--- /dev/null
+*How FunctionFS works*
+
+From kernel point of view it is just a composite function with some
+unique behaviour. It may be added to an USB configuration only after
+the user space driver has registered by writing descriptors and
+strings (the user space program has to provide the same information
+that kernel level composite functions provide when they are added to
+the configuration).
+
+This in particular means that the composite initialisation functions
+may not be in init section (ie. may not use the __init tag).
+
+From user space point of view it is a file system which when
+mounted provides an "ep0" file. User space driver need to
+write descriptors and strings to that file. It does not need
+to worry about endpoints, interfaces or strings numbers but
+simply provide descriptors such as if the function was the
+only one (endpoints and strings numbers starting from one and
+interface numbers starting from zero). The FunctionFS changes
+them as needed also handling situation when numbers differ in
+different configurations.
+
+When descriptors and strings are written "ep#" files appear
+(one for each declared endpoint) which handle communication on
+a single endpoint. Again, FunctionFS takes care of the real
+numbers and changing of the configuration (which means that
+"ep1" file may be really mapped to (say) endpoint 3 (and when
+configuration changes to (say) endpoint 2)). "ep0" is used
+for receiving events and handling setup requests.
+
+When all files are closed the function disables itself.
+
+What I also want to mention is that the FunctionFS is designed in such
+a way that it is possible to mount it several times so in the end
+a gadget could use several FunctionFS functions. The idea is that
+each FunctionFS instance is identified by the device name used
+when mounting.
+
+One can imagine a gadget that has an Ethernet, MTP and HID interfaces
+where the last two are implemented via FunctionFS. On user space
+level it would look like this:
+
+$ insmod g_ffs.ko idVendor=<ID> iSerialNumber=<string> functions=mtp,hid
+$ mkdir /dev/ffs-mtp && mount -t functionfs mtp /dev/ffs-mtp
+$ ( cd /dev/ffs-mtp && mtp-daemon ) &
+$ mkdir /dev/ffs-hid && mount -t functionfs hid /dev/ffs-hid
+$ ( cd /dev/ffs-hid && hid-daemon ) &
+
+On kernel level the gadget checks ffs_data->dev_name to identify
+whether it's FunctionFS designed for MTP ("mtp") or HID ("hid").
+
+If no "functions" module parameters is supplied, the driver accepts
+just one function with any name.
+
+When "functions" module parameter is supplied, only functions
+with listed names are accepted. In particular, if the "functions"
+parameter's value is just a one-element list, then the behaviour
+is similar to when there is no "functions" at all; however,
+only a function with the specified name is accepted.
+
+The gadget is registered only after all the declared function
+filesystems have been mounted and USB descriptors of all functions
+have been written to their ep0's.
+
+Conversely, the gadget is unregistered after the first USB function
+closes its endpoints.
+
struct ffs_file_perms perms;
umode_t root_mode;
const char *dev_name;
+ union {
+ /* set by ffs_fs_mount(), read by ffs_sb_fill() */
+ void *private_data;
+ /* set by ffs_sb_fill(), read by ffs_fs_mount */
+ struct ffs_data *ffs_data;
+ };
};
static int ffs_sb_fill(struct super_block *sb, void *_data, int silent)
goto Enomem;
ffs->sb = sb;
- ffs->dev_name = data->dev_name;
+ ffs->dev_name = kstrdup(data->dev_name, GFP_KERNEL);
+ if (unlikely(!ffs->dev_name))
+ goto Enomem;
ffs->file_perms = data->perms;
+ ffs->private_data = data->private_data;
+
+ /* used by the caller of this function */
+ data->ffs_data = ffs;
sb->s_fs_info = ffs;
sb->s_blocksize = PAGE_CACHE_SIZE;
},
