1 files changed, 400 insertions, 0 deletions
diff --git a/drivers/staging/gasket/gasket_sysfs.c b/drivers/staging/gasket/gasket_sysfs.c
new file mode 100644
index 000000000000..fc45f0d13e87
--- /dev/null
+++ b/drivers/staging/gasket/gasket_sysfs.c
@@ -0,0 +1,400 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (C) 2018 Google, Inc. */
+#include "gasket_sysfs.h"
+
+#include "gasket_core.h"
+
+#include <linux/device.h>
+#include <linux/printk.h>
+
+/*
+ * Pair of kernel device and user-specified pointer. Used in lookups in sysfs
+ * "show" functions to return user data.
+ */
+
+struct gasket_sysfs_mapping {
+	/*
+	 * The device bound to this mapping. If this is NULL, then this mapping
+	 * is free.
+	 */
+	struct device *device;
+
+	/* The Gasket descriptor for this device. */
+	struct gasket_dev *gasket_dev;
+
+	/* This device's set of sysfs attributes/nodes. */
+	struct gasket_sysfs_attribute *attributes;
+
+	/* The number of live elements in "attributes". */
+	int attribute_count;
+
+	/* Protects structure from simultaneous access. */
+	struct mutex mutex;
+
+	/* Tracks active users of this mapping. */
+	struct kref refcount;
+};
+
+/*
+ * Data needed to manage users of this sysfs utility.
+ * Currently has a fixed size; if space is a concern, this can be dynamically
+ * allocated.
+ */
+/*
+ * 'Global' (file-scoped) list of mappings between devices and gasket_data
+ * pointers. This removes the requirement to have a gasket_sysfs_data
+ * handle in all files.
+ */
+static struct gasket_sysfs_mapping dev_mappings[GASKET_SYSFS_NUM_MAPPINGS];
+
+/* Callback when a mapping's refcount goes to zero. */
+static void release_entry(struct kref *ref)
+{
+	/* All work is done after the return from kref_put. */
+}
+
+/* Look up mapping information for the given device. */
+static struct gasket_sysfs_mapping *get_mapping(struct device *device)
+{
+	int i;
+
+	for (i = 0; i < GASKET_SYSFS_NUM_MAPPINGS; i++) {
+		mutex_lock(&dev_mappings[i].mutex);
+		if (dev_mappings[i].device == device) {
+			kref_get(&dev_mappings[i].refcount);
+			mutex_unlock(&dev_mappings[i].mutex);
+			return &dev_mappings[i];
+		}
+		mutex_unlock(&dev_mappings[i].mutex);
+	}
+
+	dev_dbg(device, "%s: Mapping to device %s not found\n",
+		__func__, device->kobj.name);
+	return NULL;
+}
+
+/* Put a reference to a mapping. */
+static void put_mapping(struct gasket_sysfs_mapping *mapping)
+{
+	int i;
+	int num_files_to_remove = 0;
+	struct device_attribute *files_to_remove;
+	struct device *device;
+
+	if (!mapping) {
+		pr_debug("%s: Mapping should not be NULL\n", __func__);
+		return;
+	}
+
+	mutex_lock(&mapping->mutex);
+	if (kref_put(&mapping->refcount, release_entry)) {
+		dev_dbg(mapping->device, "Removing Gasket sysfs mapping\n");
+		/*
+		 * We can't remove the sysfs nodes in the kref callback, since
+		 * device_remove_file() blocks until the node is free.
+		 * Readers/writers of sysfs nodes, though, will be blocked on
+		 * the mapping mutex, resulting in deadlock. To fix this, the
+		 * sysfs nodes are removed outside the lock.
+		 */
+		device = mapping->device;
+		num_files_to_remove = mapping->attribute_count;
+		files_to_remove = kcalloc(num_files_to_remove,
+					  sizeof(*files_to_remove),
+					  GFP_KERNEL);
+		if (files_to_remove)
+			for (i = 0; i < num_files_to_remove; i++)
+				files_to_remove[i] =
+				    mapping->attributes[i].attr;
+		else
+			num_files_to_remove = 0;
+
+		kfree(mapping->attributes);
+		mapping->attributes = NULL;
+		mapping->attribute_count = 0;
+		put_device(mapping->device);
+		mapping->device = NULL;
+		mapping->gasket_dev = NULL;
+	}
+	mutex_unlock(&mapping->mutex);
+
+	if (num_files_to_remove != 0) {
+		for (i = 0; i < num_files_to_remove; ++i)
+			device_remove_file(device, &files_to_remove[i]);
+		kfree(files_to_remove);
+	}
+}
+
+/*
+ * Put a reference to a mapping N times.
