usb gadget: descriptor copying support

Define three new descriptor manipulation utilities, for use when
setting up functions that may have multiple instances:

	usb_copy_descriptors() to copy a vector of descriptors
	usb_free_descriptors() to free the copy
	usb_find_endpoint() to find a copied version

These will be used as follows.  Functions will continue to have static
tables of descriptors they update, now used as __initdata templates.

When a function creates a new instance, it patches those tables with
relevant interface and string IDs, plus endpoint assignments.  Then it
copies those morphed descriptors, associates the copies with the new
function instance, and records the endpoint descriptors to use when
activating the endpoints.  When initialization is done, only the copies
remain in memory.  The copies are freed on driver removal.

This ensures that each instance has descriptors which hold the right
instance-specific data.  Two instances in the same configuration will
obviously never share the same interface IDs or use the same endpoints.
Instances in different configurations won't do so either, which means
this is slightly less memory-efficient in some cases.

This also includes a bugfix to the epautoconf code that shows up with
this usage model.  It must replace the previous endpoint number when
updating the template descriptors, not just mask in a few more bits.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 75 insertions, 1 deletions

diff --git a/drivers/usb/gadget/config.c b/drivers/usb/gadget/config.c
index a4e54b2743f0..1ca1c326392a 100644
--- a/drivers/usb/gadget/config.c
+++ b/drivers/usb/gadget/config.c
@@ -96,7 +96,7 @@ int usb_gadget_config_buf(
 	/* config descriptor first */
 	if (length < USB_DT_CONFIG_SIZE || !desc)
 		return -EINVAL;
-	*cp = *config; 
+	*cp = *config;
 
 	/* then interface/endpoint/class/vendor/... */
 	len = usb_descriptor_fillbuf(USB_DT_CONFIG_SIZE + (u8*)buf,
@@ -115,3 +115,77 @@ int usb_gadget_config_buf(
 	return len;
 }
 
+/**
+ * usb_copy_descriptors - copy a vector of USB descriptors
+ * @src: null-terminated vector to copy
+ * Context: initialization code, which may sleep
+ *
+ * This makes a copy of a vector of USB descriptors.  Its primary use
+ * is to support usb_function objects which can have multiple copies,
+ * each needing different descriptors.  Functions may have static
+ * tables of descriptors, which are used as templates and customized
+ * with identifiers (for interfaces, strings, endpoints, and more)
+ * as needed by a given function instance.
+ */
+struct usb_descriptor_header **__init
+usb_copy_descriptors(struct usb_descriptor_header **src)
+{
+	struct usb_descriptor_header **tmp;
+	unsigned bytes;
+	unsigned n_desc;
+	void *mem;
+	struct usb_descriptor_header **ret;
+
+	/* count descriptors and their sizes; then add vector size */
+	for (bytes = 0, n_desc = 0, tmp = src; *tmp; tmp++, n_desc++)
+		bytes += (*tmp)->bLength;
+	bytes += (n_desc + 1) * sizeof(*tmp);
+
+	mem = kmalloc(bytes, GFP_KERNEL);
+	if (!mem)
+		return NULL;
+
+	/* fill in pointers starting at "tmp",
+	 * to descriptors copied starting at "mem";
+	 * and return "ret"
+	 */
+	tmp = mem;
+	ret = mem;
+	mem += (n_desc + 1) * sizeof(*tmp);
+	while (*src) {
+		memcpy(mem, *src, (*src)->bLength);
+		*tmp = mem;
+		tmp++;
+		mem += (*src)->bLength;
+		src++;
+	}
+	*tmp = NULL;
+
+	return ret;
+}
+
+/**
+ * usb_find_endpoint - find a copy of an endpoint descriptor
+ * @src: original vector of descriptors
+ * @copy: copy of @src
+ * @ep: endpoint descriptor found in @src
+ *
+ * This returns the copy of the @match descriptor made for @copy.  Its
+ * intended use is to help remembering the endpoint descriptor to use
+ * when enabling a given endpoint.
+ */
+struct usb_endpoint_descriptor *__init
+usb_find_endpoint(
+	struct usb_descriptor_header **src,
+	struct usb_descriptor_header **copy,
+	struct usb_endpoint_descriptor *match
+)
+{
+	while (*src) {
+		if (*src == (void *) match)
+			return (void *)*copy;
+		src++;
+		copy++;
+	}
+	return NULL;
+}