Add a framework to allow users to define arbitrary string descriptors
for a USB Gadget. This is modelled as a new type of config item rather
than as hardcoded attributes so as to be as flexible as possible.
Signed-off-by: Daniel Scally <dan.scally@xxxxxxxxxxxxxxxx>
---
Changes in v5:
- None
Changes in v4:
- Added some explanatory documentation (Alan)
Changes in v3:
- Moved this functionality from the UVC function to usb gadget core.
Changes in v2:
- New patch
Documentation/usb/gadget_configfs.rst | 10 ++
drivers/usb/gadget/configfs.c | 172 +++++++++++++++++++++++++-
include/linux/usb/gadget.h | 11 ++
3 files changed, 191 insertions(+), 2 deletions(-)
diff --git a/Documentation/usb/gadget_configfs.rst b/Documentation/usb/gadget_configfs.rst
index e4566ffb223f..868e118a2644 100644
--- a/Documentation/usb/gadget_configfs.rst
+++ b/Documentation/usb/gadget_configfs.rst
@@ -90,6 +90,16 @@ Then the strings can be specified::
$ echo <manufacturer> > strings/0x409/manufacturer
$ echo <product> > strings/0x409/product
+Further custom string descriptors can be created as directories within the
+language's directory, with the string text being written to the "s" attribute
+within the string's directory:
+
+ $ mkdir strings/0x409/xu.0
+ $ echo <string text> > strings/0x409/xu.0/s
+
+Where function drivers support it, functions may allow symlinks to these custom
+string descriptors to associate those strings with class descriptors.
+
2. Creating the configurations
------------------------------
diff --git a/drivers/usb/gadget/configfs.c b/drivers/usb/gadget/configfs.c
index 3beeafcf2e3b..ac275855eeb6 100644
--- a/drivers/usb/gadget/configfs.c
+++ b/drivers/usb/gadget/configfs.c
@@ -95,6 +95,8 @@ struct gadget_language {
struct config_group group;
struct list_head list;
+ struct list_head gadget_strings;
+ unsigned int nstrings;
};
struct gadget_config_name {
@@ -791,8 +793,174 @@ static void gadget_language_attr_release(struct config_item *item)
kfree(gs);
}
-USB_CONFIG_STRING_RW_OPS(gadget_language);
-USB_CONFIG_STRINGS_LANG(gadget_language, gadget_info);
+static struct configfs_item_operations gadget_language_langid_item_ops = {
+ .release = gadget_language_attr_release,
+};
+
+static ssize_t gadget_string_id_show(struct config_item *item, char *page)
+{
+ struct gadget_string *string = to_gadget_string(item);
+ int ret;
+
+ ret = sprintf(page, "%u\n", string->usb_string.id);
+ return ret;
+}
+CONFIGFS_ATTR_RO(gadget_string_, id);
+
+static ssize_t gadget_string_s_show(struct config_item *item, char *page)
+{
+ struct gadget_string *string = to_gadget_string(item);
+ int ret;
+
+ ret = snprintf(page, sizeof(string->string), "%s\n", string->string);
+ return ret;
+}
+
+static ssize_t gadget_string_s_store(struct config_item *item, const char *page,
+ size_t len)
+{
+ struct gadget_string *string = to_gadget_string(item);
+ int size = min(sizeof(string->string), len + 1);
+ int ret;
+
+ if (len > USB_MAX_STRING_LEN)
+ return -EINVAL;
+
+ ret = strscpy(string->string, page, size);
+ return len;
+}
+CONFIGFS_ATTR(gadget_string_, s);
+
+static struct configfs_attribute *gadget_string_attrs[] = {
+ &gadget_string_attr_id,
+ &gadget_string_attr_s,
+ NULL,
+};
+
+static void gadget_string_release(struct config_item *item)
+{
+ struct gadget_string *string = to_gadget_string(item);
+
+ kfree(string);
+}
+
+static struct configfs_item_operations gadget_string_item_ops = {
+ .release = gadget_string_release,
+};
+
+static const struct config_item_type gadget_string_type = {
+ .ct_item_ops = &gadget_string_item_ops,
+ .ct_attrs = gadget_string_attrs,
+ .ct_owner = THIS_MODULE,
+};
+
+static struct config_item *gadget_language_string_make(struct config_group *group,
+ const char *name)
+{
+ struct gadget_language *language;
+ struct gadget_string *string;
