > >> >> > > >> >> > Best regards, > >> >> > Swatantra Yadav > >> >> > > >> >> > On Thu, 15 Oct 2026 at 03:15, <[email protected]> wrote: > >> >> > > >> >> >> Hello, > >> >> >> > >> >> >> thanks to everyone for the offers. First part of the series is > ready > >> >> >> in > >> >> >> the Git repository, branch is named avrdx_fixes_13.1. The PR > >> >> >> description > >> >> >> is below. I'll be looking at Github and if any question arise, I > will > >> >> >> answer them here. > >> >> >> > >> >> >> And just in case - since you mention splitting the patches into > >> >> >> individual PRs. If you mean breaking the branch into 4 separate > >> >> >> branches, I would advise against that. The features more or less > >> >> >> depend > >> >> >> on each other (software interrupt emulation changes file added by > the > >> >> >> zero latency interrupts, WS2812 uses both of these features etc.) > so > >> >> >> trying to split them up is most likely going to end with git > >> conflicts > >> >> >> and code that does not build. That's why I was planning to merge > this > >> >> >> in > >> >> >> step-by-step fashion. > >> >> >> > >> >> >> The filled PR template: > >> >> >> > >> >> >> ============================ > >> >> >> > >> >> >> AVR DA/DB: fix for build failure and other smaller fixes > >> >> >> > >> >> >> ## Summary > >> >> >> > >> >> >> This patch series fixes build failure for AVR DA/DB family and > adds > >> >> >> some > >> >> >> other smaller fixes. > >> >> >> > >> >> >> The build failure was caused by patch series that added > >> >> >> LIBC_ATOMIC_IRQ > >> >> >> Kconfig option during 13.1 development. Commit 4ca2256a9bee > selects > >> >> >> this > >> >> >> option by default for AVR chips but not for the DA/DB family, > causing > >> >> >> a > >> >> >> build failure (atomic functions are missing.) The first patch of > this > >> >> >> series simply adds missing "select LIBC_ATOMIC_IRQ" for this > family > >> as > >> >> >> well. > >> >> >> > >> >> >> Other than that, version 13.1 added a performance regression which > >> >> >> manifested as dropped bytes in USART peripheral during receive > (with > >> >> >> heavy round-robin preemptive scheduling load.) The regression was > >> >> >> bisected to commit b32712d0a2 that fixes some bugs (which were > >> >> >> affecting > >> >> >> AVR DA/DB default build as well) but apparently adds more > >> >> >> time-consuming > >> >> >> work to context switch with interrupts disabled. The patch for > this > >> >> >> simply documents this possibility in the USART driver description. > >> >> >> > >> >> >> The remaining patches fix unused variable warning, make (very > >> >> >> unlikely) > >> >> >> board initialization error more visible and reorder manipulation > with > >> >> >> stack pointer during context restore to do it in the way > (presumably) > >> >> >> intended by the chip manufacturer. > >> >> >> > >> >> >> ## Impact > >> >> >> > >> >> >> After the patch is applied, it is again possible to build the > code. > >> >> >> Other than that, there is no impact on existing code/users. > >> >> >> > >> >> >> The stack pointer reordering change is done in file shared with > other > >> >> >> AVR families - #ifdef blocks are used to cause no change for them > >> >> >> > >> >> >> ## Testing > >> >> >> > >> >> >> I confirm that changes are verified on local setup and work as > >> >> >> intended: > >> >> >> * Build Host: Linux, AMD, GCC-AVR 14.2 > >> >> >> * Target: AVR (AVR128DA28), breadxavr:nsh > >> >> >> > >> >> >> Testing logs before change: > >> >> >> > >> >> >> ``` > >> >> >> $ tools/configure.sh -l breadxavr:nsh > >> >> >> $ make -j16 > >> >> >> ... > >> >> >> avr-ld: .../nuttx.git/staging/libsched.a(sem_destroy.o): in > function > >> >> >> `.L3': > >> >> >> sem_destroy.c:(.text.nxsem_destroy+0x46): undefined reference to > >> >> >> `__atomic_load_4' > >> >> >> ... > >> >> >> ``` > >> >> >> > >> >> >> Testing logs after change: > >> >> >> > >> >> >> ``` > >> >> >> $ tools/configure.sh -l breadxavr:nsh > >> >> >> $ make -j16 > >> >> >> Register: nsh > >> >> >> Register: sh > >> >> >> LD: nuttx > >> >> >> Memory region Used Size Region Size %age Used > >> >> >> flash: 56377 B 128 KB 43.01% > >> >> >> sram: 780 B 16 KB 4.76% > >> >> >> eeprom: 0 B 512 B 0.00% > >> >> >> rodata: 606 B 4 KB 14.79% > >> >> >> CP: nuttx.hex > >> >> >> CP: nuttx.asm > >> >> >> ``` > >> >> >> > >> >> >> To verify that the stack pointer change did not affect other AVR > >> >> >> families, mega1284p-xplained:nsh was built before and after the > >> >> >> change. > >> >> >> The resulting binary was identical (with the exception of version > >> >> >> string.) > >> >> >> > >> >> >> Header and source files were checked by checkpatch with no