+ *
+ * In higher-level resource acquire/release function pairs, the release function
+ * will need to release a mapping 2x - once for the refcount taken in the
+ * release function itself, and once for the count taken in the acquire call.
+ */
+static void put_mapping_n(struct gasket_sysfs_mapping *mapping, int times)
+{
+	int i;
+
+	for (i = 0; i < times; i++)
+		put_mapping(mapping);
+}
+
+void gasket_sysfs_init(void)
+{
+	int i;
+
+	for (i = 0; i < GASKET_SYSFS_NUM_MAPPINGS; i++) {
+		dev_mappings[i].device = NULL;
+		mutex_init(&dev_mappings[i].mutex);
+	}
+}
+
+int gasket_sysfs_create_mapping(struct device *device,
+				struct gasket_dev *gasket_dev)
+{
+	struct gasket_sysfs_mapping *mapping;
+	int map_idx = -1;
+
+	/*
+	 * We need a function-level mutex to protect against the same device
+	 * being added [multiple times] simultaneously.
+	 */
+	static DEFINE_MUTEX(function_mutex);
+
+	mutex_lock(&function_mutex);
+	dev_dbg(device, "Creating sysfs entries for device\n");
+
+	/* Check that the device we're adding hasn't already been added. */
+	mapping = get_mapping(device);
+	if (mapping) {
+		dev_err(device,
+			"Attempting to re-initialize sysfs mapping for device\n");
+		put_mapping(mapping);
+		mutex_unlock(&function_mutex);
+		return -EBUSY;
+	}
+
+	/* Find the first empty entry in the array. */
+	for (map_idx = 0; map_idx < GASKET_SYSFS_NUM_MAPPINGS; ++map_idx) {
+		mutex_lock(&dev_mappings[map_idx].mutex);
+		if (!dev_mappings[map_idx].device)
+			/* Break with the mutex held! */
+			break;
+		mutex_unlock(&dev_mappings[map_idx].mutex);
+	}
+
+	if (map_idx == GASKET_SYSFS_NUM_MAPPINGS) {
+		dev_err(device, "All mappings have been exhausted\n");
+		mutex_unlock(&function_mutex);
+		return -ENOMEM;
+	}
+
+	dev_dbg(device, "Creating sysfs mapping for device %s\n",
+		device->kobj.name);
+
+	mapping = &dev_mappings[map_idx];
+	mapping->attributes = kcalloc(GASKET_SYSFS_MAX_NODES,
+				      sizeof(*mapping->attributes),
+				      GFP_KERNEL);
+	if (!mapping->attributes) {
+		dev_dbg(device, "Unable to allocate sysfs attribute array\n");
+		mutex_unlock(&mapping->mutex);
+		mutex_unlock(&function_mutex);
+		return -ENOMEM;
+	}
+
+	kref_init(&mapping->refcount);
+	mapping->device = get_device(device);
+	mapping->gasket_dev = gasket_dev;
+	mapping->attribute_count = 0;
+	mutex_unlock(&mapping->mutex);
+	mutex_unlock(&function_mutex);
+
+	/* Don't decrement the refcount here! One open count keeps it alive! */
+	return 0;
+}
+
+int gasket_sysfs_create_entries(struct device *device,
+				const struct gasket_sysfs_attribute *attrs)
+{
+	int i;
+	int ret;
+	struct gasket_sysfs_mapping *mapping = get_mapping(device);
+
+	if (!mapping) {
+		dev_dbg(device,
+			"Creating entries for device without first "
+			"initializing mapping\n");
+		return -EINVAL;
+	}
+
+	mutex_lock(&mapping->mutex);
+	for (i = 0; strcmp(attrs[i].attr.attr.name, GASKET_ARRAY_END_MARKER);
+		i++) {
+		if (mapping->attribute_count == GASKET_SYSFS_MAX_NODES) {
+			dev_err(device,
+				"Maximum number of sysfs nodes reached for "
+				"device\n");
+			mutex_unlock(&mapping->mutex);
+			put_mapping(mapping);
+			return -ENOMEM;
+		}
+
+		ret = device_create_file(device, &attrs[i].attr);
+		if (ret) {
+			dev_dbg(device, "Unable to create device entries\n");
+			mutex_unlock(&mapping->mutex);
+			put_mapping(mapping);
+			return ret;
+		}
+
+		mapping->attributes[mapping->attribute_count] = attrs[i];
+		++mapping->attribute_count;
+	}
+
+	mutex_unlock(&mapping->mutex);
+	put_mapping(mapping);
+	return 0;
+}
