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>

drivers/usb/gadget/composite.c

@@ -28,6 +28,12 @@
  * with the relevant device-wide data.
  */
 
+static struct usb_gadget_strings **get_containers_gs(
+		struct usb_gadget_string_container *uc)
+{
+	return (struct usb_gadget_strings **)uc->stash;
+}
+
 /**
  * next_ep_desc() - advance to the next EP descriptor
  * @t: currect pointer within descriptor array
@@ -904,6 +910,7 @@ static int get_string(struct usb_composite_dev *cdev,
 		void *buf, u16 language, int id)
 {
 	struct usb_composite_driver	*composite = cdev->driver;
+	struct usb_gadget_string_container *uc;
 	struct usb_configuration	*c;
 	struct usb_function		*f;
 	int				len;
@@ -946,6 +953,15 @@ static int get_string(struct usb_composite_dev *cdev,
 		return s->bLength;
 	}
 
+	list_for_each_entry(uc, &cdev->gstrings, list) {
+		struct usb_gadget_strings **sp;
+
+		sp = get_containers_gs(uc);
+		len = lookup_string(sp, buf, language, id);
+		if (len > 0)
+			return len;
+	}
+
 	/* String IDs are device-scoped, so we look up each string
 	 * table we're told about.  These lookups are infrequent;
 	 * simpler-is-better here.
@@ -1031,6 +1047,119 @@ int usb_string_ids_tab(struct usb_composite_dev *cdev, struct usb_string *str)
 }
 EXPORT_SYMBOL_GPL(usb_string_ids_tab);
 