+
+ language = to_gadget_language(&group->cg_item);
+
+ string = kzalloc(sizeof(*string), GFP_KERNEL);
+ if (!string)
+ return ERR_PTR(-ENOMEM);
+
+ string->usb_string.id = language->nstrings++;
+ string->usb_string.s = string->string;
+ list_add_tail(&string->list, &language->gadget_strings);
+
+ config_item_init_type_name(&string->item, name, &gadget_string_type);
+
+ return &string->item;
+}
+
+static void gadget_language_string_drop(struct config_group *group,
+ struct config_item *item)
+{
+ struct gadget_language *language;
+ struct gadget_string *string;
+ unsigned int i = USB_GADGET_FIRST_AVAIL_IDX;
+
+ language = to_gadget_language(&group->cg_item);
+ string = to_gadget_string(item);
+
+ list_del(&string->list);
+ language->nstrings--;
+
+ /* Reset the ids for the language's strings to guarantee a continuous set */
+ list_for_each_entry(string, &language->gadget_strings, list)
+ string->usb_string.id = i++;
+}
+
+static struct configfs_group_operations gadget_language_langid_group_ops = {
+ .make_item = gadget_language_string_make,
+ .drop_item = gadget_language_string_drop,
+};
+
+static struct config_item_type gadget_language_type = {
+ .ct_item_ops = &gadget_language_langid_item_ops,
+ .ct_group_ops = &gadget_language_langid_group_ops,
+ .ct_attrs = gadget_language_langid_attrs,
+ .ct_owner = THIS_MODULE,
+};
+
+static struct config_group *gadget_language_make(struct config_group *group,
+ const char *name)
+{
+ struct gadget_info *gi;
+ struct gadget_language *gs;
+ struct gadget_language *new;
+ int langs = 0;
+ int ret;
+
+ new = kzalloc(sizeof(*new), GFP_KERNEL);
+ if (!new)
+ return ERR_PTR(-ENOMEM);
+
+ ret = check_user_usb_string(name, &new->stringtab_dev);
+ if (ret)
+ goto err;
+ config_group_init_type_name(&new->group, name,
+ &gadget_language_type);
+
+ gi = container_of(group, struct gadget_info, strings_group);
+ ret = -EEXIST;
+ list_for_each_entry(gs, &gi->string_list, list) {
+ if (gs->stringtab_dev.language == new->stringtab_dev.language)
+ goto err;
+ langs++;
+ }
+ ret = -EOVERFLOW;
+ if (langs >= MAX_USB_STRING_LANGS)
+ goto err;
+
+ list_add_tail(&new->list, &gi->string_list);
+ INIT_LIST_HEAD(&new->gadget_strings);
+
+ /* We have the default manufacturer, product and serialnumber strings */
+ new->nstrings = 3;
+ return &new->group;
+err:
+ kfree(new);
+ return ERR_PTR(ret);
+}
+
+static void gadget_language_drop(struct config_group *group,
+ struct config_item *item)
+{
+ config_item_put(item);
+}
+
+static struct configfs_group_operations gadget_language_group_ops = {
+ .make_group = &gadget_language_make,
+ .drop_item = &gadget_language_drop,
+};
+
+static struct config_item_type gadget_language_strings_type = {
+ .ct_group_ops = &gadget_language_group_ops,
+ .ct_owner = THIS_MODULE,
+};
static inline struct gadget_info *webusb_item_to_gadget_info(
struct config_item *item)
diff --git a/include/linux/usb/gadget.h b/include/linux/usb/gadget.h
index dc3092cea99e..00750f7020f3 100644
--- a/include/linux/usb/gadget.h
+++ b/include/linux/usb/gadget.h
@@ -15,6 +15,7 @@
#ifndef __LINUX_USB_GADGET_H
#define __LINUX_USB_GADGET_H
+#include <linux/configfs.h>
#include <linux/device.h>
#include <linux/errno.h>
#include <linux/init.h>
@@ -821,6 +822,16 @@ int usb_gadget_get_string(const struct usb_gadget_strings *table, int id, u8 *bu
/* check if the given language identifier is valid */
bool usb_validate_langid(u16 langid);
+struct gadget_string {
+ struct config_item item;
+ struct list_head list;
+ char string[USB_MAX_STRING_LEN];
+ struct usb_string usb_string;
+};
+
+#define to_gadget_string(str_item)\
+container_of(str_item, struct gadget_string, item)
+
/*-------------------------------------------------------------------------*/
/* utility to simplify managing config descriptors */
--
2.34.1