+EXPORT_SYMBOL(gasket_sysfs_create_entries);
+
+void gasket_sysfs_remove_mapping(struct device *device)
+{
+	struct gasket_sysfs_mapping *mapping = get_mapping(device);
+
+	if (!mapping) {
+		dev_err(device,
+			"Attempted to remove non-existent sysfs mapping to "
+			"device\n");
+		return;
+	}
+
+	put_mapping_n(mapping, 2);
+}
+
+struct gasket_dev *gasket_sysfs_get_device_data(struct device *device)
+{
+	struct gasket_sysfs_mapping *mapping = get_mapping(device);
+
+	if (!mapping) {
+		dev_err(device, "device not registered\n");
+		return NULL;
+	}
+
+	return mapping->gasket_dev;
+}
+EXPORT_SYMBOL(gasket_sysfs_get_device_data);
+
+void gasket_sysfs_put_device_data(struct device *device, struct gasket_dev *dev)
+{
+	struct gasket_sysfs_mapping *mapping = get_mapping(device);
+
+	if (!mapping)
+		return;
+
+	/* See comment of put_mapping_n() for why the '2' is necessary. */
+	put_mapping_n(mapping, 2);
+}
+EXPORT_SYMBOL(gasket_sysfs_put_device_data);
+
+struct gasket_sysfs_attribute *
+gasket_sysfs_get_attr(struct device *device, struct device_attribute *attr)
+{
+	int i;
+	int num_attrs;
+	struct gasket_sysfs_mapping *mapping = get_mapping(device);
+	struct gasket_sysfs_attribute *attrs = NULL;
+
+	if (!mapping)
+		return NULL;
+
+	attrs = mapping->attributes;
+	num_attrs = mapping->attribute_count;
+	for (i = 0; i < num_attrs; ++i) {
+		if (!strcmp(attrs[i].attr.attr.name, attr->attr.name))
+			return &attrs[i];
+	}
+
+	dev_err(device, "Unable to find match for device_attribute %s\n",
+		attr->attr.name);
+	return NULL;
+}
+EXPORT_SYMBOL(gasket_sysfs_get_attr);
+
+void gasket_sysfs_put_attr(struct device *device,
+			   struct gasket_sysfs_attribute *attr)
+{
+	int i;
+	int num_attrs;
+	struct gasket_sysfs_mapping *mapping = get_mapping(device);
+	struct gasket_sysfs_attribute *attrs = NULL;
+
+	if (!mapping)
+		return;
+
+	attrs = mapping->attributes;
+	num_attrs = mapping->attribute_count;
+	for (i = 0; i < num_attrs; ++i) {
+		if (&attrs[i] == attr) {
+			put_mapping_n(mapping, 2);
+			return;
+		}
+	}
+
+	dev_err(device, "Unable to put unknown attribute: %s\n",
+		attr->attr.attr.name);
+}
+EXPORT_SYMBOL(gasket_sysfs_put_attr);
+
+ssize_t gasket_sysfs_register_store(struct device *device,
+				    struct device_attribute *attr,
+				    const char *buf, size_t count)
+{
+	ulong parsed_value = 0;
+	struct gasket_sysfs_mapping *mapping;
+	struct gasket_dev *gasket_dev;
+	struct gasket_sysfs_attribute *gasket_attr;
+
+	if (count < 3 || buf[0] != '0' || buf[1] != 'x') {
+		dev_err(device,
+			"sysfs register write format: \"0x<hex value>\"\n");
+		return -EINVAL;
+	}
+
+	if (kstrtoul(buf, 16, &parsed_value) != 0) {
+		dev_err(device,
+			"Unable to parse input as 64-bit hex value: %s\n", buf);
+		return -EINVAL;
+	}
+
+	mapping = get_mapping(device);
+	if (!mapping) {
+		dev_err(device, "Device driver may have been removed\n");
+		return 0;
+	}
+
+	gasket_dev = mapping->gasket_dev;
+	if (!gasket_dev) {
+		dev_err(device, "Device driver may have been removed\n");
+		return 0;
+	}
+
+	gasket_attr = gasket_sysfs_get_attr(device, attr);
+	if (!gasket_attr) {
+		put_mapping(mapping);
+		return count;
+	}
+
+	gasket_dev_write_64(gasket_dev, parsed_value,
+			    gasket_attr->data.bar_address.bar,
+			    gasket_attr->data.bar_address.offset);
+
+	if (gasket_attr->write_callback)
+		gasket_attr->write_callback(gasket_dev, gasket_attr,
+					    parsed_value);
+
+	gasket_sysfs_put_attr(device, gasket_attr);
+	put_mapping(mapping);
+	return count;
+}
+EXPORT_SYMBOL(gasket_sysfs_register_store);