+static struct usb_gadget_string_container *copy_gadget_strings(
+		struct usb_gadget_strings **sp, unsigned n_gstrings,
+		unsigned n_strings)
+{
+	struct usb_gadget_string_container *uc;
+	struct usb_gadget_strings **gs_array;
+	struct usb_gadget_strings *gs;
+	struct usb_string *s;
+	unsigned mem;
+	unsigned n_gs;
+	unsigned n_s;
+	void *stash;
+
+	mem = sizeof(*uc);
+	mem += sizeof(void *) * (n_gstrings + 1);
+	mem += sizeof(struct usb_gadget_strings) * n_gstrings;
+	mem += sizeof(struct usb_string) * (n_strings + 1) * (n_gstrings);
+	uc = kmalloc(mem, GFP_KERNEL);
+	if (!uc)
+		return ERR_PTR(-ENOMEM);
+	gs_array = get_containers_gs(uc);
+	stash = uc->stash;
+	stash += sizeof(void *) * (n_gstrings + 1);
+	for (n_gs = 0; n_gs < n_gstrings; n_gs++) {
+		struct usb_string *org_s;
+
+		gs_array[n_gs] = stash;
+		gs = gs_array[n_gs];
+		stash += sizeof(struct usb_gadget_strings);
+		gs->language = sp[n_gs]->language;
+		gs->strings = stash;
+		org_s = sp[n_gs]->strings;
+
+		for (n_s = 0; n_s < n_strings; n_s++) {
+			s = stash;
+			stash += sizeof(struct usb_string);
+			if (org_s->s)
+				s->s = org_s->s;
+			else
+				s->s = "";
+			org_s++;
+		}
+		s = stash;
+		s->s = NULL;
+		stash += sizeof(struct usb_string);
+
+	}
+	gs_array[n_gs] = NULL;
+	return uc;
+}
+
+/**
+ * usb_gstrings_attach() - attach gadget strings to a cdev and assign ids
+ * @cdev: the device whose string descriptor IDs are being allocated
+ * and attached.
+ * @sp: an array of usb_gadget_strings to attach.
+ * @n_strings: number of entries in each usb_strings array (sp[]->strings)
+ *
+ * This function will create a deep copy of usb_gadget_strings and usb_string
+ * and attach it to the cdev. The actual string (usb_string.s) will not be
+ * copied but only a referenced will be made. The struct usb_gadget_strings
+ * array may contain multiple languges and should be NULL terminated.
+ * The ->language pointer of each struct usb_gadget_strings has to contain the
+ * same amount of entries.
+ * For instance: sp[0] is en-US, sp[1] is es-ES. It is expected that the first
+ * usb_string entry of es-ES containts the translation of the first usb_string
+ * entry of en-US. Therefore both entries become the same id assign.
+ */
+struct usb_string *usb_gstrings_attach(struct usb_composite_dev *cdev,
+		struct usb_gadget_strings **sp, unsigned n_strings)
+{
+	struct usb_gadget_string_container *uc;
+	struct usb_gadget_strings **n_gs;
+	unsigned n_gstrings = 0;
+	unsigned i;
+	int ret;
+
+	for (i = 0; sp[i]; i++)
+		n_gstrings++;
+
+	if (!n_gstrings)
+		return ERR_PTR(-EINVAL);
+
+	uc = copy_gadget_strings(sp, n_gstrings, n_strings);
+	if (IS_ERR(uc))
+		return ERR_PTR(PTR_ERR(uc));
+
+	n_gs = get_containers_gs(uc);
+	ret = usb_string_ids_tab(cdev, n_gs[0]->strings);
+	if (ret)
+		goto err;
+
+	for (i = 1; i < n_gstrings; i++) {
+		struct usb_string *m_s;
+		struct usb_string *s;
+		unsigned n;
+
+		m_s = n_gs[0]->strings;
+		s = n_gs[i]->strings;
+		for (n = 0; n < n_strings; n++) {
+			s->id = m_s->id;
+			s++;
+			m_s++;
+		}
+	}
+	list_add_tail(&uc->list, &cdev->gstrings);
+	return n_gs[0]->strings;
+err:
+	kfree(uc);
+	return ERR_PTR(ret);
+}
+EXPORT_SYMBOL_GPL(usb_gstrings_attach);
+
 /**
  * usb_string_ids_n() - allocate unused string IDs in batch
  * @c: the device whose string descriptor IDs are being allocated
@@ -1377,6 +1506,7 @@ static DEVICE_ATTR(suspended, 0444, composite_show_suspended, NULL);
 static void __composite_unbind(struct usb_gadget *gadget, bool unbind_driver)
 {
 	struct usb_composite_dev	*cdev = get_gadget_data(gadget);
+	struct usb_gadget_string_container *uc, *tmp;
 
 	/* composite_disconnect() must already have been called
 	 * by the underlying peripheral controller driver!
@@ -1391,6 +1521,10 @@ static void __composite_unbind(struct usb_gadget *gadget, bool unbind_driver)
 				struct usb_configuration, list);
 		remove_config(cdev, c);
 	}
+	list_for_each_entry_safe(uc, tmp, &cdev->gstrings, list) {
+		list_del(&uc->list);
+		kfree(uc);
+	}
 	if (cdev->driver->unbind && unbind_driver)
 		cdev->driver->unbind(cdev);
 
@@ -1514,6 +1648,7 @@ static int composite_bind(struct usb_gadget *gadget,
 	cdev->gadget = gadget;
 	set_gadget_data(gadget, cdev);
 	INIT_LIST_HEAD(&cdev->configs);
+	INIT_LIST_HEAD(&cdev->gstrings);
 
 	status = composite_dev_prepare(composite, cdev);
 	if (status)

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);

include/linux/usb/gadget.h

@@ -913,6 +913,11 @@ struct usb_gadget_strings {
 	struct usb_string	*strings;
 };
 
+struct usb_gadget_string_container {
+	struct list_head        list;
+	u8                      *stash[0];
+};
+
 /* put descriptor for string with that id into buf (buflen >= 256) */
 int usb_gadget_get_string(struct usb_gadget_strings *table, int id, u8 *buf);