New mechanism

internal/temper/discovery_linux.go

@@ -0,0 +1,69 @@
+package temper
+
+import (
+	"context"
+	"os"
+	"path/filepath"
+	"strings"
+	"time"
+)
+
+// Function which scans /dev for temperXX devices (configured by udev)
+//
+// A timeout of 250ms is recommended but as YMMV, this function allows
+// for an arbitrary timeout.
+func FindTempersWithTimeout(timeout time.Duration) ([]*Temper, error) {
+	// list over dev folder for temperXX devices
+	dirEnts, err := os.ReadDir("/dev")
+	if err != nil {
+		return []*Temper{}, err
+	}
+
+	tempers := []*Temper{}
+	for _, d := range dirEnts {
+		if name := d.Name(); strings.HasPrefix(name, "temper") {
+			if isInputDevice(name) {
+				continue
+			}
+			temper, err := New(filepath.Join("/dev", name))
+			if err != nil {
+				continue
+			}
+			// attempt to take a reading from the temper
+			// if the reading times out, assume it's a false positive
+			ctx, cancel := context.WithTimeout(context.Background(), timeout)
+			_, err = temper.ReadCWithContext(ctx)
+			if err == nil {
+				tempers = append(tempers, temper)
+			} else {
+				// prevent file descriptor leaks
+				temper.Close()
+			}
+			cancel()
+		}
+	}
+	return tempers, nil
+}
+
+// Helper function to return list of temper devices available in /dev
+//
+// Uses the recommended default timeout of 250ms. See
+// FindTempersWithTimeout for more details
+func FindTempers() ([]*Temper, error) {
+	return FindTempersWithTimeout(time.Millisecond * 250)
+}
+
+// Determines if the current hidraw device also doubles as a virtual keyboard
+//
+// some temper devices also have a keyboard emulation mode.
+// The regular discovery function can trigger data entry mode, and cause
+// annoying and distracting typing to happen, so this function allows us to
+// skip the check on devices we know aren't temper sensors
+func isInputDevice(temperDescriptor string) bool {
+	hidrawDesc := strings.ReplaceAll(temperDescriptor, "temper", "hidraw")
+	inputPath := filepath.Join("/sys/class/hidraw", hidrawDesc, "device/input")
+	if _, statErr := os.Stat(inputPath); statErr == nil {
+		return true
+	}
+	return false
+}