1 files changed, 218 insertions, 0 deletions
diff --git a/drivers/lguest/lguest_bus.c b/drivers/lguest/lguest_bus.c
new file mode 100644
index 00000000000..9e7752cc800
--- /dev/null
+++ b/drivers/lguest/lguest_bus.c
@@ -0,0 +1,218 @@
+/*P:050 Lguest guests use a very simple bus for devices.  It's a simple array
+ * of device descriptors contained just above the top of normal memory.  The
+ * lguest bus is 80% tedious boilerplate code. :*/
+#include <linux/init.h>
+#include <linux/bootmem.h>
+#include <linux/lguest_bus.h>
+#include <asm/io.h>
+#include <asm/paravirt.h>
+
+static ssize_t type_show(struct device *_dev,
+                         struct device_attribute *attr, char *buf)
+{
+	struct lguest_device *dev = container_of(_dev,struct lguest_device,dev);
+	return sprintf(buf, "%hu", lguest_devices[dev->index].type);
+}
+static ssize_t features_show(struct device *_dev,
+                             struct device_attribute *attr, char *buf)
+{
+	struct lguest_device *dev = container_of(_dev,struct lguest_device,dev);
+	return sprintf(buf, "%hx", lguest_devices[dev->index].features);
+}
+static ssize_t pfn_show(struct device *_dev,
+			 struct device_attribute *attr, char *buf)
+{
+	struct lguest_device *dev = container_of(_dev,struct lguest_device,dev);
+	return sprintf(buf, "%u", lguest_devices[dev->index].pfn);
+}
+static ssize_t status_show(struct device *_dev,
+                           struct device_attribute *attr, char *buf)
+{
+	struct lguest_device *dev = container_of(_dev,struct lguest_device,dev);
+	return sprintf(buf, "%hx", lguest_devices[dev->index].status);
+}
+static ssize_t status_store(struct device *_dev, struct device_attribute *attr,
+                            const char *buf, size_t count)
+{
+	struct lguest_device *dev = container_of(_dev,struct lguest_device,dev);
+	if (sscanf(buf, "%hi", &lguest_devices[dev->index].status) != 1)
+		return -EINVAL;
+	return count;
+}
+static struct device_attribute lguest_dev_attrs[] = {
+	__ATTR_RO(type),
+	__ATTR_RO(features),
+	__ATTR_RO(pfn),
+	__ATTR(status, 0644, status_show, status_store),
+	__ATTR_NULL
+};
+
+/*D:130 The generic bus infrastructure requires a function which says whether a
+ * device matches a driver.  For us, it is simple: "struct lguest_driver"
+ * contains a "device_type" field which indicates what type of device it can
+ * handle, so we just cast the args and compare: */
+static int lguest_dev_match(struct device *_dev, struct device_driver *_drv)
+{
+	struct lguest_device *dev = container_of(_dev,struct lguest_device,dev);
+	struct lguest_driver *drv = container_of(_drv,struct lguest_driver,drv);
+
+	return (drv->device_type == lguest_devices[dev->index].type);
+}
+/*:*/
+
+struct lguest_bus {
+	struct bus_type bus;
+	struct device dev;
+};
+
+static struct lguest_bus lguest_bus = {
+	.bus = {
+		.name  = "lguest",
+		.match = lguest_dev_match,
+		.dev_attrs = lguest_dev_attrs,
+	},
+	.dev = {
+		.parent = NULL,
+		.bus_id = "lguest",
+	}
+};
+
+/*D:140 This is the callback which occurs once the bus infrastructure matches
+ * up a device and driver, ie. in response to add_lguest_device() calling
+ * device_register(), or register_lguest_driver() calling driver_register().
+ *
+ * At the moment it's always the latter: the devices are added first, since
+ * scan_devices() is called from a "core_initcall", and the drivers themselves
+ * called later as a normal "initcall".  But it would work the other way too.
