feat(MP/kernel): create sysfs to contains module attributs

- use callback to update sysfs with the core

src/06-mini-project/kernel/sysfs/sysfs.c

@@ -0,0 +1,141 @@
+// workspace/src/06-mini-project/kernel/sysfs/sysfs.c
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/device.h>
+#include <linux/sysfs.h>
+#include <linux/fs.h>
+#include <linux/err.h>
+
+#include "sysfs.h"
+
+static struct class *sysfs_class = NULL;
+static struct device *sysfs_device = NULL;
+
+/* Global static structure to hold the registered callbacks */
+static struct sysfs_callbacks device_cbs = {0};
+
+/* Callback triggered on sysfs temperature file read */
+static ssize_t temperature_show(struct device *dev, struct device_attribute *attr, char *buf) {
+    uint32_t temp = 0;
+
+    if (device_cbs.get_temperature) {
+        temp = device_cbs.get_temperature();
+    }
+
+    /* Format the temperature and write it to the buffer */
+    return snprintf(buf, PAGE_SIZE, "%u.%03u\n", temp / 1000, temp % 1000);
+}
+
+/* Callback triggered on sysfs mode file read */
+static ssize_t mode_show(struct device *dev, struct device_attribute *attr, char *buf) {
+    int mode = 0;
+
+    if (device_cbs.get_mode) {
+        mode = device_cbs.get_mode();
+    }
+
+    return snprintf(buf, PAGE_SIZE, "%d\n", mode);
+}
+
+/* Callback triggered on sysfs mode file write */
+static ssize_t mode_store(struct device *dev, struct device_attribute *attr, const char *buf, size_t count) {
+    int mode;
+
+    /* Safely convert string from user space to integer */
+    if (kstrtoint(buf, 10, &mode) == 0) {
+        if (device_cbs.set_mode) {
+            device_cbs.set_mode(mode);
+        }
+    }
+
+    return count;
+}
+
+/* Callback triggered on sysfs period_status file read */
+static ssize_t period_status_show(struct device *dev, struct device_attribute *attr, char *buf) {
+    uint32_t period = 0;
+
+    if (device_cbs.get_period) {
+        period = device_cbs.get_period();
+    }
+
+    return snprintf(buf, PAGE_SIZE, "%u\n", period);
+}
+
+/* Callback triggered on sysfs period_set file write */
+static ssize_t period_set_store(struct device *dev, struct device_attribute *attr, const char *buf, size_t count) {
+    uint32_t period;
+
+    if (kstrtouint(buf, 10, &period) == 0) {
+        if (device_cbs.set_period) {
+            device_cbs.set_period(period);
+        }
+    }
+
+    return count;
+}
+
+/* Create the sysfs attribute structures with proper permissions */
+static DEVICE_ATTR_RO(temperature);
+static DEVICE_ATTR_RW(mode);
+static DEVICE_ATTR_RO(period_status);
+static DEVICE_ATTR_WO(period_set);
+
+/* Group all attributes together to register them efficiently */
+static struct attribute *regulator_attrs[] = {
+    &dev_attr_temperature.attr,
+    &dev_attr_mode.attr,
+    &dev_attr_period_status.attr,
+    &dev_attr_period_set.attr,
+    NULL,
+};
+
+static const struct attribute_group regulator_group = {
+    .attrs = regulator_attrs,
+};
+
+int temp_regulator_sysfs_init(struct sysfs_callbacks *cbs) {
+    int ret;
+
+    /* Save the callbacks provided by the main module */
+    if (cbs) {
+        device_cbs = *cbs;
+    }
+
+    /* Create sysfs class */
+    sysfs_class = class_create(THIS_MODULE, "temp_regulator");
+    if (IS_ERR(sysfs_class)) {
+        return PTR_ERR(sysfs_class);
+    }
+
+    /* Create sysfs device */
+    sysfs_device = device_create(sysfs_class, NULL, MKDEV(0, 0), NULL, "regulator");
+    if (IS_ERR(sysfs_device)) {
+        class_destroy(sysfs_class);
+        return PTR_ERR(sysfs_device);
+    }
+
+    /* Register all files in the sysfs directory at once */
+    ret = sysfs_create_group(&sysfs_device->kobj, &regulator_group);
+    if (ret) {
+        device_destroy(sysfs_class, MKDEV(0, 0));
+        class_destroy(sysfs_class);
+        return ret;
+    }
+
+    return 0;
+}
+
+void temp_regulator_sysfs_exit(void) {
+    /* Clean up sysfs files and destroy resources */
+    if (sysfs_device != NULL) {
+        sysfs_remove_group(&sysfs_device->kobj, &regulator_group);
+        device_destroy(sysfs_class, MKDEV(0, 0));
+        sysfs_device = NULL;
+    }
+
+    if (sysfs_class != NULL) {
+        class_destroy(sysfs_class);
+        sysfs_class = NULL;
+    }
+}

src/06-mini-project/kernel/sysfs/sysfs.h

@@ -0,0 +1,24 @@
+// workspace/src/06-mini-project/kernel/sysfs/sysfs.h
+#ifndef SYSFS_H
+#define SYSFS_H
+
+#include <linux/types.h>
+
+/* Structure holding all the necessary callbacks to interact with the hardware */
+struct sysfs_callbacks {
+    uint32_t (*get_temperature)(void);
+
+    int (*get_mode)(void);
+    void (*set_mode)(int mode);
+
+    uint32_t (*get_period)(void);
+    void (*set_period)(uint32_t freq);
+};
+
+/* Register the callbacks and create the sysfs interface */
+int temp_regulator_sysfs_init(struct sysfs_callbacks *cbs);
+
+/* Remove sysfs files and destroy device and class */
+void temp_regulator_sysfs_exit(void);
+
+#endif /* SYSFS_H */