[PATCH RFC v3 0/1] leds: asus-aura-scsi: Add ASUS Aura RGB LED driver for ROG NVMe enclosures

[Liang Haowen <nbg2974@gmail.com>]

Hello,

v3, addressing the five points of the second sashiko review round,
the ones Lee asked to review, explain or fix.

Changes since v2:

- Empty work runs no longer touch the device. schedule_work() while
  the zone work is executing re-queues it, and a colour cached in the
  meantime may already have been consumed; the re-queued run then had
  an empty dirty set but still issued MODE, APPLY and SAVE, and SAVE
  writes the enclosure flash. The work now snapshots the dirty mask
  first and returns before any SCSI command when nothing is pending.

- The dirty mask and the cached colours are now protected by a
  per-zone spinlock, and the work writes from a snapshot taken under
  that lock. Previously the colour write and the (unlocked) bit set
  could be reordered on weakly ordered architectures, letting the work
  consume the dirty bit with a stale colour and lose the update.

- LED class device names now include the sdev's H:C:T:L
  (asus-arion-<H:C:T:L>:ledN). Every enclosure gets its own SCSI
  host, so the names stay unique when more than one is connected.
  With the static names the LED core would register a second
  enclosure's LEDs under renamed nodes (asus-arion:led0_1), which is
  the wrong device identity. Like sd letters, the names are
  per-attachment.

The two low-severity items are false positives:

- blk_rq_map_kern() takes four arguments on current kernels
  (rq, buf, len, gfp); drivers/scsi/scsi_lib.c calls it exactly this
  way from scsi_execute_cmd().

- kzalloc_obj() exists in include/linux/slab.h since v7.0.

v3 was re-verified on hardware: per-LED colours, repeated identical
writes, concurrent updates from four writers and unplug under load
are clean.

Everything else is unchanged: the hardware description, the
scsi_device_handler that does not claim the sdev, the multicolor LED
interface, the protocol handling and the known caveats (manual attach
until a notifier lands; SAVE on every update writes the enclosure
flash, wear uncharacterized; NULL-parent LED registration to avoid
the sdev reference cycle).

One open question for the RFC stage: the driver is deliberately not
wired into Kconfig/Makefile/MAINTAINERS yet, because the agreed
direction with the SCSI side is a split into a SCSI transport helper
and a shared ASUS Aura LED interface, and the wiring would follow
that shape. Is deferring the wiring to that split acceptable for an
RFC, or would you rather have the driver buildable in-tree from this
series already?

Comments on the interface shape and on folding this into the shared
Aura work with Denis remain very welcome.

Signed-off-by: Liang Haowen <nbg2974@gmail.com>

Liang Haowen (1):
  leds: asus-aura-scsi: Add ASUS Aura RGB LED driver for ROG NVMe enclosures

 drivers/leds/leds-asus-aura-scsi.c | 375 +++++++++++++++++++++++++++++
 1 file changed, 375 insertions(+)

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2.55.0