iodev: Add new framework for I/O and console devices

This replaces the earlier earlycon with a single shared console buffer
for all output devices.

Signed-off-by: Hector Martin <marcan@marcan.st>

Makefile

@@ -43,6 +43,7 @@ OBJECTS := \
 	exception.o exception_asm.o \
 	fb.o font.o font_retina.o \
 	heapblock.o \
+	iodev.o \
 	kboot.o \
 	main.o \
 	memory.o memory_asm.o \

src/fb.c

@@ -2,7 +2,9 @@
 
 #include "assert.h"
 #include "fb.h"
+#include "iodev.h"
 #include "string.h"
+#include "types.h"
 #include "utils.h"
 #include "xnuboot.h"
 
@@ -206,17 +208,23 @@ void fb_console_reserve_lines(u32 n)
         fb_console_scroll(1 + n - (console.cursor.max_row - console.cursor.row));
 }
 
-void fb_console_write(const char *bfr, size_t len)
+ssize_t fb_console_write(const char *bfr, size_t len)
 {
-    if (!is_primary_core())
-        return;
-    if (console.disabled)
-        return;
-    if (!console.initialized)
-        return;
+    ssize_t wrote = 0;
 
-    while (len--)
+    if (!is_primary_core())
+        return 0;
+    if (console.disabled)
+        return 0;
+    if (!console.initialized)
+        return 0;
+
+    while (len--) {
         fb_putchar(*bfr++);
+        wrote++;
+    }
+
+    return wrote;
 }
 
 void fb_console_enable(void)
@@ -228,3 +236,25 @@ void fb_console_disable(void)
 {
     console.disabled = 1;
 }
+
+static bool fb_console_iodev_can_write(void *opaque)
+{
+    UNUSED(opaque);
+    return console.initialized;
+}
+
+static ssize_t fb_console_iodev_write(void *opaque, const void *buf, size_t len)
+{
+    UNUSED(opaque);
+    return fb_console_write(buf, len);
+}
+
+const struct iodev_ops iodev_fb_ops = {
+    .can_write = fb_console_iodev_can_write,
+    .write = fb_console_iodev_write,
+};
+
+struct iodev iodev_fb = {
+    .ops = &iodev_fb_ops,
+    .usage = USAGE_CONSOLE,
+};

src/fb.h

@@ -29,7 +29,7 @@ void fb_display_logo(void);
 
 void fb_console_scroll(u32 n);
 void fb_console_reserve_lines(u32 n);
-void fb_console_write(const char *bfr, size_t len);
+ssize_t fb_console_write(const char *bfr, size_t len);
 
 void fb_console_enable(void);
 void fb_console_disable(void);

src/iodev.c

@@ -0,0 +1,143 @@
+/* SPDX-License-Identifier: MIT */
+
+//#define DEBUG_IODEV
+
+#include "iodev.h"
+#include "string.h"
+
+#ifdef DEBUG_IODEV
+#define dprintf printf
+#else
+#define dprintf(...)                                                                               \
+    do {                                                                                           \
+    } while (0)
+#endif
+
+#define CONSOLE_BUFFER_SIZE SZ_2K
+
+extern struct iodev iodev_uart;
+extern struct iodev iodev_fb;
+
+struct iodev *iodevs[IODEV_MAX] = {
+    &iodev_uart,
+    &iodev_fb,
+};
+
+char con_buf[CONSOLE_BUFFER_SIZE];
+size_t con_wp;
+size_t con_rp[IODEV_MAX];
+
+bool iodev_can_read(iodev_id_t id)
+{
+    if (!iodevs[id]->ops->can_read)
+        return false;
+
+    return iodevs[id]->ops->can_read(iodevs[id]->opaque);
+}
+
+bool iodev_can_write(iodev_id_t id)
+{
+    if (!iodevs[id]->ops->can_write)
+        return false;
+
+    return iodevs[id]->ops->can_write(iodevs[id]->opaque);
+}
+
+ssize_t iodev_read(iodev_id_t id, void *buf, size_t length)
+{
+    if (!iodevs[id]->ops->read)
+        return false;
+
+    return iodevs[id]->ops->read(iodevs[id]->opaque, buf, length);
+}
+
+ssize_t iodev_write(iodev_id_t id, const void *buf, size_t length)
+{
+    if (!iodevs[id]->ops->write)
+        return false;
+
+    return iodevs[id]->ops->write(iodevs[id]->opaque, buf, length);
+}
+
+#ifdef DEBUG_IODEV
+bool in_iodev = false;
+#endif
+
+void iodev_console_write(const void *buf, size_t length)
+{
+#ifdef DEBUG_IODEV
+    if (in_iodev) {
+        iodev_write(IODEV_UART, buf, length);
+        return;
+    }
+    in_iodev = true;
+#endif
+
+    dprintf("  iodev_console_write() wp=%d\n", con_wp);
+    for (iodev_id_t id = 0; id < IODEV_MAX; id++) {
+        if (!(iodevs[id]->usage & USAGE_CONSOLE)) {
+            /* Drop buffer */
+            con_rp[id] = con_wp + length;
+            continue;
+        }
+
+        if (!iodev_can_write(id))
+            continue;
+
+        if (con_wp > CONSOLE_BUFFER_SIZE)
+            con_rp[id] = max(con_wp - CONSOLE_BUFFER_SIZE, con_rp[id]);
+
+        dprintf("  rp=%d\n", con_rp[id]);
+        // Flush existing buffer to device if possible
+        while (con_rp[id] < con_wp) {
+            size_t buf_rp = con_rp[id] % CONSOLE_BUFFER_SIZE;
+            size_t block = min(con_wp - con_rp[id], CONSOLE_BUFFER_SIZE - buf_rp);
+
+            dprintf("  write buf %d\n", block);
+            ssize_t ret = iodev_write(id, &con_buf[buf_rp], block);
+
+            if (ret <= 0)
+                goto next_dev;
+
+            con_rp[id] += ret;
+        }
+
+        const u8 *p = buf;
+        size_t wrote = 0;
+
+        // Write the current buffer
+        while (wrote < length) {
+            ssize_t ret = iodev_write(id, p, length - wrote);
+
+            if (ret <= 0)
+                goto next_dev;
+
+            con_rp[id] += ret;
+            wrote += ret;
+            p += ret;
+        }
+
+    next_dev:;
+    }
+
+    // Update console buffer
+
+    if (length > CONSOLE_BUFFER_SIZE) {
+        buf += (length - CONSOLE_BUFFER_SIZE);
+        con_wp += (length - CONSOLE_BUFFER_SIZE);
+        length = CONSOLE_BUFFER_SIZE;
+    }
+
+    while (length) {
+        size_t buf_wp = con_wp % CONSOLE_BUFFER_SIZE;
+        size_t block = min(length, CONSOLE_BUFFER_SIZE - buf_wp);
+        memcpy(&con_buf[buf_wp], buf, block);
+        buf += block;
+        con_wp += block;
+        length -= block;
+    }
+
+#ifdef DEBUG_IODEV
+    in_iodev = false;
+#endif
+}

