usb: gadget: configure endpoint according to gadget speed

Add config_ep_by_speed() to configure the endpoint
according to the gadget speed.

Using this function will spare the FDs from handling
the endpoint chosen descriptor.

Signed-off-by: Tatyana Brokhman <tlinder@codeaurora.org>
Signed-off-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 85 insertions, 0 deletions

diff --git a/drivers/usb/gadget/composite.c b/drivers/usb/gadget/composite.c
index 5cbb1a41c223..1c6bd666150a 100644
--- a/drivers/usb/gadget/composite.c
+++ b/drivers/usb/gadget/composite.c
@@ -74,6 +74,91 @@ MODULE_PARM_DESC(iSerialNumber, "SerialNumber string");
 static char composite_manufacturer[50];
 
 /*-------------------------------------------------------------------------*/
+/**
+ * next_ep_desc() - advance to the next EP descriptor
+ * @t: currect pointer within descriptor array
+ *
+ * Return: next EP descriptor or NULL
+ *
+ * Iterate over @t until either EP descriptor found or
+ * NULL (that indicates end of list) encountered
+ */
+static struct usb_descriptor_header**
+next_ep_desc(struct usb_descriptor_header **t)
+{
+        for (; *t; t++) {
+                if ((*t)->bDescriptorType == USB_DT_ENDPOINT)
+                        return t;
+        }
+        return NULL;
+}
+
+/*
+ * for_each_ep_desc()- iterate over endpoint descriptors in the
+ *              descriptors list
+ * @start:      pointer within descriptor array.
+ * @ep_desc:    endpoint descriptor to use as the loop cursor
+ */
+#define for_each_ep_desc(start, ep_desc) \
+        for (ep_desc = next_ep_desc(start); \
+              ep_desc; ep_desc = next_ep_desc(ep_desc+1))
+
+/**
+ * config_ep_by_speed() - configures the given endpoint
+ * according to gadget speed.
+ * @g: pointer to the gadget
+ * @f: usb function
+ * @_ep: the endpoint to configure
+ *
+ * Return: error code, 0 on success
+ *
+ * This function chooses the right descriptors for a given
+ * endpoint according to gadget speed and saves it in the
+ * endpoint desc field. If the endpoint already has a descriptor
+ * assigned to it - overwrites it with currently corresponding
+ * descriptor. The endpoint maxpacket field is updated according
+ * to the chosen descriptor.
+ * Note: the supplied function should hold all the descriptors
+ * for supported speeds
+ */
+int config_ep_by_speed(struct usb_gadget *g,
+                        struct usb_function *f,
+                        struct usb_ep *_ep)
+{
+        struct usb_endpoint_descriptor *chosen_desc = NULL;
+        struct usb_descriptor_header **speed_desc = NULL;
+
+        struct usb_descriptor_header **d_spd; /* cursor for speed desc */
+
+        if (!g || !f || !_ep)
+                return -EIO;
+
+        /* select desired speed */
+        switch (g->speed) {
+        case USB_SPEED_HIGH:
+                if (gadget_is_dualspeed(g)) {
+                        speed_desc = f->hs_descriptors;
+                        break;
+                }
+                /* else: fall through */
+        default:
+                speed_desc = f->descriptors;
+        }
+        /* find descriptors */
+        for_each_ep_desc(speed_desc, d_spd) {
+                chosen_desc = (struct usb_endpoint_descriptor *)*d_spd;
+                if (chosen_desc->bEndpointAddress == _ep->address)
+                        goto ep_found;
+        }
+        return -EIO;
+
+ep_found:
+        /* commit results */
+        _ep->maxpacket = le16_to_cpu(chosen_desc->wMaxPacketSize);
+        _ep->desc = chosen_desc;
+
+        return 0;
+}
 
 /**
  * usb_add_function() - add a function to a configuration