FreeBsd drivers

01_hello/Makefile

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+SRCS=hello.c
+KMOD=hello
+
+# Uncomment the following lines to cross compile to ARM64 architecture for the Raspberry Pi
+#CC=clang --target=aarch64-unknown-freebsd
+#MACHINE_ARCH=aarch64
+#MACHINE=arm64
+
+.include <bsd.kmod.mk>
+

01_hello/README.md

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+# 01_hello (FreeBSD version)
+
+A simple hello world style FreeBSD kernel module.
+
+This example can be compiled and run on a Raspberry Pi running FreeBSD or on an x86 computer.
+
+## Commands to manage the module
+
+Follow the kernel's log for new lines (recommended to do so in a separate terminal or tmux)
+```shell
+$ tail -F /var/log/messages
+```
+
+Loading the kernel module
+```shell
+# kldload ./hello.ko
+```
+
+Unloading the kernel module
+```shell
+# kldunload ./hello.ko
+```
+
+## Cross Compiling From x86 FreeBSD to AArch64 FreeBSD
+
+It is possible to cross compile the kernel module from an x86 version of FreeBSD to the Raspberry Pi version. Edit your Makefile as follows:
+
+```Make
+KMOD=hello
+SRCS=hello.c
+
+CC=clang --target=aarch64-unknown-freebsd
+
+CFLAGS+= -I/usr/src/sys/arm64/include
+
+MACHINE_ARCH=aarch64
+MACHINE=arm64
+
+.include <bsd.kmod.mk>
+```
+
+The file hello.ko can then be copied to the Raspberry Pi and loaded into the kernel with kldload command.

01_hello/hello.c

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+/*
+ *  Copyright [2025] John Holloway
+ *  Learning exercise. Use at your own risk
+ */
+
+#include <sys/types.h>
+#include <sys/errno.h>
+#include <sys/param.h>
+#include <sys/module.h>
+#include <sys/kernel.h>
+#include <sys/systm.h>
+
+static int loader(struct module *module, int what, void *arg) {
+    int error = 0;
+
+    switch (what) {
+        case MOD_LOAD:
+            printf("Module loaded into FreeBSD kernel\n");
+            break;
+        case MOD_UNLOAD:
+            printf("Module removed from the FreeBSD kernel\n");
+            break;
+        default:
+            error = EOPNOTSUPP;
+            break;
+    }
+    return (error);
+}
+
+static moduledata_t mod = {
+        "hello",
+        loader,
+        NULL
+};
+
+DECLARE_MODULE(hello, mod, SI_SUB_KLD, SI_ORDER_ANY
+);
+

02_better_hello/Makefile

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+SRCS=better_hello.c
+KMOD=better_hello
+
+# Uncomment the following lines to cross compile to ARM64 architecture for the Raspberry Pi
+#CC=clang --target=aarch64-unknown-freebsd
+#MACHINE_ARCH=aarch64
+#MACHINE=arm64
+
+.include <bsd.kmod.mk>
+

02_better_hello/README.md

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+# 02 better_hello (FreeBSD version)
+
+A simple hello world style FreeBSD kernel module.
+
+This example can be compiled and run on a Raspberry Pi running FreeBSD or on an x86 computer.
+
+## Commands to manage the module
+
+Follow the kernel's log for new lines (recommended to do so in a separate terminal or tmux)
+```shell
+$ tail -F /var/log/messages
+```
+
+Loading the kernel module
+```shell
+# kldload ./better_hello.ko
+```
+
+To get the metadata from the sysctrl use the following commands:
+
+```shell
+$ sysctl kern.better_hello
+kern.better_hello.version: 1.0
+kern.better_hello.license: BSD
+kern.better_hello.description: A simple Hello World kernel module
+kern.better_hello.author: John Holloway
+```
+
+To get more specific information, you can enter the child node in the sysctl command.
+```shell
+$ sysctl kern.better_hello.author
+kern.better_hello.author: John Holloway
+```
+
+Unloading the kernel module
+```shell
+# kldunload better_hello
+```
+
+## Cross Compiling From x86 FreeBSD to AArch64 FreeBSD
+
+It is possible to cross compile the kernel module from an x86 version of FreeBSD to the Raspberry Pi version. Edit your Makefile as follows:
+
+```Make
+KMOD=better_hello
+SRCS=better_hello.c
+
+CC=clang --target=aarch64-unknown-freebsd
+CFLAGS+= -I/usr/src/sys/arm64/include
+
+MACHINE_ARCH=aarch64
+MACHINE=arm64
+
+.include <bsd.kmod.mk>
+```
+
+The file hello.ko can then be copied to the Raspberry Pi and loaded into the kernel with kldload command.

