[PATCH v4 0/2] spmi: core: Add generic DebugFS interface for bus inspection

[vamshi gajjela]

From: Vamshi Gajjela <vamshigajjela@xxxxxxxxxx>

This series introduces a generic, controller-agnostic DebugFS interface in the
SPMI core under /sys/kernel/debug/spmi/spmi-<nr>/ to inspect registered
controllers and perform SPMI transactions during board bringup and debugging.

Patch 1/2 renames drivers/spmi/spmi.c to spmi-core.c so that the core driver
and optional debugfs support can be linked into the spmi.ko composite module.

Patch 2/2 adds the DebugFS interface (name and xfer) along with its ABI
documentation under Documentation/ABI/testing/debugfs-spmi.

Changes in v4:
- Rebased onto spmi-next (8f70c729e68c).
- Split the rename of drivers/spmi/spmi.c -> spmi-core.c into a separate
  preparatory patch.
- Removed the 'detect' debugfs entry as MIPI SPMI does not mandate a universal
  register address across all slave devices, and probing 0x0000 fails on
  controllers with channel/register access policies such as Qualcomm PMIC Arb.
- Dropped redundant Runtime PM calls from spmi-debugfs.c since SPMI controller
  drivers manage their own runtime PM inside their transaction callbacks.
- Gated raw write ('w') and command ('c') operations behind
  #undef SPMI_ALLOW_WRITE_DEBUGFS (matching regmap-debugfs.c) so that the
  interface is read-only by default unless explicitly enabled in source.
- Updated Date and KernelVersion in Documentation/ABI/testing/debugfs-spmi.
- Link to v3: https://lore.kernel.org/r/20261019202107.888262-1-vamshigajjela@xxxxxxxxxx

Changes in v3:
- Move internal SPMI core command helpers (spmi_cmd(), spmi_read_cmd(),
  spmi_write_cmd()) and DebugFS prototypes out of the public
  include/linux/spmi.h header into a local drivers/spmi/spmi-internal.h
  header.

Changes in v2:
- Rename spmi.c to spmi-core.c and link spmi-debugfs.o into the composite
  spmi.o module so CONFIG_SPMI=m builds cleanly with CONFIG_DEBUG_FS=y.
- Route DebugFS bus operations through spmi_read_cmd(), spmi_write_cmd(),
  and spmi_cmd() instead of calling controller callbacks directly,
  preserving SPMI tracepoints and core validation.
- Allocate a per-open-file struct spmi_xfer_ctx in open() instead of
  sharing a controller-wide buffer, avoiding races across concurrent file
  descriptors, and store struct dentry *debugfs directly on
  struct spmi_controller.
- Reset *ppos = 0 on register read commands so repeated transactions on
  the same open file descriptor work without manual seeking.
- Restrict SPMI_CMD_ZERO_WRITE at address 0x00 to 7-bit payloads
  (data[0] <= 0x7f) per the MIPI SPMI specification, falling back to
  SPMI_CMD_WRITE for 8-bit values.
- Parse register addresses with kstrtou16() so values above 0xffff are
  rejected instead of silently truncated.
- Update Documentation/ABI/testing/debugfs-spmi to document per-fd xfer
  buffers and 7-bit Zero Write opcode selection.

Vamshi Gajjela (2):
  spmi: core: Rename spmi.c to spmi-core.c
  spmi: core: Add generic DebugFS interface for bus inspection

 Documentation/ABI/testing/debugfs-spmi |  68 +++++
 MAINTAINERS                            |   1 +
 drivers/spmi/Makefile                  |   2 +
 drivers/spmi/{spmi.c => spmi-core.c}   |  20 +-
 drivers/spmi/spmi-debugfs.c            | 341 +++++++++++++++++++++++++
 drivers/spmi/spmi-internal.h           |  28 ++
 include/linux/spmi.h                   |   6 +
 7 files changed, 460 insertions(+), 6 deletions(-)
 create mode 100644 Documentation/ABI/testing/debugfs-spmi
 rename drivers/spmi/{spmi.c => spmi-core.c} (97%)
 create mode 100644 drivers/spmi/spmi-debugfs.c
 create mode 100644 drivers/spmi/spmi-internal.h

-- 
2.56.0.317.g454f8302e1-goog