+ *
+ * So now we have the happy couple, we add the status bit to indicate that we
+ * found a driver.  If the driver truly loves the device, it will return
+ * happiness from its probe function (ok, perhaps this wasn't my greatest
+ * analogy), and we set the final "driver ok" bit so the Host sees it's all
+ * green. */
+static int lguest_dev_probe(struct device *_dev)
+{
+	int ret;
+	struct lguest_device*dev = container_of(_dev,struct lguest_device,dev);
+	struct lguest_driver*drv = container_of(dev->dev.driver,
+						struct lguest_driver, drv);
+
+	lguest_devices[dev->index].status |= LGUEST_DEVICE_S_DRIVER;
+	ret = drv->probe(dev);
+	if (ret == 0)
+		lguest_devices[dev->index].status |= LGUEST_DEVICE_S_DRIVER_OK;
+	return ret;
+}
+
+/* The last part of the bus infrastructure is the function lguest drivers use
+ * to register themselves.  Firstly, we do nothing if there's no lguest bus
+ * (ie. this is not a Guest), otherwise we fill in the embedded generic "struct
+ * driver" fields and call the generic driver_register(). */
+int register_lguest_driver(struct lguest_driver *drv)
+{
+	if (!lguest_devices)
+		return 0;
+
+	drv->drv.bus = &lguest_bus.bus;
+	drv->drv.name = drv->name;
+	drv->drv.owner = drv->owner;
+	drv->drv.probe = lguest_dev_probe;
+
+	return driver_register(&drv->drv);
+}
+
+/* At the moment we build all the drivers into the kernel because they're so
+ * simple: 8144 bytes for all three of them as I type this.  And as the console
+ * really needs to be built in, it's actually only 3527 bytes for the network
+ * and block drivers.
+ *
+ * If they get complex it will make sense for them to be modularized, so we
+ * need to explicitly export the symbol.
+ *
+ * I don't think non-GPL modules make sense, so it's a GPL-only export.
+ */
+EXPORT_SYMBOL_GPL(register_lguest_driver);
+
+/*D:120 This is the core of the lguest bus: actually adding a new device.
+ * It's a separate function because it's neater that way, and because an
+ * earlier version of the code supported hotplug and unplug.  They were removed
+ * early on because they were never used.
+ *
+ * As Andrew Tridgell says, "Untested code is buggy code".
+ *
+ * It's worth reading this carefully: we start with an index into the array of
+ * "struct lguest_device_desc"s indicating the device which is new: */
+static void add_lguest_device(unsigned int index)
+{
+	struct lguest_device *new;
+
+	/* Each "struct lguest_device_desc" has a "status" field, which the
+	 * Guest updates as the device is probed.  In the worst case, the Host
+	 * can look at these bits to tell what part of device setup failed,
+	 * even if the console isn't available. */
+	lguest_devices[index].status |= LGUEST_DEVICE_S_ACKNOWLEDGE;
+	new = kmalloc(sizeof(struct lguest_device), GFP_KERNEL);
+	if (!new) {
+		printk(KERN_EMERG "Cannot allocate lguest device %u\n", index);
+		lguest_devices[index].status |= LGUEST_DEVICE_S_FAILED;
+		return;
+	}
+
+	/* The "struct lguest_device" setup is pretty straight-forward example
+	 * code. */
+	new->index = index;
+	new->private = NULL;
+	memset(&new->dev, 0, sizeof(new->dev));
+	new->dev.parent = &lguest_bus.dev;
+	new->dev.bus = &lguest_bus.bus;
+	sprintf(new->dev.bus_id, "%u", index);
+
+	/* device_register() causes the bus infrastructure to look for a
+	 * matching driver. */
+	if (device_register(&new->dev) != 0) {
+		printk(KERN_EMERG "Cannot register lguest device %u\n", index);
+		lguest_devices[index].status |= LGUEST_DEVICE_S_FAILED;
+		kfree(new);
+	}
+}
+
+/*D:110 scan_devices() simply iterates through the device array.  The type 0
+ * is reserved to mean "no device", and anything else means we have found a
+ * device: add it. */
+static void scan_devices(void)
+{
+	unsigned int i;
+
+	for (i = 0; i < LGUEST_MAX_DEVICES; i++)
+		if (lguest_devices[i].type)
+			add_lguest_device(i);
+}
+
+/*D:100 Fairly early in boot, lguest_bus_init() is called to set up the lguest
+ * bus.  We check that we are a Guest by checking paravirt_ops.name: there are
+ * other ways of checking, but this seems most obvious to me.
+ *
+ * So we can access the array of "struct lguest_device_desc"s easily, we map
+ * that memory and store the pointer in the global "lguest_devices".  Then we
+ * register the bus with the core.  Doing two registrations seems clunky to me,
+ * but it seems to be the correct sysfs incantation.
+ *
+ * Finally we call scan_devices() which adds all the devices found in the
+ * "struct lguest_device_desc" array. */
+static int __init lguest_bus_init(void)
+{
+	if (strcmp(paravirt_ops.name, "lguest") != 0)
+		return 0;
+
+	/* Devices are in a single page above top of "normal" mem */
+	lguest_devices = lguest_map(max_pfn<<PAGE_SHIFT, 1);
+
+	if (bus_register(&lguest_bus.bus) != 0
+	    || device_register(&lguest_bus.dev) != 0)
+		panic("lguest bus registration failed");
+
+	scan_devices();
+	return 0;
+}
+/* Do this after core stuff, before devices. */
+postcore_initcall(lguest_bus_init);