1 // SPDX-License-Identifier: GPL-2.0
2 /* Copyright (C) 2018 Google, Inc. */
3 #include "gasket_sysfs.h"
5 #include "gasket_core.h"
7 #include <linux/device.h>
8 #include <linux/printk.h>
11 * Pair of kernel device and user-specified pointer. Used in lookups in sysfs
12 * "show" functions to return user data.
15 struct gasket_sysfs_mapping {
17 * The device bound to this mapping. If this is NULL, then this mapping
20 struct device *device;
22 /* The Gasket descriptor for this device. */
23 struct gasket_dev *gasket_dev;
25 /* This device's set of sysfs attributes/nodes. */
26 struct gasket_sysfs_attribute *attributes;
28 /* The number of live elements in "attributes". */
31 /* Protects structure from simultaneous access. */
34 /* Tracks active users of this mapping. */
39 * Data needed to manage users of this sysfs utility.
40 * Currently has a fixed size; if space is a concern, this can be dynamically
44 * 'Global' (file-scoped) list of mappings between devices and gasket_data
45 * pointers. This removes the requirement to have a gasket_sysfs_data
46 * handle in all files.
48 static struct gasket_sysfs_mapping dev_mappings[GASKET_SYSFS_NUM_MAPPINGS];
50 /* Callback when a mapping's refcount goes to zero. */
51 static void release_entry(struct kref *ref)
53 /* All work is done after the return from kref_put. */
56 /* Look up mapping information for the given device. */
57 static struct gasket_sysfs_mapping *get_mapping(struct device *device)
61 for (i = 0; i < GASKET_SYSFS_NUM_MAPPINGS; i++) {
62 mutex_lock(&dev_mappings[i].mutex);
63 if (dev_mappings[i].device == device) {
64 kref_get(&dev_mappings[i].refcount);
65 mutex_unlock(&dev_mappings[i].mutex);
66 return &dev_mappings[i];
68 mutex_unlock(&dev_mappings[i].mutex);
71 dev_dbg(device, "%s: Mapping to device %s not found\n",
72 __func__, device->kobj.name);
76 /* Put a reference to a mapping. */
77 static void put_mapping(struct gasket_sysfs_mapping *mapping)
80 int num_files_to_remove = 0;
81 struct device_attribute *files_to_remove;
82 struct device *device;
85 pr_debug("%s: Mapping should not be NULL\n", __func__);
89 mutex_lock(&mapping->mutex);
90 if (kref_put(&mapping->refcount, release_entry)) {
91 dev_dbg(mapping->device, "Removing Gasket sysfs mapping\n");
93 * We can't remove the sysfs nodes in the kref callback, since
94 * device_remove_file() blocks until the node is free.
95 * Readers/writers of sysfs nodes, though, will be blocked on
96 * the mapping mutex, resulting in deadlock. To fix this, the
97 * sysfs nodes are removed outside the lock.
99 device = mapping->device;
100 num_files_to_remove = mapping->attribute_count;
101 files_to_remove = kcalloc(num_files_to_remove,
102 sizeof(*files_to_remove),
105 for (i = 0; i < num_files_to_remove; i++)
107 mapping->attributes[i].attr;
109 num_files_to_remove = 0;
111 kfree(mapping->attributes);
112 mapping->attributes = NULL;
113 mapping->attribute_count = 0;
114 put_device(mapping->device);
115 mapping->device = NULL;
116 mapping->gasket_dev = NULL;
118 mutex_unlock(&mapping->mutex);
120 if (num_files_to_remove != 0) {
121 for (i = 0; i < num_files_to_remove; ++i)
122 device_remove_file(device, &files_to_remove[i]);
123 kfree(files_to_remove);
128 * Put a reference to a mapping N times.
130 * In higher-level resource acquire/release function pairs, the release function
131 * will need to release a mapping 2x - once for the refcount taken in the
132 * release function itself, and once for the count taken in the acquire call.
134 static void put_mapping_n(struct gasket_sysfs_mapping *mapping, int times)
138 for (i = 0; i < times; i++)
139 put_mapping(mapping);
142 void gasket_sysfs_init(void)
146 for (i = 0; i < GASKET_SYSFS_NUM_MAPPINGS; i++) {
147 dev_mappings[i].device = NULL;
148 mutex_init(&dev_mappings[i].mutex);
152 int gasket_sysfs_create_mapping(struct device *device,
153 struct gasket_dev *gasket_dev)
155 struct gasket_sysfs_mapping *mapping;
159 * We need a function-level mutex to protect against the same device
160 * being added [multiple times] simultaneously.
