logging: Use UART directly if available

Some SBIs don't implement the Debug Console extension. Using the UART is one solution, supporting the SBI Legacy extension might work too if it exists.

1 files changed, 46 insertions, 0 deletions

diff --git a/src/Console.zig b/src/Console.zig
new file mode 100644
index 0000000..a54bb41
--- /dev/null
+++ b/src/Console.zig
@@ -0,0 +1,46 @@
+// SPDX-FileCopyrightText: 2024 Himbeer <himbeer@disroot.org>
+//
+// SPDX-License-Identifier: AGPL-3.0-or-later
+
+const std = @import("std");
+
+const debug_console = @import("sbi/debug_console.zig");
+const fdt = @import("fdt.zig");
+const paging = @import("paging.zig");
+const uart = @import("uart.zig");
+
+provider: Provider,
+
+const Self = @This();
+
+pub const Provider = union(enum) {
+    uart_port: uart.Port.Writer,
+    sbi_debug: debug_console.Writer,
+};
+
+pub fn init(kmem: *paging.Table, dt: *const fdt.Tree, allocator: std.mem.Allocator) !void {
+    if (uart.default == null) {
+        try uart.init(kmem, dt, allocator);
+    }
+}
+
+pub fn autoChoose() ?Self {
+    if (uart.default) |uart_con| {
+        return .{
+            .provider = .{ .uart_port = uart_con.writer() },
+        };
+    } else if (debug_console.writer()) |sbi_con| {
+        return .{
+            .provider = .{ .sbi_debug = sbi_con },
+        };
+    } else |_| {}
+
+    return null;
+}
+
+pub fn writer(console: *const Self) std.io.AnyWriter {
+    switch (console.provider) {
+        .uart_port => return console.provider.uart_port.any(),
+        .sbi_debug => return console.provider.sbi_debug.any(),
+    }
+}