appleir: Add Apple IR receiver driver

[guest-seuros]

Summary

HID driver for Apple IR receivers (USB HID, vendor 0x05ac).
Supports Apple Remote and generic IR remotes using NEC protocol.

Supported hardware:

• Apple IR Receiver (0x8240, 0x8241, 0x8242, 0x8243, 0x1440)

Apple Remote protocol (proprietary 5-byte HID reports):

• Key down/repeat/battery-low detection
• 17-key mapping with two-packet command support
• Synthesized key-up via 125ms callout timer

Generic IR remotes (NEC protocol):

• Format: [0x26][0x7f][0x80][code][~code]
• Checksum: code + ~code = 0xFF
• Default keymap with 8 common codes
• See: https://techdocs.altium.com/display/FPGA/NEC+Infrared+Transmission+Protocol

Output via evdev with standard KEY_* codes.
Raw HID access available at /dev/hidraw0 for custom remapping.

Based on protocol reverse-engineering by James McKenzie et al.
Reference: drivers/hid/hid-appleir.c (Linux)

Tested on Mac Mini 2011 (0x05ac:0x8242).

Test Plan

This driver works with both NEC protocol and apple remotes.

[guest-seuros]

Remove debug DPRINTFN calls and verbose NEC code comments

[guest-seuros]

This driver was supposed to be a port form Linux Apple IR driver.

However, during development I discovered that the remote available for testing was not a genuine Apple remote but a generic NEC-compatible device with a apple logo on it.

As a result, the implementation was extended to support both the Apple protocol and generic NEC protocol devices. FreeBSD now supports both. (i tested it the the genuine remote)

[obiwac]

haven't done a hugely in-depth review yet. Overall looks pretty good!

general question though: is this driver not applicable to other IR receivers? in which case maybe a different name would be better. I mean if other generic NEC remotes exist with a different format to the Apple one, presumably that would imply there are other IR receivers which pass on the same reports.

sys/dev/hid/appleir.c

6–8

you are duplicating this comment later on, so no need to have it here in the license header

139

please add space between ; and /*

157–166

I don't know if I love this way of doing things. Perhaps this function should simply return (data >> 1) & KEY_MASK and then you track if a second report is expected separately?

212

are you sure about this? do you have an example battery low report which contains valid/sensible subsequent remote_id and key_code values?