02_better_hello/better_hello.c

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+/*
+ *  Copyright [2025] John Holloway
+ *  Learning exercise. Use at your own risk
+ */
+
+#include <sys/types.h>
+#include <sys/errno.h>
+#include <sys/param.h>
+#include <sys/module.h>
+#include <sys/kernel.h>
+#include <sys/systm.h>
+#include <sys/sysctl.h>  //  required for the metadata
+
+static struct sysctl_ctx_list sysctl_ctx;
+static struct sysctl_oid *sysctl_tree;
+
+static int load_metadata(void) {
+    // Add a sysctrl context and object identifier to the system control tree
+    if (sysctl_ctx_init(&sysctl_ctx)) {
+        return ENOMEM;
+    }
+
+    sysctl_tree = SYSCTL_ADD_NODE(&sysctl_ctx,
+                                  SYSCTL_STATIC_CHILDREN(_kern),
+                                  OID_AUTO,
+                                  "better_hello",
+                                  CTLFLAG_RW,
+                                  0,
+                                  "better_hello metadata");
+
+    // Add metadata entries
+    SYSCTL_ADD_STRING(&sysctl_ctx, SYSCTL_CHILDREN(sysctl_tree),
+                      OID_AUTO, "author", CTLFLAG_RD,
+                      "John Holloway", 0, "Module author");
+
+    SYSCTL_ADD_STRING(&sysctl_ctx, SYSCTL_CHILDREN(sysctl_tree),
+                      OID_AUTO, "description", CTLFLAG_RD,
+                      "A simple Hello World kernel module",
+                      0, "Module description");
+
+    SYSCTL_ADD_STRING(&sysctl_ctx, SYSCTL_CHILDREN(sysctl_tree),
+                      OID_AUTO, "license", CTLFLAG_RD,
+                      "GPL", 0, "Module license");
+
+    SYSCTL_ADD_STRING(&sysctl_ctx, SYSCTL_CHILDREN(sysctl_tree),
+                      OID_AUTO, "version", CTLFLAG_RD,
+                      "1.0", 0, "Module version");
+    return 0;
+}
+
+static int loader(struct module *module, int what, void *arg) {
+        int error = 0;
+
+        switch (what) {
+                case MOD_LOAD:
+                        printf("Module loaded into FreeBSD kernel\n"
+                               "Use sysctl to get the kernel metadata\n");
+                        error = load_metadata();
+                        break;
+
+                case MOD_UNLOAD:
+                        printf("Module removed from the FreeBSD kernel\n");
+
+                        // If we do not free the system call context
+                        // we end up with dangling pointers in the kernel
+                if (sysctl_ctx_free(&sysctl_ctx)) {
+                    printf("Can't free the system call context\n");
+                    error = ENOTEMPTY;
+                } else {
+                    printf("Metadata has been removed from sysctl tree\n");
+                }
+
+                        break;
+                default:
+                        error = EOPNOTSUPP;
+                        break;
+        }
+        return(error);
+}
+
+static moduledata_t mod = {
+        "better_hello",
+        loader,
+        NULL
+};
+
+DECLARE_MODULE(hello, mod, SI_SUB_KLD, SI_ORDER_ANY);
+

03_gpioctrl/Makefile

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+SRCS=gpioctrl.c 
+KMOD=gpioctrl
+
+CFLAGS+= -I/usr/obj/usr/src/arm64.aarch64/sys/GENERIC
+
+# Uncomment the following lines to cross compile to ARM64 architecture for the Raspberry Pi
+#CC=clang --target=aarch64-unknown-freebsd
+#MACHINE_ARCH=aarch64
+#MACHINE=arm64
+
+.include <bsd.kmod.mk>

03_gpioctrl/README.md

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+# 03_gpioctrl (FreeBSD version)
+
+A style FreeBSD kernel module that can both turn a GPIO pin ON and read from another pin. It will be using the [gpiobus -- GPIO bus system](https://man.freebsd.org/cgi/man.cgi?gpiobus(4)) kernel interface.
+
+This example can be compiled and run on a Raspberry Pi running FreeBSD or on an x86 computer.
+
+Unlike the 01_hello, this kernel module requires building the kernel headers and artifacts for FreeBSD. If you have not already done so, you can build them with the following commands:
+```shell
+# cd /usr/src
+# make -j$(sysctl -n hw.ncpu) buildkernel
+```
+
+## Hardware Setup
+![Raspberry Pi Wiring](led_button_Steckplatine.png)
+
+## Commands to manage the module
+
+Follow the kernel's log for new lines (recommended to do so in a separate terminal or tmux)
+```shell
+$ tail -F /var/log/messages
+```
+
+Loading the kernel module
+```shell
+# kldload ./gpioctrl.ko
+```
+
+Unloading the kernel module
+```shell
+# kldunload gpioctrl
+```
+
+## Finding the Correct GPIO Numbers
+Check your pins at [pinout.xyz](https://www.pinout.xyz)
+
+Using the `devinfo` command to find information regarding the gpio chips on the board:
+
+```shell
+$ devinfo -rv | grep gpio
+      gpio0 pnpinfo name=gpio@7e200000 compat=brcm,bcm2711-gpio 
+        gpiobus0
+        gpioc0
+        gpio1 pnpinfo name=gpio compat=raspberrypi,firmware-gpio 
+          gpiobus1
+          gpioc1
+      unknown pnpinfo name=gpiomem compat=brcm,bcm2835-gpiomem 
+    gpioled0 pnpinfo name=leds compat=gpio-leds 
+    gpioregulator0 pnpinfo name=sd_io_1v8_reg compat=regulator-gpio
+```
+
+We know that _bcm2711-gpio_ is the main GPIO controller on the Raspberry Pi, so we will use the GPIO with Offset 0.
+
+## Cross Compiling From x86 FreeBSD to AArch64 FreeBSD
+
+It is possible to cross compile the kernel module from an x86 version of FreeBSD to the Raspberry Pi version. Edit your Makefile as follows:
+
+```shell
+KMOD=gpioctrl
+
+SRCS=gpioctrl.c device_if.h bus_if.h
+
+CC=clang --target=aarch64-unknown-freebsd
+
+CFLAGS+= -I/usr/src/sys/arm64/include
+
+MACHINE_ARCH=aarch64
+
+MACHINE=arm64
+
+.include <bsd.kmod.mk>
+```
+
+The file gpio.ko can then be copied to the Raspberry Pi and loaded into the kernel with kldload command.