Detect AMD GPU info via sysfs and block old cards

This wires up some new logic to start using sysfs to discover AMD GPU
information and detects old cards we can't yet support so we can fallback to CPU mode.

gpu/amd.go

@@ -0,0 +1,91 @@
+package gpu
+
+import (
+	"bufio"
+	"fmt"
+	"io"
+	"log/slog"
+	"os"
+	"path/filepath"
+	"strconv"
+	"strings"
+)
+
+// TODO - windows vs. non-windows vs darwin
+
+// Discovery logic for AMD/ROCm GPUs
+
+const (
+	DriverVersionFile     = "/sys/module/amdgpu/version"
+	GPUPropertiesFileGlob = "/sys/class/kfd/kfd/topology/nodes/*/properties"
+	// TODO probably break these down per GPU to make the logic simpler
+	GPUTotalMemoryFileGlob = "/sys/class/kfd/kfd/topology/nodes/*/mem_banks/*/properties" // size_in_bytes line
+	GPUUsedMemoryFileGlob  = "/sys/class/kfd/kfd/topology/nodes/*/mem_banks/*/used_memory"
+)
+
+func AMDDetected() bool {
+	_, err := AMDDriverVersion()
+	return err == nil
+}
+
+func AMDDriverVersion() (string, error) {
+	_, err := os.Stat(DriverVersionFile)
+	if err != nil {
+		return "", err
+	}
+	fp, err := os.Open(DriverVersionFile)
+	if err != nil {
+		return "", err
+	}
+	defer fp.Close()
+	verString, err := io.ReadAll(fp)
+	if err != nil {
+		return "", err
+	}
+	return strings.TrimSpace(string(verString)), nil
+}
+
+func AMDGFXVersions() []Version {
+	res := []Version{}
+	matches, _ := filepath.Glob(GPUPropertiesFileGlob)
+	for _, match := range matches {
+		fp, err := os.Open(match)
+		if err != nil {
+			slog.Debug(fmt.Sprintf("failed to open sysfs node file %s: %s", match, err))
+			continue
+		}
+		defer fp.Close()
+
+		scanner := bufio.NewScanner(fp)
+		// optionally, resize scanner's capacity for lines over 64K, see next example
+		for scanner.Scan() {
+			line := strings.TrimSpace(scanner.Text())
+			if strings.HasPrefix(line, "gfx_target_version") {
+				ver := strings.Fields(line)
+				if len(ver) != 2 || len(ver[1]) < 5 {
+					slog.Debug("malformed " + line)
+					continue
+				}
+				l := len(ver[1])
+				patch, err1 := strconv.ParseUint(ver[1][l-2:l], 10, 32)
+				minor, err2 := strconv.ParseUint(ver[1][l-4:l-2], 10, 32)
+				major, err3 := strconv.ParseUint(ver[1][:l-4], 10, 32)
+				if err1 != nil || err2 != nil || err3 != nil {
+					slog.Debug("malformed int " + line)
+					continue
+				}
+
+				res = append(res, Version{
+					Major: uint(major),
+					Minor: uint(minor),
+					Patch: uint(patch),
+				})
+			}
+		}
+	}
+	return res
+}
+
+func (v Version) ToGFXString() string {
+	return fmt.Sprintf("gfx%d%d%d", v.Major, v.Minor, v.Patch)
+}