.root_mode = S_IFDIR | 0500,
};
+ struct dentry *rv;
int ret;
+ void *ffs_dev;
ENTER();
- ret = functionfs_check_dev_callback(dev_name);
- if (unlikely(ret < 0))
- return ERR_PTR(ret);
-
ret = ffs_fs_parse_opts(&data, opts);
if (unlikely(ret < 0))
return ERR_PTR(ret);
+ ffs_dev = functionfs_acquire_dev_callback(dev_name);
+ if (IS_ERR(ffs_dev))
+ return ffs_dev;
+
data.dev_name = dev_name;
- return mount_single(t, flags, &data, ffs_sb_fill);
+ data.private_data = ffs_dev;
+ rv = mount_nodev(t, flags, &data, ffs_sb_fill);
+
+ /* data.ffs_data is set by ffs_sb_fill */
+ if (IS_ERR(rv))
+ functionfs_release_dev_callback(data.ffs_data);
+
+ return rv;
}
static void
ENTER();
kill_litter_super(sb);
- if (sb->s_fs_info)
+ if (sb->s_fs_info) {
+ functionfs_release_dev_callback(sb->s_fs_info);
ffs_data_put(sb->s_fs_info);
+ }
}
static struct file_system_type ffs_fs_type = {
ffs_data_clear(ffs);
BUG_ON(waitqueue_active(&ffs->ev.waitq) ||
waitqueue_active(&ffs->ep0req_completion.wait));
+ kfree(ffs->dev_name);
kfree(ffs);
}
}
#define GFS_VENDOR_ID 0x1d6b /* Linux Foundation */
#define GFS_PRODUCT_ID 0x0105 /* FunctionFS Gadget */
+#define GFS_MAX_DEVS 10
+
+struct gfs_ffs_obj {
+ const char *name;
+ bool mounted;
+ bool desc_ready;
+ struct ffs_data *ffs_data;
+};
+
static struct usb_device_descriptor gfs_dev_desc = {
.bLength = sizeof gfs_dev_desc,
.bDescriptorType = USB_DT_DEVICE,
.idProduct = cpu_to_le16(GFS_PRODUCT_ID),
};
+static char *func_names[GFS_MAX_DEVS];
+static unsigned int func_num;
+
module_param_named(bDeviceClass, gfs_dev_desc.bDeviceClass, byte, 0644);
MODULE_PARM_DESC(bDeviceClass, "USB Device class");
module_param_named(bDeviceSubClass, gfs_dev_desc.bDeviceSubClass, byte, 0644);
MODULE_PARM_DESC(bDeviceSubClass, "USB Device subclass");
module_param_named(bDeviceProtocol, gfs_dev_desc.bDeviceProtocol, byte, 0644);
MODULE_PARM_DESC(bDeviceProtocol, "USB Device protocol");
+module_param_array_named(functions, func_names, charp, &func_num, 0);
+MODULE_PARM_DESC(functions, "USB Functions list");
static const struct usb_descriptor_header *gfs_otg_desc[] = {
(const struct usb_descriptor_header *)
.iProduct = DRIVER_DESC,
};
-static struct ffs_data *gfs_ffs_data;
-static unsigned long gfs_registered;
+static DEFINE_MUTEX(gfs_lock);
+static unsigned int missing_funcs;
+static bool gfs_ether_setup;
+static bool gfs_registered;
+static bool gfs_single_func;
+static struct gfs_ffs_obj *ffs_tab;
static int __init gfs_init(void)
{
+ int i;
+
ENTER();
+ if (!func_num) {
+ gfs_single_func = true;
+ func_num = 1;
+ }
+
+ ffs_tab = kcalloc(func_num, sizeof *ffs_tab, GFP_KERNEL);
+ if (!ffs_tab)
+ return -ENOMEM;
+
+ if (!gfs_single_func)
+ for (i = 0; i < func_num; i++)
+ ffs_tab[i].name = func_names[i];
+
+ missing_funcs = func_num;
+
return functionfs_init();
}
module_init(gfs_init);
static void __exit gfs_exit(void)
{
ENTER();
+ mutex_lock(&gfs_lock);
- if (test_and_clear_bit(0, &gfs_registered))
+ if (gfs_registered)
usb_composite_unregister(&gfs_driver);
+ gfs_registered = false;
functionfs_cleanup();
+
+ mutex_unlock(&gfs_lock);
+ kfree(ffs_tab);
}
module_exit(gfs_exit);
+static struct gfs_ffs_obj *gfs_find_dev(const char *dev_name)
+{
+ int i;
+
+ ENTER();
+
+ if (gfs_single_func)
+ return &ffs_tab[0];
+
+ for (i = 0; i < func_num; i++)
+ if (strcmp(ffs_tab[i].name, dev_name) == 0)
+ return &ffs_tab[i];
+
+ return NULL;
+}
+
static int functionfs_ready_callback(struct ffs_data *ffs)
{
+ struct gfs_ffs_obj *ffs_obj;
int ret;
ENTER();
+ mutex_lock(&gfs_lock);
+
+ ffs_obj = ffs->private_data;
+ if (!ffs_obj) {
+ ret = -EINVAL;
+ goto done;
+ }
+
+ if (WARN_ON(ffs_obj->desc_ready)) {
+ ret = -EBUSY;
+ goto done;
+ }
+ ffs_obj->desc_ready = true;
+ ffs_obj->ffs_data = ffs;
- if (WARN_ON(test_and_set_bit(0, &gfs_registered)))
