Koror ram capture support

[stefpopa]

PR Description

• Add debugfs interface for quick single-shot RX/ORx RAM captures
• Add full IIO device (adrv904x-ramc) with I/Q channel support and buffer infrastructure

PR Type

• Bug fix (a change that fixes an issue)
• New feature (a change that adds new functionality)
• Breaking change (a change that affects other repos or cause CIs to fail)

PR Checklist

• I have conducted a self-review of my own code changes
• I have compiled my changes, including the documentation
• I have tested the changes on the relevant hardware
• I have updated the documentation outside this repo accordingly
• I have provided links for the relevant upstream lore

[github-actions]

LLM review

This series adds a debugfs interface and a dedicated IIO device (adrv904x-ramc) for
triggering RX/ORx capture-RAM snapshots on the ADRV904X transceiver.

run: 29838719279

dff75231057fb - Add IIO device for RX/ORx RAM capture

Build failure: adrv904x_ramc_probe() calls devm_iio_kfifo_buffer_setup_ext(), but
ADRV904X in drivers/iio/trx-rf/Kconfig only selects CF_AXI_ADC (which pulls in
IIO_BUFFER/IIO_BUFFER_HW_CONSUMER/IIO_BUFFER_DMAENGINE, not IIO_KFIFO_BUF). Reproduced
with set_arch gcc_arm + auto_set_kconfig + make:

ld: vmlinux.o: in function `adrv904x_ramc_probe':
undefined reference to `devm_iio_kfifo_buffer_setup_ext'

Adding select IIO_KFIFO_BUF fixes the link, and a full ARCH=arm build then succeeds.

Data-correctness bug: adrv904x_ramc_capture_and_push() always splits the capture
buffer into two equal halves (offset = word_count / 2) to demux I/Q data. That matches the
RX/DPD capture RAM layout (adrv904x_datainterface.c: bankSize = wordCount >> 1, comment
"dpd capture memory 2 banks 8k each"), but the ORx capture RAM uses a different, fixed
layout (comment "ORx capture ram 3 banks 4k each": up to three fixed 4K-word banks depending
on the requested size). The halved split is bank-aligned for ORx only when
word_count == 8K; for every other ORx-valid sample_count (32-4096, or 12288) the demux
mixes data from the wrong physical banks and silently returns corrupted I/Q data on the
ORX0/ORX1 channels, without any error being reported to userspace.

CI warnings

The gcc_fanalyzer/clang_analyzer warnings for the dead-store struct device *dev in
adrv904x.c (lines ~1599-1948) all trace back to commit cb241a9d869ab, which predates this
review range, so they are pre-existing and not introduced by this series.

Verification

• Built with set_arch gcc_arm + auto_set_kconfig + make -j$(nproc) -C . O=build;
  reproduced the devm_iio_kfifo_buffer_setup_ext link error, then confirmed a
  select IIO_KFIFO_BUF fix produces a complete arch/arm/boot/zImage.
• Read adrv904x_datainterface.c's private adrv904x_RxOrxDataCaptureRead() to confirm the
  RX/DPD vs. ORx bank-layout difference (no ADRV904X hardware available to reproduce the
  ORx corruption at runtime).
• checkpatch.pl is clean on both commits, aside from the generic "does MAINTAINERS need
  updating?" notice, which is not actionable (this driver has no MAINTAINERS entry at all).
• Built the two touched files with W=1: no new warnings introduced by this series.

Suggested patches

Two --fixup=dff75231057fb commits, verified to git apply --check cleanly and to build
successfully for ARCH=arm:

1. select IIO_KFIFO_BUF in drivers/iio/trx-rf/Kconfig.
2. Restrict ORx sample_count to 8K (the only value for which the current 2-bank demux is
   correct) at sysfs-store time and defensively inside the capture path, instead of silently
   returning garbled data. Proper multi-bank ORx demux is left to the driver author to
   implement and validate against real hardware.

Apply the suggested patches with:

cd path/to/repository
export GITHUB_TOKEN=ghp_***
apply-patches --repo=analogdevicesinc/linux 29838719279

Install instructions

The following one-liner installs the script if not present already:

curl -fSsL "https://raw.githubusercontent.com/analogdevicesinc/doctools/refs/heads/main/ci/scripts/apply-patches.sh"      -o ~/.local/bin/apply-patches.sh &&   grep -q "/apply-patches.sh" ~/.bashrc || echo "source ~/.local/bin/apply-patches.sh" >> $_ ; . $_

More information at AI Usage.