kernel: Add device layer

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

1 files changed, 143 insertions, 0 deletions

diff --git a/sys/kern/kern_device.c b/sys/kern/kern_device.c
new file mode 100644
index 0000000..9ea96fe
--- /dev/null
+++ b/sys/kern/kern_device.c
@@ -0,0 +1,143 @@
+/*
+ * Copyright (c) 2023-2024 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/device.h>
+#include <sys/types.h>
+#include <sys/errno.h>
+#include <vm/dynalloc.h>
+#include <string.h>
+
+#define MAX_MAJOR 256
+#define MAX_MINOR 256
+
+struct device_major {
+    void **devsw_tab;
+    uint16_t devsw_count;
+};
+
+static struct device_major devtab[MAX_MAJOR];
+
+/*
+ * Allocate a device major.
+ *
+ * Returns 0 on failure.
+ */
+devmajor_t
+dev_alloc_major(void)
+{
+    static devmajor_t next = 1;
+
+    if (next > MAX_MAJOR)
+        return 0;
+
+    return next++;
+}
+
+/*
+ * Allocates a device minor.
+ *
+ * @major: Major number for class of device.
+ *
+ * Returns 0 on failure.
+ */
+dev_t
+dev_alloc(devmajor_t major)
+{
+    struct device_major *devmajor;
+    size_t allocsize;
+
+    if (major >= MAX_MAJOR)
+        return 0;
+
+    devmajor = &devtab[major];
+    if (devmajor->devsw_count >= MAX_MINOR)
+        return 0;
+
+    /*
+     * Try to allocate a devsw table if needed.
+     *
+     * XXX: If MAX_MINOR is 256 then we'll need roughly 8 * 256
+     *      (2048) bytes to store each table. Perhaps we should
+     *      figure out a way we can save memory?
+     */
+    if (devmajor->devsw_tab == NULL) {
+        allocsize = sizeof(void *) * MAX_MINOR;
+        devmajor->devsw_tab = dynalloc(allocsize);
+
+        if (devmajor->devsw_tab == NULL)
+            return 0;
+
+        memset(devmajor->devsw_tab, 0, allocsize);
+    }
+
+    return ++devmajor->devsw_count;
+}
+
+/*
+ * Register a device.
+ *
+ * Returns less than zero value on failure.
+ */
+int
+dev_register(devmajor_t major, dev_t dev, void *devsw)
+{
+    struct device_major *devmajor;
+
+    if (major >= MAX_MAJOR)
+        return -EINVAL;
+
+    devmajor = &devtab[major];
+    if (dev > devmajor->devsw_count)
+        return -EINVAL;
+
+    devmajor->devsw_tab[dev] = devsw;
+    return 0;
+}
+
+/*
+ * Get a devsw structure from device major
+ * and minor numbers.
+ *
+ * @major: Major number to lookup.
+ * @dev: Minor number to lookup.
+ */
+void *
+dev_get(devmajor_t major, dev_t dev)
+{
+    struct device_major *devmajor;
+
+    if (major >= MAX_MAJOR)
+        return 0;
+
+    devmajor = &devtab[major];
+    if (dev > devmajor->devsw_count)
+        return NULL;
+
+    return devmajor->devsw_tab[dev];
+}