[PATCH v4 06/43] usb: gadget: composite: introduce new descriptors format

[Robert Baldyga]

Introduce new structures designed to contain information about
descriptors. It splits descriptors in two categories:
1. Entity descs - interface and endpoint descriptors
2. Vendor descs - all other vendor and class specific descriptors

Entity descriptors are embedded in hierarchy of structures while vendor
descriptors are contained in linked lists. This distinction is caused
by fact, that entity descriptors are needed during gadget bind procedure,
while vendor descriptors can be supplied later, which is usually desired,
as these descriptors may need to be filled with interface numbers and
endpoint addresses which are assigned during gadget bind.

In result we can split descriptors creation process in two steps - first
collecs entity descriptors, perform the bind and then update and attach
all other descriptors. This process can be done this way not only for
each function separately, but also for entire gadget at once, which means
we can first gather descriptors from all functions in gadget, next perform
bind procedure, and then allow functions to supply additional descriptors.

It allows us to have autoconfig solver capable to better distibute ep
resources, and additionally, because we now store information about
endpoints, allows us to handle endpoint state inside composite framework,
and in result remove lots of boilerplate code from USB functions.

Signed-off-by: Robert Baldyga <r.baldyga@xxxxxxxxxxx>
---
 include/linux/usb/composite.h | 126 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 126 insertions(+)

diff --git a/include/linux/usb/composite.h b/include/linux/usb/composite.h
index 9911c29..8bb5c35 100644
--- a/include/linux/usb/composite.h
+++ b/include/linux/usb/composite.h
@@ -57,6 +57,128 @@
 struct usb_configuration;
 
 /**
+ * struct usb_composite_vendor_desc - vendor specific descriptor
+ * @desc: pointer to vendor specific descriptor
+ * @list: descriptor list element
+ *
+ * It's designed to be element of vendor specific descriptor list,
+ * which can be attached to function, interface (per altsetting) or
+ * endpoint.
+ */
+struct usb_composite_vendor_desc {
+	struct usb_descriptor_header *desc;
+	struct list_head list;
+};
+
+/**
+ * struct usb_composite_ep - representation of USB endpoint
+ * @fs.desc: FullSpeed descriptor
+ * @hs.desc: HighSpeed descriptor
+ * @ss.desc: SuperSpeed descriptor
+ * @ss_comp.desc: SuperSpeed Companion descriptor
+ * @vendor_descs: list of vendor specific descriptors
+ * @vendor_descs_num: count of vendor specific descriptors
+ * @ep: pointer to endpoint obtained during bind process
+ *
+ * We have pointer to each descriptor in union with pointer to descriptor
+ * header in order to avoid casting in many places in code, because in
+ * some situations we want to have access to fields of particular type
+ * of descriptor, while in other situations we want to treat all types
+ * of descriptors in the same way.
+ */
+struct usb_composite_ep {
+	union {
+		struct usb_descriptor_header *header;
+		struct usb_endpoint_descriptor *desc;
+	} fs;
+
+	union {
+		struct usb_descriptor_header *header;
+		struct usb_endpoint_descriptor *desc;
+	} hs;
+
+	union {
+		struct usb_descriptor_header *header;
+		struct usb_endpoint_descriptor *desc;
+	} ss;
+
+	union {
+		struct usb_descriptor_header *header;
+		struct usb_ss_ep_comp_descriptor *desc;
+	} ss_comp;
+
+	struct list_head vendor_descs;
+	int vendor_descs_num;
+
+	struct usb_ep *ep;
+};
+
+/**
+ * struct usb_composite_altset - representation of USB altsetting
+ * @alt.desc: interface (altsetting) descriptor
+ * @eps: array of endpoints in altsetting
+ * @eps_num: number of endpoints
+ * @vendor_descs: list of vendor specific descriptors
+ * @vendor_descs_num: count of vendor specific descriptors
+ *
+ * We have pointer to alt descriptor in union with pointer to descriptor
+ * header in order to avoid casting in many places in code, because in
+ * some situations we want to have access to fields of particular type
+ * of descriptor, while in other situations we want to treat all types
+ * of descriptors in the same way.
+ */
+struct usb_composite_altset {
+	union {
+		struct usb_descriptor_header *header;
+		struct usb_interface_descriptor *desc;
+	} alt;
+
+	struct usb_composite_ep **eps;
+	int eps_num;
+
+	struct list_head vendor_descs;
+	int vendor_descs_num;
+};
+
+/**
+ * struct usb_composite_intf - representation of USB interface
+ * @altsets: array of altsettings in interface
+ * @altsets_num: number of altsettings
+ * @cur_altset: number of currently selected altsetting
+ * @id: id number of interface in configuraion (value of
+ *	bInterfaceNumber in interface descriptor)
+ */
+struct usb_composite_intf {
+	struct usb_composite_altset **altsets;
+	int altsets_num;
+
+	int cur_altset;
+	u8 id;
+};
+
+/**
+ * struct usb_composite_descs - representation of USB descriptors
+ * @intfs: array of interfaces in function
+ * @intfs_num: number of interfaces
+ * @vendor_descs: list of vendor specific descriptors
+ * @vendor_descs_num: count of vendor specific descriptors
+ * @fullspeed: descriptors support FullSpeed
+ * @highspeed: descriptors support HighSpeed
+ * @superspeed: descriptors support SuperSpeed
+ */
+struct usb_composite_descs {
+	struct usb_composite_intf **intfs;
+	int intfs_num;
+
+	struct list_head vendor_descs;
+	int vendor_descs_num;
+
+	unsigned fullspeed:1;
+	unsigned highspeed:1;
+	unsigned superspeed:1;
+};
+
+/**
  * struct usb_os_desc_ext_prop - describes one "Extended Property"
  * @entry: used to keep a list of extended properties
  * @type: Extended Property type
@@ -126,6 +248,8 @@ struct usb_os_desc_table {
  *	string identifiers assigned during @bind(). If this
  *	pointer is null after initiation, the function will not
  *	be available at super speed.
+ * @descs: structure containing information about descriptors and endpoints
+ *	assigned during gadget bind.
  * @config: assigned when @usb_add_function() is called; this is the
  *	configuration with which this function is associated.
  * @os_desc_table: Table of (interface id, os descriptors) pairs. The function
@@ -187,6 +311,8 @@ struct usb_function {
 	struct usb_descriptor_header	**hs_descriptors;
 	struct usb_descriptor_header	**ss_descriptors;
 
+	struct usb_composite_descs	*descs;
+
 	struct usb_configuration	*config;
 
 	struct usb_os_desc_table	*os_desc_table;
-- 
1.9.1