Initial addition of bbswitch (WIP!)

Makefile

@@ -0,0 +1,15 @@
+obj-m := bbswitch.o
+
+KVERSION := $(shell uname -r)
+KDIR := /lib/modules/$(KVERSION)/build
+PWD := $(shell pwd)
+
+default:
+	$(MAKE) -C $(KDIR) M=$(PWD) modules
+
+clean:
+	$(MAKE) -C $(KDIR) M=$(PWD) clean
+
+load:
+	-/sbin/rmmod bbswitch
+	/sbin/insmod bbswitch.ko

bbswitch.c

@@ -0,0 +1,193 @@
+/**
+ * Disable discrete graphics (currently nvidia only)
+ *
+ * Based on:
+ * byo-switcheroo   Alex Williamson <alex.williamson@redhat.com>
+ * acpi_call        Michal Kottman
+ */
+#include <linux/pci.h>
+#include <linux/acpi.h>
+#include <linux/module.h>
+#include <asm/uaccess.h>
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("Toggle the discrete graphics card");
+
+extern struct proc_dir_entry *acpi_root_dir;
+
+static const char acpi_optimus_dsm_muid[] = {
+    0xF8, 0xD8, 0x86, 0xA4, 0xDA, 0x0B, 0x1B, 0x47,
+    0xA7, 0x2B, 0x60, 0x42, 0xA6, 0xB5, 0xBE, 0xE0,
+};
+
+static struct pci_dev *dis_dev;
+static acpi_handle dis_handle;
+static int dis_enabled = 0;
+
+/* shamelessly taken from nouveau_acpi.c */
+static int acpi_optimus_dsm(acpi_handle handle, int func, char *args,
+    uint32_t *result) {
+    struct acpi_buffer output = { ACPI_ALLOCATE_BUFFER, NULL };
+    struct acpi_object_list input;
+    union acpi_object params[4];
+    union acpi_object *obj;
+    int err;
+
+    input.count = 4;
+    input.pointer = params;
+    params[0].type = ACPI_TYPE_BUFFER;
+    params[0].buffer.length = sizeof(acpi_optimus_dsm_muid);
+    params[0].buffer.pointer = (char *)acpi_optimus_dsm_muid;
+    params[1].type = ACPI_TYPE_INTEGER;
+    params[1].integer.value = 0x00000100;
+    params[2].type = ACPI_TYPE_INTEGER;
+    params[2].integer.value = func;
+    params[3].type = ACPI_TYPE_BUFFER;
+    params[3].buffer.length = sizeof(args);
+    params[3].buffer.pointer = args;
+
+    err = acpi_evaluate_object(handle, "_DSM", &input, &output);
+    if (err) {
+        printk(KERN_WARNING "bbswitch: failed to evaluate _DSM: %s\n",
+            acpi_format_exception(err));
+        return err;
+    }
+
+    obj = (union acpi_object *)output.pointer;
+
+    if (obj->type == ACPI_TYPE_INTEGER)
+        // REVS (revision number) not found, possibly not an Optimus?
+        if (obj->integer.value == 0x80000002) {
+            printk(KERN_INFO "bbswitch: Optimus function not found\n");
+            return -ENODEV;
+        }
+
+    if (obj->type == ACPI_TYPE_BUFFER) {
+        if (obj->buffer.length == 4 && result) {
+            *result = 0;
+            *result |= obj->buffer.pointer[0];
+            *result |= (obj->buffer.pointer[1] << 8);
+            *result |= (obj->buffer.pointer[2] << 16);
+            *result |= (obj->buffer.pointer[3] << 24);
+        }
+    }
+
+    kfree(output.pointer);
+    return 0;
+}
+
+static void bbswitch_acpi_off(void) {
+    char args[] = {1, 0, 0, 3};
+    u32 result = 0;
+
+    if (!acpi_optimus_dsm(dis_handle, 0x1A, args, &result)) {
+        printk(KERN_INFO "bbswitch: Result of _DSM call: %08X\n", result);
+    }
+}
+static void bbswitch_acpi_on(void) {
+    
+}
+
+static void bbswitch_off(void) {
+    if (dis_enabled)
+        return;
+
+    printk(KERN_INFO "bbswitch: disabling discrete graphics\n");
+
+    pci_save_state(dis_dev);
+    pci_clear_master(dis_dev);
+    pci_disable_device(dis_dev);
+    pci_set_power_state(dis_dev, PCI_D3hot);
+
+    bbswitch_acpi_off();
+}
+
+static void bbswitch_on(void) {
+    if (!dis_enabled)
+        return;
+
+    printk(KERN_INFO "bbswitch: enabling discrete graphics\n");
+
+    bbswitch_acpi_on();
+
+    pci_set_power_state(dis_dev, PCI_D0);
+    pci_restore_state(dis_dev);
+    if (pci_enable_device(dis_dev))
+        printk(KERN_WARNING "bbswitch: failed to enable %s\n",
+            dev_name(&dis_dev->dev));
+    pci_set_master(dis_dev);
+}
+
+static int bbswitch_write(struct file *filp, const char __user *buff,
+    unsigned long len, void *data) {
+    char cmd[8];
+
+    if (len >= sizeof(cmd)) {
+        printk(KERN_ERR "bbswitch: Input too large (%lu)\n", len);
+        return -ENOSPC;
+    }
+
+    if (copy_from_user(cmd, buff, len))
+        return -EFAULT;
+
+    if (strncmp(cmd, "OFF", 3) == 0)
+        bbswitch_off();
+
+    if (strncmp(cmd, "ON", 2) == 0)
+        bbswitch_on();
+
+    return len;
+}
+
+static int bbswitch_read(char *page, char **start, off_t off,
+    int count, int *eof, void *data) {
+    int len = 0;
+    return len;
+}
+
+static int __init bbswitch_init(void) {
+    struct proc_dir_entry *acpi_entry;
+    struct pci_dev *pdev = NULL;
+    int class = PCI_CLASS_DISPLAY_VGA << 8;
+
+    while ((pdev = pci_get_class(class, pdev)) != NULL) {
+        struct acpi_buffer buf = { ACPI_ALLOCATE_BUFFER, NULL };
+        acpi_handle handle;
+
+        handle = DEVICE_ACPI_HANDLE(&pdev->dev);
+        if (!handle)
+            continue;
+
+        if (pdev->vendor != PCI_VENDOR_ID_INTEL) {
+            dis_dev = pdev;
+            dis_handle = handle;
+        }
+        acpi_get_name(handle, ACPI_FULL_PATHNAME, &buf);
+        printk(KERN_INFO "bbswitch: Found discrete VGA device %s: %s\n",
+            dev_name(&pdev->dev), (char *)buf.pointer);
+        kfree(buf.pointer);
+    }
+
+    if (dis_dev == NULL) {
+        printk(KERN_ERR "bbswitch: No discrete VGA device found\n");
+        return -ENODEV;
+    }
+
+    acpi_entry = create_proc_entry("bbswitch", 0660, acpi_root_dir);
+    if (acpi_entry == NULL) {
+        printk(KERN_ERR "bbswitch: Couldn't create proc entry\n");
+        return -ENOMEM;
+    }
+
+    acpi_entry->write_proc = bbswitch_write;
+    acpi_entry->read_proc = bbswitch_read;
+
+    return 0;
+}
+
+static void __exit bbswitch_exit(void) {
+    remove_proc_entry("bbswitch", acpi_root_dir);
+}
+
+module_init(bbswitch_init);
+module_exit(bbswitch_exit);