usb: gadget: composite: introduce usb_gstrings_attach()

The USB strings don't (yet) fully work in multiple configs/gadget
environment. The string id is assigned to the descriptor and the struct
usb_strings. We create a copy of the individual descriptor so we don't
clash if we use a function more than once. However, we have only one
struct usb_string for each string.

Currently each function which is used multiple times checks for
"id != 0" and only assigns string ids if it did not happen yet. This
works well if we use the same function multiple times as long as we do
it within the "one" gadget we have. Trouble starts once we use the same
function in a second gadget.

In order to solve this I introduce usb_gstrings_attach(). This function will
crate a copy all structs except for the strings which are not copied.
After the copy it will assign USB ids and attach it to cdev.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Felipe Balbi <balbi@ti.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/include/linux/usb/composite.h b/include/linux/usb/composite.h
index a212ec3e9d69..3c671c1b37f6 100644
--- a/include/linux/usb/composite.h
+++ b/include/linux/usb/composite.h
@@ -375,6 +375,7 @@ struct usb_composite_dev {
         unsigned int                    suspended:1;
         struct usb_device_descriptor    desc;
         struct list_head                configs;
+        struct list_head                gstrings;
         struct usb_composite_driver     *driver;
         u8                              next_string_id;
         char                            *def_manufacturer;
@@ -396,6 +397,9 @@ struct usb_composite_dev {
 extern int usb_string_id(struct usb_composite_dev *c);
 extern int usb_string_ids_tab(struct usb_composite_dev *c,
                               struct usb_string *str);
+extern struct usb_string *usb_gstrings_attach(struct usb_composite_dev *cdev,
+                struct usb_gadget_strings **sp, unsigned n_strings);
+
 extern int usb_string_ids_n(struct usb_composite_dev *c, unsigned n);
 
 extern void composite_disconnect(struct usb_gadget *gadget);