issues > >> >> >> found, > >> >> >> spelling checked with aspell. > >> >> >> > >> >> >> ## PR verification Self-Check > >> >> >> > >> >> >> * [x] This PR introduces only one functional change. > >> >> >> * [x] I have updated all required description fields above. > >> >> >> * [x] My PR adheres to Contributing > >> >> >> [Guidelines]( > >> >> https://github.com/apache/nuttx/blob/master/CONTRIBUTING.md) > >> >> >> and > >> >> >> [Documentation]( > >> >> >> https://nuttx.apache.org/docs/latest/contributing/index.html) > >> >> >> (git commit title and message, coding standard, etc). > >> >> >> * [ ] My PR is still work in progress (not ready for review). > >> >> >> * [x] My PR is ready for review and can be safely merged into a > >> >> >> codebase. > >> >> >> > >> >> >> ============================ > >> >> >> > >> >> >> On 2026-10-14 18:20, Abhishek Mishra wrote: > >> >> >> > Hi, > >> >> >> > > >> >> >> > I'd be happy to help split the patches into individual PRs and > >> work on > >> >> >> > getting them merged. Please let me know how you'd like to > >> coordinate. > >> >> >> > > >> >> >> > Best regards, > >> >> >> > Abhishek > >> >> >> > > >> >> >> > On Wed, Oct 14, 2026 at 9:09 PM Alin Jerpelea < > [email protected]> > >> >> >> > wrote: > >> >> >> > > >> >> >> >> please prepare the first patches and I will handle them > >> >> >> >> > >> >> >> >> Best regards > >> >> >> >> Alin J > >> >> >> >> > >> >> >> >> On Wed, 14 Oct 2026, 16:37 Alin Jerpelea, <[email protected]> > >> >> wrote: > >> >> >> >> > >> >> >> >> > Hi, > >> >> >> >> > > >> >> >> >> > I can lend a hand tomorrow > >> >> >> >> > > >> >> >> >> > Thanks for your message > >> >> >> >> > > >> >> >> >> > Best regards > >> >> >> >> > Alin > >> >> >> >> > > >> >> >> >> > On Wed, 14 Oct 2026, 11:18 Felipe Moura Oliveira, < > >> >> >> [email protected]> > >> >> >> >> > wrote: > >> >> >> >> > > >> >> >> >> >> Hello, > >> >> >> >> >> > >> >> >> >> >> I am away from my desk for the next few days. If no one > offers > >> to > >> >> >> help > >> >> >> >> by > >> >> >> >> >> this weekend, I will reach out to you so I can help you with > >> this. > >> >> >> >> >> > >> >> >> >> >> Regards, > >> >> >> >> >> > >> >> >> >> >> > >> >> >> >> >> *--Felipe Moura de Oliveira* > >> >> >> >> >> Linkedin < > https://www.linkedin.com/in/felipe-oliveira-75a651a0 > >> > > >> >> >> >> >> > >> >> >> >> >> On Wed, 14 Oct 2026 at 10:48 <[email protected]> wrote: > >> >> >> >> >> > >> >> >> >> >> > Hello, > >> >> >> >> >> > > >> >> >> >> >> > I would like to ask someone to help me merge some patches > for > >> >> the > >> >> >> AVR > >> >> >> >> >> > architecture, DA/DB family. I have a series ready with > some > >> >> fixes > >> >> >> and > >> >> >> >> >> > some new features. Same as before, I don't have a Github > >> account > >> >> >> so I > >> >> >> >> am > >> >> >> >> >> > looking for someone who could open pull requests > >> >> >> >> >> > > >> >> >> >> >> > The series as a whole is available in my "nuttx.git" > >> repository > >> >> at > >> >> >> >> >> > git.kerogit.eu accessible through HTTP/S. The relevant > >> branch > >> >> is > >> >> >> >> named > >> >> >> >> >> > avrdx_ws2812_upstream . > >> >> >> >> >> > > >> >> >> >> >> > In its current form, the branch is not suitable for > merging > >> - it > >> >> >> would > >> >> >> >> >> > be more than one feature per one PR which is against the > >> >> >> contributing > >> >> >> >> >> > rules. My plan is, if someone decides to help, to split > the > >> >> series > >> >> >> >> into > >> >> >> >> >> > steps and merge these steps one by one. After one step is > >> >> merged, I > >> >> >> >> >> > would rebase the remainder on current master branch and > >> provide > >> >> >> next > >> >> >> >> >> > step. I also plan to prepare text to be filled in the PR > form > >> >> >> >> >> > (essentialy doing as much as possible to make the job > easier > >> for > >> >> >> the > >> >> >> >> >> > person who will interact with Github.) > >> >> >> >> >> > > >> >> >> >> >> > There are four features: > >> >> >> >> >> > > >> >> >> >> >> > 1. fixes - build failure introduced between 13.0 and 13.1, > >> >> >> documenting > >> >> >> >> >> > performance regression between these versions and some > minor > >> >> stuff > >> >> >> >> >> > 2. zero latency interrupt support - > >> >> >> >> >> > > >> >> >> >> >> > > >> >> >> >> >> > >> >> >> >> > >> >> >> > >> >> > >> > https://nuttx.apache.org/docs/latest/guides/concurrency/zerolatencyinterrupts.html > >> >> >> >> >> > 3. software interrupt emulation > >> >> >> >> >> > 4. lower half for WS2812 driver > >> >> >> >> >> > > >> >> >> >> >> > Thanks > >> >> >> >> >> > > >> >> >> >> >> > >> >> >> >> > > >> >> >> >> > >> >> >> > >> >> > >> >
