kernel: drivers: Add DRIVER_DEFER() macro

- Add DRIVER_DEFER() macro to schedule initialization
  for lower priority drivers

- Expose `proc0' to the rest of the kernel

Signed-off-by: Ian Moffett <ian@osmora.org>

5 files changed, 142 insertions, 4 deletions

diff --git a/sys/arch/aarch64/conf/link.ld b/sys/arch/aarch64/conf/link.ld
index c64cec3..2aa8c93 100644
--- a/sys/arch/aarch64/conf/link.ld
+++ b/sys/arch/aarch64/conf/link.ld
@@ -40,6 +40,12 @@ SECTIONS
         __drivers_init_end = .;
     } :rodata
 
+    .drivers.defer : {
+        __driversd_init_start = .;
+        *(.drivers.defer .drivers.defer)
+        __driversd_init_end = .;
+    } :rodata
+
     /* Move to the next memory page for .data */
     . += CONSTANT(MAXPAGESIZE);
 
diff --git a/sys/arch/amd64/conf/link.ld b/sys/arch/amd64/conf/link.ld
index 9c47a81..a43824f 100644
--- a/sys/arch/amd64/conf/link.ld
+++ b/sys/arch/amd64/conf/link.ld
@@ -29,6 +29,12 @@ SECTIONS
         __drivers_init_end = .;
     } :rodata
 
+    .drivers.defer : {
+        __driversd_init_start = .;
+        *(.drivers.defer .drivers.defer)
+        __driversd_init_end = .;
+    } :rodata
+
     . += CONSTANT(MAXPAGESIZE);
 
     .data : {
diff --git a/sys/include/sys/driver.h b/sys/include/sys/driver.h
index 05c40fa..6e4a267 100644
--- a/sys/include/sys/driver.h
+++ b/sys/include/sys/driver.h
@@ -31,27 +31,88 @@
 #define _SYS_DRIVER_H_
 
 #include <sys/cdefs.h>
+#include <sys/proc.h>
+#include <sys/types.h>
 
 #if defined(_KERNEL)
 
+/* Variable driver data */
+struct driver_var {
+    uint8_t deferred : 1;
+};
+
 struct driver {
     int(*init)(void);
+    struct driver_var *data;
 };
 
+extern struct proc g_proc0;
+
+/* Early (high priority) drivers */
 extern char __drivers_init_start[];
 extern char __drivers_init_end[];
 
+/* Deferred (low priority) drivers */
+extern char __driversd_init_start[];
+extern char __driversd_init_end[];
+
 #define DRIVER_EXPORT(INIT)                         \
+    static struct driver_var __driver_var = {       \
+        .deferred = 0                               \
+    };                                              \
+                                                    \
     __attribute__((used, section(".drivers")))      \
     static struct driver __driver_desc = {          \
         .init = INIT,                               \
+        .data = &__driver_var                       \
+    }
+
+/*
+ * Some drivers are not required to start up
+ * early for proper system operation and may
+ * be deferred to start at a later time.
+ *
+ * Examples of such (deferrable) drivers include code
+ * that waits for I/O (e.g., disks, network cards,
+ * et cetera). This allows for faster boot times
+ * as only *required* drivers are started before
+ * everything else.
+ *
+ * Drivers that wish to be deferred may export themselves
+ * via the DRIVER_DEFER() macro. The DRIVER_DEFERRED()
+ * macro gives the value of 1 if the current driver
+ * context has yet to be initialized. The driver may
+ * use this to defer requests for I/O.
+ */
+#if !defined(_INSTALL_MEDIA)
+#define DRIVER_DEFER(INIT)                           \
+    static struct driver_var __driver_var = {        \
+        .deferred = 1                                \
+    };                                               \
+                                                     \
+    __attribute__((used, section(".drivers.defer"))) \
+    static struct driver __driver_desc = {           \
+        .init = INIT,                                \
+        .data = &__driver_var                        \
     }
 
+#define DRIVER_DEFERRED() __driver_var.deferred
+#else
+#define DRIVER_DEFER(INIT) DRIVER_EXPORT(INIT)
+#define DRIVER_DEFERRED() 0
+#endif  /* _INSTALL_MEDIA */
+
 #define DRIVERS_INIT() \
     for (struct driver *__d = (struct driver *)__drivers_init_start;    \
          (uintptr_t)__d < (uintptr_t)__drivers_init_end; ++__d)         \
     {                                                                   \
         __d->init();                                                    \
     }
+
+#define DRIVERS_SCHED() \
+    spawn(&g_proc0,__driver_init_td, NULL, 0, NULL)
+
+void __driver_init_td(void);
+
 #endif  /* _KERNEL */
 #endif  /* !_SYS_DRIVER_H_ */
diff --git a/sys/kern/driver_subr.c b/sys/kern/driver_subr.c
new file mode 100644
index 0000000..29eac71
--- /dev/null
+++ b/sys/kern/driver_subr.c
@@ -0,0 +1,64 @@
+/*
+ * Copyright (c) 2023-2025 Ian Marco Moffett and the Osmora Team.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice,
+ *    this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of Hyra nor the names of its
+ *    contributors may be used to endorse or promote products derived from
+ *    this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <sys/driver.h>
+#include <sys/proc.h>
+#include <sys/cdefs.h>
+#include <sys/syslog.h>
+#include <sys/panic.h>
+#include <dev/timer.h>
+#include <machine/sync.h>
+
+/*
+ * Initialize early drivers
+ *
+ * XXX: This should *NOT* be called directly,
+ *      use DRIVERS_SCHED() instead.
+ */
+void
+__driver_init_td(void)
+{
+    const struct driver *dp;
+    struct driver_var *var;
+    struct proc *td;
+    uintptr_t start, end;
+
+    td = this_td();
+    start = (uintptr_t)__driversd_init_start;
+    end = (uintptr_t)__driversd_init_end;
+
+    for (dp = (void *)start; (uintptr_t)dp < end; ++dp) {
+        var = dp->data;
+        dp->init();
+        var->deferred = 0;
+    }
+
+    exit1(td, 0);
+    __builtin_unreachable();
+}
diff --git a/sys/kern/init_main.c b/sys/kern/init_main.c
index 665bade..ae3a666 100644
--- a/sys/kern/init_main.c
+++ b/sys/kern/init_main.c
@@ -44,7 +44,7 @@
 #include <vm/vm.h>
 #include <string.h>
 
-static struct proc proc0;
+struct proc g_proc0;
 
 static void
 copyright(void)
@@ -60,7 +60,7 @@ begin_install(void)
     struct cpu_info *ci;
 
     ci = this_cpu();
-    ci->curtd = &proc0;
+    ci->curtd = &g_proc0;
     hyra_install();
 }
 #endif
@@ -115,14 +115,15 @@ main(void)
     md_intoff();
     sched_init();
 
-    memset(&proc0, 0, sizeof(proc0));
+    memset(&g_proc0, 0, sizeof(g_proc0));
 
     /* Startup pid 1 */
-    spawn(&proc0, start_init, NULL, 0, NULL);
+    spawn(&g_proc0, start_init, NULL, 0, NULL);
     md_inton();
 
     /* Load all drivers */
     DRIVERS_INIT();
+    DRIVERS_SCHED();
 
 #if defined(_INSTALL_MEDIA)
     kprintf("Hyra install media detected\n");