pinephone-nuttx/display.zig

//***************************************************************************
//
// Licensed to the Apache Software Foundation (ASF) under one or more
// contributor license agreements.  See the NOTICE file distributed with
// this work for additional information regarding copyright ownership.  The
// ASF licenses this file to you under the Apache License, Version 2.0 (the
// "License"); you may not use this file except in compliance with the
// License.  You may obtain a copy of the License at
//
//   http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
// License for the specific language governing permissions and limitations
// under the License.
//
//***************************************************************************

//! PinePhone MIPI DSI Driver for Apache NuttX RTOS.
//! This MIPI DSI Interface is compatible with Zephyr MIPI DSI:
//! https://github.com/zephyrproject-rtos/zephyr/blob/main/include/zephyr/drivers/mipi_dsi.h

/// Import the Zig Standard Library
const std = @import("std");

/// Import the LoRaWAN Library from C
const c = @cImport({
    // NuttX Defines
    @cDefine("__NuttX__",  "");
    @cDefine("NDEBUG",     "");

    // NuttX Header Files
    @cInclude("arch/types.h");
    @cInclude("../../nuttx/include/limits.h");
    @cInclude("nuttx/config.h");
    @cInclude("inttypes.h");
    @cInclude("unistd.h");
    @cInclude("stdlib.h");
    @cInclude("stdio.h");
});

/// MIPI DSI Processor-to-Peripheral transaction types
const MIPI_DSI_GENERIC_LONG_WRITE = 0x29;

/// Write to MIPI DSI
pub export fn nuttx_mipi_dsi_dcs_write(
    dev: [*c]const mipi_dsi_device,  // MIPI DSI Host Device
    channel: u8,  // Virtual Channel ID
    cmd: u8,      // DCS Command
    buf: [*c]u8,  // Transmit Buffer
    len: usize    // Length of Buffer
) isize {  // On Success: Return number of written bytes. On Error: Return negative error code
    _ = dev; _ = buf;
    debug("mipi_dsi_dcs_write: channel={}, cmd={x}, len={}", .{ channel, cmd, len });
    std.debug.panic("nuttx_mipi_dsi_dcs_write not implemented", .{});
    return 0;
}

/// MIPI DSI Device
pub const mipi_dsi_device = extern struct {
    /// Number of Data Lanes
    data_lanes: u8,
    /// Display Timings
    timings: mipi_dsi_timings,
    /// Pixel Format
    pixfmt: u32,
    /// Mode Flags
    mode_flags: u32,
};

/// MIPI DSI Read / Write Message
pub const mipi_dsi_msg = extern struct {
    /// Payload Data Type
    type: u8,
    /// Flags controlling message transmission
    flags: u16,
    /// Command (only for DCS)
    cmd: u8,
    /// Transmit Buffer Length
    tx_len: usize,
    /// Transmit Buffer
    tx_buf: [*c]const u8,
    /// Receive Buffer Length
    rx_len: usize,
    /// Receive Buffer
    rx_buf: [*c]u8,
};

/// MIPI DSI Display Timings
pub const mipi_dsi_timings = extern struct {
    /// Horizontal active video
    hactive: u32,
    /// Horizontal front porch
    hfp: u32,
    /// Horizontal back porch
    hbp: u32,
    /// Horizontal sync length
    hsync: u32,
    /// Vertical active video
    vactive: u32,
    /// Vertical front porch
    vfp: u32,
    /// Vertical back porch
    vbp: u32,
    /// Vertical sync length
    vsync: u32,
};

pub export fn null_main(_argc: c_int, _argv: [*]const [*]const u8) c_int {
    _ = _argc;
    _ = _argv;
    test_zig();
    return 0;
}

pub export fn test_zig() void {
    _ = printf("HELLO ZIG ON PINEPHONE!\n");
    _ = nuttx_mipi_dsi_dcs_write(null, 0, MIPI_DSI_GENERIC_LONG_WRITE, null, 0);
}

///////////////////////////////////////////////////////////////////////////////
//  Panic Handler

/// Called by Zig when it hits a Panic. We print the Panic Message, Stack Trace and halt. See 
/// https://andrewkelley.me/post/zig-stack-traces-kernel-panic-bare-bones-os.html
/// https://github.com/ziglang/zig/blob/master/lib/std/builtin.zig#L763-L847
pub fn panic(
    message: []const u8, 
    _stack_trace: ?*std.builtin.StackTrace
) noreturn {
    // Print the Panic Message
    _ = _stack_trace;
    _ = puts("\n!ZIG PANIC!");
    _ = puts(@ptrCast([*c]const u8, message));

    // Print the Stack Trace
    _ = puts("Stack Trace:");
    var it = std.debug.StackIterator.init(@returnAddress(), null);
    while (it.next()) |return_address| {
        _ = printf("%p\n", return_address);
    }

    // Halt
    while(true) {}
}

///////////////////////////////////////////////////////////////////////////////
//  Logging

/// Called by Zig for `std.log.debug`, `std.log.info`, `std.log.err`, ...
/// https://gist.github.com/leecannon/d6f5d7e5af5881c466161270347ce84d
pub fn log(
    comptime _message_level: std.log.Level,
    comptime _scope: @Type(.EnumLiteral),
    comptime format: []const u8,
    args: anytype,
) void {
    _ = _message_level;
    _ = _scope;

    // Format the message
    var buf: [100]u8 = undefined;  // Limit to 100 chars
    var slice = std.fmt.bufPrint(&buf, format, args)
        catch { _ = puts("*** log error: buf too small"); return; };
    
    // Terminate the formatted message with a null
    var buf2: [buf.len + 1 : 0]u8 = undefined;
    std.mem.copy(
        u8, 
        buf2[0..slice.len], 
        slice[0..slice.len]
    );
    buf2[slice.len] = 0;

    // Print the formatted message
    _ = puts(&buf2);
}

///////////////////////////////////////////////////////////////////////////////
//  Imported Functions and Variables

/// For safety, we import these functions ourselves to enforce Null-Terminated Strings.
/// We changed `[*c]const u8` to `[*:0]const u8`
extern fn printf(format: [*:0]const u8, ...) c_int;
extern fn puts(str: [*:0]const u8) c_int;

/// LoRaWAN Event Queue
extern var event_queue: c.struct_ble_npl_eventq;

/// Aliases for Zig Standard Library
const assert = std.debug.assert;
const debug  = std.log.debug;