- return -EBUSY;
+ if (--missing_funcs) {
+ ret = 0;
+ goto done;
+ }
+
+ if (gfs_registered) {
+ ret = -EBUSY;
+ goto done;
+ }
+ gfs_registered = true;
- gfs_ffs_data = ffs;
ret = usb_composite_probe(&gfs_driver, gfs_bind);
if (unlikely(ret < 0))
- clear_bit(0, &gfs_registered);
+ gfs_registered = false;
+
+done:
+ mutex_unlock(&gfs_lock);
return ret;
}
static void functionfs_closed_callback(struct ffs_data *ffs)
{
+ struct gfs_ffs_obj *ffs_obj;
+
ENTER();
+ mutex_lock(&gfs_lock);
- if (test_and_clear_bit(0, &gfs_registered))
+ ffs_obj = ffs->private_data;
+ if (!ffs_obj)
+ goto done;
+
+ ffs_obj->desc_ready = false;
+ missing_funcs++;
+
+ if (gfs_registered)
usb_composite_unregister(&gfs_driver);
+ gfs_registered = false;
+
+done:
+ mutex_unlock(&gfs_lock);
}
-static int functionfs_check_dev_callback(const char *dev_name)
+static void *functionfs_acquire_dev_callback(const char *dev_name)
{
- return 0;
+ struct gfs_ffs_obj *ffs_dev;
+
+ ENTER();
+ mutex_lock(&gfs_lock);
+
+ ffs_dev = gfs_find_dev(dev_name);
+ if (!ffs_dev) {
+ ffs_dev = ERR_PTR(-ENODEV);
+ goto done;
+ }
+
+ if (ffs_dev->mounted) {
+ ffs_dev = ERR_PTR(-EBUSY);
+ goto done;
+ }
+ ffs_dev->mounted = true;
+
+done:
+ mutex_unlock(&gfs_lock);
+ return ffs_dev;
}
+static void functionfs_release_dev_callback(struct ffs_data *ffs_data)
+{
+ struct gfs_ffs_obj *ffs_dev;
+
+ ENTER();
+ mutex_lock(&gfs_lock);
+
+ ffs_dev = ffs_data->private_data;
+ if (ffs_dev)
+ ffs_dev->mounted = false;
+
+ mutex_unlock(&gfs_lock);
+}
+
+/*
+ * It is assumed that gfs_bind is called from a context where gfs_lock is held
+ */
static int gfs_bind(struct usb_composite_dev *cdev)
{
int ret, i;
ENTER();
- if (WARN_ON(!gfs_ffs_data))
+ if (missing_funcs)
return -ENODEV;
ret = gether_setup(cdev->gadget, gfs_hostaddr);
if (unlikely(ret < 0))
goto error_quick;
+ gfs_ether_setup = true;
ret = usb_string_ids_tab(cdev, gfs_strings);
if (unlikely(ret < 0))
goto error;
- ret = functionfs_bind(gfs_ffs_data, cdev);
- if (unlikely(ret < 0))
- goto error;
+ for (i = func_num; --i; ) {
+ ret = functionfs_bind(ffs_tab[i].ffs_data, cdev);
+ if (unlikely(ret < 0)) {
+ while (++i < func_num)
+ functionfs_unbind(ffs_tab[i].ffs_data);
+ goto error;
+ }
+ }
for (i = 0; i < ARRAY_SIZE(gfs_configurations); ++i) {
struct gfs_configuration *c = gfs_configurations + i;
return 0;
error_unbind:
- functionfs_unbind(gfs_ffs_data);
+ for (i = 0; i < func_num; i++)
+ functionfs_unbind(ffs_tab[i].ffs_data);
error:
gether_cleanup();
error_quick:
- gfs_ffs_data = NULL;
+ gfs_ether_setup = false;
return ret;
}
+/*
+ * It is assumed that gfs_unbind is called from a context where gfs_lock is held
+ */
static int gfs_unbind(struct usb_composite_dev *cdev)
{
+ int i;
+
ENTER();
/*
* from composite on orror recovery, but what you're gonna
* do...?
*/
- if (gfs_ffs_data) {
+ if (gfs_ether_setup)
gether_cleanup();
- functionfs_unbind(gfs_ffs_data);
- gfs_ffs_data = NULL;
- }
+ gfs_ether_setup = false;
+
+ for (i = func_num; --i; )
+ if (ffs_tab[i].ffs_data)
+ functionfs_unbind(ffs_tab[i].ffs_data);
return 0;
}
+/*
+ * It is assumed that gfs_do_config is called from a context where
+ * gfs_lock is held
+ */
static int gfs_do_config(struct usb_configuration *c)
{
struct gfs_configuration *gc =
container_of(c, struct gfs_configuration, c);
+ int i;
int ret;
- if (WARN_ON(!gfs_ffs_data))
+ if (missing_funcs)
return -ENODEV;
if (gadget_is_otg(c->cdev->gadget)) {
return ret;
}
- ret = functionfs_bind_config(c->cdev, c, gfs_ffs_data);
- if (unlikely(ret < 0))
- return ret;
+ for (i = 0; i < func_num; i++) {
+ ret = functionfs_bind_config(c->cdev, c, ffs_tab[i].ffs_data);
+ if (unlikely(ret < 0))
+ return ret;
+ }
/*
* After previous do_configs there may be some invalid
projects / ~andy / linux / commitdiff