src/iodev.h

@@ -0,0 +1,39 @@
+/* SPDX-License-Identifier: MIT */
+
+#ifndef IODEV_H
+#define IODEV_H
+
+#include "types.h"
+#include "utils.h"
+
+typedef enum _iodev_id_t { IODEV_UART, IODEV_FB, IODEV_MAX } iodev_id_t;
+
+typedef enum _iodev_usage_t {
+    USAGE_CONSOLE = BIT(0),
+    USAGE_UARTPROXY = BIT(1),
+} iodev_usage_t;
+
+struct iodev_ops {
+    bool (*can_read)(void *opaque);
+    bool (*can_write)(void *opaque);
+    ssize_t (*read)(void *opaque, void *buf, size_t length);
+    ssize_t (*write)(void *opaque, const void *buf, size_t length);
+};
+
+struct iodev {
+    const struct iodev_ops *ops;
+
+    iodev_usage_t usage;
+    void *opaque;
+};
+
+extern struct iodev *iodevs[IODEV_MAX];
+
+bool iodev_can_read(iodev_id_t id);
+bool iodev_can_write(iodev_id_t id);
+ssize_t iodev_read(iodev_id_t id, void *buf, size_t length);
+ssize_t iodev_write(iodev_id_t id, const void *buf, size_t length);
+
+void iodev_console_write(const void *buf, size_t length);
+
+#endif

src/uart.c

@@ -2,8 +2,9 @@
 
 #include <stdarg.h>
 
-#include "types.h"
 #include "uart.h"
+#include "iodev.h"
+#include "types.h"
 #include "utils.h"
 #include "vsprintf.h"
 
@@ -96,3 +97,40 @@ void uart_flush(void)
     while (!(read32(UART_BASE + UTRSTAT) & 0x04))
         ;
 }
+
+static bool uart_iodev_can_write(void *opaque)
+{
+    UNUSED(opaque);
+    return true;
+}
+
+static bool uart_iodev_can_read(void *opaque)
+{
+    UNUSED(opaque);
+    return read32(UART_BASE + UTRSTAT) & 0x01;
+}
+
+static ssize_t uart_iodev_read(void *opaque, void *buf, size_t len)
+{
+    UNUSED(opaque);
+    return uart_read(buf, len);
+}
+
+static ssize_t uart_iodev_write(void *opaque, const void *buf, size_t len)
+{
+    UNUSED(opaque);
+    uart_write(buf, len);
+    return len;
+}
+
+static struct iodev_ops iodev_uart_ops = {
+    .can_read = uart_iodev_can_read,
+    .can_write = uart_iodev_can_write,
+    .read = uart_iodev_read,
+    .write = uart_iodev_write,
+};
+
+struct iodev iodev_uart = {
+    .ops = &iodev_uart_ops,
+    .usage = USAGE_CONSOLE | USAGE_UARTPROXY,
+};

src/utils.c

@@ -2,10 +2,9 @@
 
 #include <stdarg.h>
 
-#include "fb.h"
-#include "types.h"
-#include "uart.h"
 #include "utils.h"
+#include "iodev.h"
+#include "types.h"
 #include "vsprintf.h"
 
 static char ascii(char s)
@@ -75,8 +74,7 @@ int debug_printf(const char *fmt, ...)
     i = vsprintf(buffer, fmt, args);
     va_end(args);
 
-    uart_write(buffer, i);
-    fb_console_write(buffer, i);
+    iodev_console_write(buffer, i);
 
     return i;
 }