Another pass after comments review

- Using effect + old to manage updates instead of custom implementation
- Removed un-necessary functions
- Documentation tidy-up
- FFB_T500RS effects documentation rewritten, examples added
- Init sequence simplified (on-par with windows captures). It was initially put in place and kept because it was "working"
- Dropped the redundant second 0x02 and second 0x01 in constant upload path
- Constant upload, play, and update paths now sends signed level and direction instead of scaling the raw level
- changed T500RS_DBG to take the struct t500rs_device_entry * explicitly
- Updated makefile to support build without being git repo (DKMS, tarball, release package)

Author: cazzoo

Makefile

@@ -2,7 +2,20 @@ KDIR ?= /lib/modules/$(shell uname -r)/build
 
 # Auto-generated global build-time version for TMFF2
 TMFF2_BASE_VERSION ?= 0.1
-GIT_HASH := $(shell git rev-parse --short=7 HEAD 2>/dev/null || echo "local")
+
+# Allow packagers / CI to provide a fixed hash or full version:
+#   make GIT_HASH=deadbee
+#   make TMFF2_VERSION=0.1-1
+#
+# Only derive GIT_HASH from git if none was provided and this is a git checkout.
+ifeq ($(origin GIT_HASH), undefined)
+  GIT_HASH := $(shell if command -v git >/dev/null 2>&1 && [ -d .git ]; then \
+      git rev-parse --short=7 HEAD 2>/dev/null; \
+    else \
+      echo local; \
+    fi)
+endif
+
 BUILD_HASH := $(shell date +%s | sha1sum | cut -c1-7)
 
 TMFF2_VERSION ?= $(TMFF2_BASE_VERSION)-$(GIT_HASH)+b$(BUILD_HASH)

docs/FFBEFFECTS.md

@@ -1025,4 +1025,4 @@ binary    hex
     ff00.0021 = 0
     ff00.0021 = 0
     ff00.0021 = 0
-```
+```