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Commit 311fa89d authored by Jack Pham's avatar Jack Pham Committed by Matt Wagantall
Browse files

usb: composite: Reuse existing strings in usb_gstrings_attach 



A function driver may call usb_gstrings_attach() when being
bound to a composite configuration in order to reserve string
IDs for its strings. However, if the function is unbound and
rebound to the same composite device (in cases of dynamic
composition switching), repeated calls to usb_gstrings_attach()
may exhaust the 255 available string IDs. In this case first
check if the cdev already contains the same strings being added,
and if so just reuse them and their previously allocated IDs.

Change-Id: I975a6a2989cb296d4f9c732389ee6241c7e087c4
Signed-off-by: default avatarJack Pham <jackp@codeaurora.org>
parent bee2e1b3

drivers/usb/gadget/composite.c

+45 −0
Original line number Diff line number Diff line
@@ -1317,6 +1317,44 @@ static struct usb_gadget_string_container *copy_gadget_strings( 
	return uc;

}



static struct usb_gadget_string_container *find_gadget_strings(

		struct usb_composite_dev *cdev,

		struct usb_gadget_strings **sp, unsigned n_strings)

{

	struct usb_gadget_string_container *uc;



	list_for_each_entry(uc, &cdev->gstrings, list) {

		struct usb_gadget_strings **org_gs;

		struct usb_string *org_s, *s;

		int i;



		org_gs = get_containers_gs(uc);



		/*

		 * only check the first language since it's not likely that a

		 * set of strings matches one language but not others

		 */

		if (sp[0]->language != org_gs[0]->language)

			continue;



		org_s = org_gs[0]->strings;

		s = sp[0]->strings;



		for (i = 0; i < n_strings; i++) {

			if ((s->s != org_s->s) && !(!s->s && *org_s->s == '\0'))

				break;



			org_s++;

			s++;

		}



		if (i == n_strings)

			return uc;

	}



	return NULL;

}



/**

 * usb_gstrings_attach() - attach gadget strings to a cdev and assign ids

 * @cdev: the device whose string descriptor IDs are being allocated
@@ -1349,6 +1387,13 @@ struct usb_string *usb_gstrings_attach(struct usb_composite_dev *cdev, 
	if (!n_gstrings)

		return ERR_PTR(-EINVAL);



	/* check if same strings added to cdev already, if so just reuse them */

	uc = find_gadget_strings(cdev, sp, n_strings);

	if (uc) {

		n_gs = get_containers_gs(uc);

		return n_gs[0]->strings;

	}



	uc = copy_gadget_strings(sp, n_gstrings, n_strings);

	if (IS_ERR(uc))

		return ERR_CAST(uc);