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usb: gadget: configfs: Support arbitrary string descriptors
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@ideasonboard.com> Link: https://lore.kernel.org/r/20230206161802.892954-7-dan.scally@ideasonboard.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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@ -90,6 +90,16 @@ Then the strings can be specified::
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$ echo <manufacturer> > strings/0x409/manufacturer
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$ echo <product> > strings/0x409/product
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Further custom string descriptors can be created as directories within the
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language's directory, with the string text being written to the "s" attribute
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within the string's directory:
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$ mkdir strings/0x409/xu.0
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$ echo <string text> > strings/0x409/xu.0/s
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Where function drivers support it, functions may allow symlinks to these custom
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string descriptors to associate those strings with class descriptors.
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2. Creating the configurations
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------------------------------
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@ -95,6 +95,8 @@ struct gadget_language {
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struct config_group group;
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struct list_head list;
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struct list_head gadget_strings;
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unsigned int nstrings;
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};
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struct gadget_config_name {
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@ -791,8 +793,174 @@ static void gadget_language_attr_release(struct config_item *item)
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kfree(gs);
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}
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USB_CONFIG_STRING_RW_OPS(gadget_language);
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USB_CONFIG_STRINGS_LANG(gadget_language, gadget_info);
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static struct configfs_item_operations gadget_language_langid_item_ops = {
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.release = gadget_language_attr_release,
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};
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static ssize_t gadget_string_id_show(struct config_item *item, char *page)
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{
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struct gadget_string *string = to_gadget_string(item);
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int ret;
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ret = sprintf(page, "%u\n", string->usb_string.id);
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return ret;
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}
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CONFIGFS_ATTR_RO(gadget_string_, id);
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static ssize_t gadget_string_s_show(struct config_item *item, char *page)
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{
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struct gadget_string *string = to_gadget_string(item);
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int ret;
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ret = snprintf(page, sizeof(string->string), "%s\n", string->string);
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return ret;
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}
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static ssize_t gadget_string_s_store(struct config_item *item, const char *page,
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size_t len)
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{
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struct gadget_string *string = to_gadget_string(item);
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int size = min(sizeof(string->string), len + 1);
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int ret;
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if (len > USB_MAX_STRING_LEN)
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return -EINVAL;
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ret = strscpy(string->string, page, size);
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return len;
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}
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CONFIGFS_ATTR(gadget_string_, s);
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static struct configfs_attribute *gadget_string_attrs[] = {
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&gadget_string_attr_id,
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&gadget_string_attr_s,
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NULL,
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};
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static void gadget_string_release(struct config_item *item)
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{
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struct gadget_string *string = to_gadget_string(item);
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kfree(string);
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}
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static struct configfs_item_operations gadget_string_item_ops = {
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.release = gadget_string_release,
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};
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static const struct config_item_type gadget_string_type = {
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.ct_item_ops = &gadget_string_item_ops,
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.ct_attrs = gadget_string_attrs,
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.ct_owner = THIS_MODULE,
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};
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static struct config_item *gadget_language_string_make(struct config_group *group,
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const char *name)
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{
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struct gadget_language *language;
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struct gadget_string *string;
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language = to_gadget_language(&group->cg_item);
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string = kzalloc(sizeof(*string), GFP_KERNEL);
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if (!string)
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return ERR_PTR(-ENOMEM);
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string->usb_string.id = language->nstrings++;
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string->usb_string.s = string->string;
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list_add_tail(&string->list, &language->gadget_strings);
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config_item_init_type_name(&string->item, name, &gadget_string_type);
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return &string->item;
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}
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static void gadget_language_string_drop(struct config_group *group,
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struct config_item *item)
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{
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struct gadget_language *language;
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struct gadget_string *string;
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unsigned int i = USB_GADGET_FIRST_AVAIL_IDX;
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language = to_gadget_language(&group->cg_item);
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string = to_gadget_string(item);
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list_del(&string->list);
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language->nstrings--;
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/* Reset the ids for the language's strings to guarantee a continuous set */
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list_for_each_entry(string, &language->gadget_strings, list)
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string->usb_string.id = i++;
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}
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static struct configfs_group_operations gadget_language_langid_group_ops = {
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.make_item = gadget_language_string_make,
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.drop_item = gadget_language_string_drop,
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};
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static struct config_item_type gadget_language_type = {
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.ct_item_ops = &gadget_language_langid_item_ops,
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.ct_group_ops = &gadget_language_langid_group_ops,
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.ct_attrs = gadget_language_langid_attrs,
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.ct_owner = THIS_MODULE,
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};
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static struct config_group *gadget_language_make(struct config_group *group,
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const char *name)
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{
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struct gadget_info *gi;
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struct gadget_language *gs;
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struct gadget_language *new;
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int langs = 0;
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int ret;
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new = kzalloc(sizeof(*new), GFP_KERNEL);
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if (!new)
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return ERR_PTR(-ENOMEM);
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ret = check_user_usb_string(name, &new->stringtab_dev);
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if (ret)
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goto err;
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config_group_init_type_name(&new->group, name,
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&gadget_language_type);
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gi = container_of(group, struct gadget_info, strings_group);
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ret = -EEXIST;
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list_for_each_entry(gs, &gi->string_list, list) {
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if (gs->stringtab_dev.language == new->stringtab_dev.language)
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goto err;
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langs++;
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}
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ret = -EOVERFLOW;
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if (langs >= MAX_USB_STRING_LANGS)
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goto err;
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list_add_tail(&new->list, &gi->string_list);
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INIT_LIST_HEAD(&new->gadget_strings);
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/* We have the default manufacturer, product and serialnumber strings */
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new->nstrings = 3;
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return &new->group;
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err:
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kfree(new);
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return ERR_PTR(ret);
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}
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static void gadget_language_drop(struct config_group *group,
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struct config_item *item)
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{
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config_item_put(item);
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}
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static struct configfs_group_operations gadget_language_group_ops = {
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.make_group = &gadget_language_make,
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.drop_item = &gadget_language_drop,
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};
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static struct config_item_type gadget_language_strings_type = {
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.ct_group_ops = &gadget_language_group_ops,
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.ct_owner = THIS_MODULE,
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};
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static inline struct gadget_info *webusb_item_to_gadget_info(
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struct config_item *item)
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@ -15,6 +15,7 @@
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#ifndef __LINUX_USB_GADGET_H
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#define __LINUX_USB_GADGET_H
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#include <linux/configfs.h>
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#include <linux/device.h>
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#include <linux/errno.h>
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#include <linux/init.h>
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@ -821,6 +822,16 @@ int usb_gadget_get_string(const struct usb_gadget_strings *table, int id, u8 *bu
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/* check if the given language identifier is valid */
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bool usb_validate_langid(u16 langid);
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struct gadget_string {
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struct config_item item;
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struct list_head list;
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char string[USB_MAX_STRING_LEN];
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struct usb_string usb_string;
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};
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#define to_gadget_string(str_item)\
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container_of(str_item, struct gadget_string, item)
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/*-------------------------------------------------------------------------*/
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/* utility to simplify managing config descriptors */
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