162 static DEFINE_MUTEX(function_mutex);
164 mutex_lock(&function_mutex);
165 dev_dbg(device, "Creating sysfs entries for device\n");
167 /* Check that the device we're adding hasn't already been added. */
168 mapping = get_mapping(device);
171 "Attempting to re-initialize sysfs mapping for device\n");
172 put_mapping(mapping);
173 mutex_unlock(&function_mutex);
177 /* Find the first empty entry in the array. */
178 for (map_idx = 0; map_idx < GASKET_SYSFS_NUM_MAPPINGS; ++map_idx) {
179 mutex_lock(&dev_mappings[map_idx].mutex);
180 if (!dev_mappings[map_idx].device)
181 /* Break with the mutex held! */
183 mutex_unlock(&dev_mappings[map_idx].mutex);
186 if (map_idx == GASKET_SYSFS_NUM_MAPPINGS) {
187 dev_err(device, "All mappings have been exhausted\n");
188 mutex_unlock(&function_mutex);
192 dev_dbg(device, "Creating sysfs mapping for device %s\n",
195 mapping = &dev_mappings[map_idx];
196 mapping->attributes = kcalloc(GASKET_SYSFS_MAX_NODES,
197 sizeof(*mapping->attributes),
199 if (!mapping->attributes) {
200 dev_dbg(device, "Unable to allocate sysfs attribute array\n");
201 mutex_unlock(&mapping->mutex);
202 mutex_unlock(&function_mutex);
206 kref_init(&mapping->refcount);
207 mapping->device = get_device(device);
208 mapping->gasket_dev = gasket_dev;
209 mapping->attribute_count = 0;
210 mutex_unlock(&mapping->mutex);
211 mutex_unlock(&function_mutex);
213 /* Don't decrement the refcount here! One open count keeps it alive! */
217 int gasket_sysfs_create_entries(struct device *device,
218 const struct gasket_sysfs_attribute *attrs)
222 struct gasket_sysfs_mapping *mapping = get_mapping(device);
226 "Creating entries for device without first initializing mapping\n");
230 mutex_lock(&mapping->mutex);
231 for (i = 0; attrs[i].attr.attr.name != NULL; i++) {
232 if (mapping->attribute_count == GASKET_SYSFS_MAX_NODES) {
234 "Maximum number of sysfs nodes reached for device\n");
235 mutex_unlock(&mapping->mutex);
236 put_mapping(mapping);
240 ret = device_create_file(device, &attrs[i].attr);
242 dev_dbg(device, "Unable to create device entries\n");
243 mutex_unlock(&mapping->mutex);
244 put_mapping(mapping);
248 mapping->attributes[mapping->attribute_count] = attrs[i];
249 ++mapping->attribute_count;
252 mutex_unlock(&mapping->mutex);
253 put_mapping(mapping);
256 EXPORT_SYMBOL(gasket_sysfs_create_entries);
258 void gasket_sysfs_remove_mapping(struct device *device)
260 struct gasket_sysfs_mapping *mapping = get_mapping(device);
264 "Attempted to remove non-existent sysfs mapping to device\n");
268 put_mapping_n(mapping, 2);
271 struct gasket_dev *gasket_sysfs_get_device_data(struct device *device)
273 struct gasket_sysfs_mapping *mapping = get_mapping(device);
276 dev_err(device, "device not registered\n");
280 return mapping->gasket_dev;
282 EXPORT_SYMBOL(gasket_sysfs_get_device_data);
284 void gasket_sysfs_put_device_data(struct device *device, struct gasket_dev *dev)
286 struct gasket_sysfs_mapping *mapping = get_mapping(device);
291 /* See comment of put_mapping_n() for why the '2' is necessary. */
292 put_mapping_n(mapping, 2);
294 EXPORT_SYMBOL(gasket_sysfs_put_device_data);
296 struct gasket_sysfs_attribute *
297 gasket_sysfs_get_attr(struct device *device, struct device_attribute *attr)
301 struct gasket_sysfs_mapping *mapping = get_mapping(device);
302 struct gasket_sysfs_attribute *attrs = NULL;
307 attrs = mapping->attributes;
308 num_attrs = mapping->attribute_count;
309 for (i = 0; i < num_attrs; ++i) {
310 if (!strcmp(attrs[i].attr.attr.name, attr->attr.name))
314 dev_err(device, "Unable to find match for device_attribute %s\n",
318 EXPORT_SYMBOL(gasket_sysfs_get_attr);
320 void gasket_sysfs_put_attr(struct device *device,
321 struct gasket_sysfs_attribute *attr)
325 struct gasket_sysfs_mapping *mapping = get_mapping(device);
326 struct gasket_sysfs_attribute *attrs = NULL;
331 attrs = mapping->attributes;
332 num_attrs = mapping->attribute_count;
333 for (i = 0; i < num_attrs; ++i) {
334 if (&attrs[i] == attr) {
335 put_mapping_n(mapping, 2);
340 dev_err(device, "Unable to put unknown attribute: %s\n",
341 attr->attr.attr.name);
342 put_mapping(mapping);
344 EXPORT_SYMBOL(gasket_sysfs_put_attr);
346 ssize_t gasket_sysfs_register_store(struct device *device,
347 struct device_attribute *attr,
348 const char *buf, size_t count)
350 ulong parsed_value = 0;
351 struct gasket_sysfs_mapping *mapping;
352 struct gasket_dev *gasket_dev;
353 struct gasket_sysfs_attribute *gasket_attr;
355 if (count < 3 || buf[0] != '0' || buf[1] != 'x') {
357 "sysfs register write format: \"0x<hex value>\"\n");
361 if (kstrtoul(buf, 16, &parsed_value) != 0) {
363 "Unable to parse input as 64-bit hex value: %s\n", buf);
367 mapping = get_mapping(device);
369 dev_err(device, "Device driver may have been removed\n");
373 gasket_dev = mapping->gasket_dev;
375 dev_err(device, "Device driver may have been removed\n");
376 put_mapping(mapping);
380 gasket_attr = gasket_sysfs_get_attr(device, attr);
382 put_mapping(mapping);
386 gasket_dev_write_64(gasket_dev, parsed_value,
387 gasket_attr->data.bar_address.bar,
388 gasket_attr->data.bar_address.offset);
390 if (gasket_attr->write_callback)
391 gasket_attr->write_callback(gasket_dev, gasket_attr,
394 gasket_sysfs_put_attr(device, gasket_attr);
395 put_mapping(mapping);
398 EXPORT_SYMBOL(gasket_sysfs_register_store);