[PATCH v2] usb: gadget: Fix issue with config_ep_by_speed function.

[Pawel Laszczak]

This patch adds new config_ep_by_speed_and_alt function which
extends the config_ep_by_speed about alt parameter.
This additional parameter allows to find proper usb_ss_ep_comp_descriptor.

Problem has appeared during testing f_tcm (BOT/UAS) driver function.

f_tcm function for SS use array of headers for both  BOT/UAS alternate
setting:

static struct usb_descriptor_header *uasp_ss_function_desc[] = {
        (struct usb_descriptor_header *) &bot_intf_desc,
        (struct usb_descriptor_header *) &uasp_ss_bi_desc,
        (struct usb_descriptor_header *) &bot_bi_ep_comp_desc,
        (struct usb_descriptor_header *) &uasp_ss_bo_desc,
        (struct usb_descriptor_header *) &bot_bo_ep_comp_desc,

        (struct usb_descriptor_header *) &uasp_intf_desc,
        (struct usb_descriptor_header *) &uasp_ss_bi_desc,
        (struct usb_descriptor_header *) &uasp_bi_ep_comp_desc,
        (struct usb_descriptor_header *) &uasp_bi_pipe_desc,
        (struct usb_descriptor_header *) &uasp_ss_bo_desc,
        (struct usb_descriptor_header *) &uasp_bo_ep_comp_desc,
        (struct usb_descriptor_header *) &uasp_bo_pipe_desc,
        (struct usb_descriptor_header *) &uasp_ss_status_desc,
        (struct usb_descriptor_header *) &uasp_status_in_ep_comp_desc,
        (struct usb_descriptor_header *) &uasp_status_pipe_desc,
        (struct usb_descriptor_header *) &uasp_ss_cmd_desc,
        (struct usb_descriptor_header *) &uasp_cmd_comp_desc,
        (struct usb_descriptor_header *) &uasp_cmd_pipe_desc,
        NULL,
};

The first 5 descriptors are associated with BOT alternate setting,
and others are associated with UAS.

During handling UAS alternate setting f_tcm driver invokes
config_ep_by_speed and this function sets incorrect companion endpoint
descriptor in usb_ep object.

Instead setting ep->comp_desc to uasp_bi_ep_comp_desc function in this
case set ep->comp_desc to uasp_ss_bi_desc.

This is due to the fact that it searches endpoint based on endpoint
address:

        for_each_ep_desc(speed_desc, d_spd) {
                chosen_desc = (struct usb_endpoint_descriptor *)*d_spd;
                if (chosen_desc->bEndpoitAddress == _ep->address)
                        goto ep_found;
        }

And in result it uses the descriptor from BOT alternate setting
instead UAS.

Finally, it causes that controller driver during enabling endpoints
detect that just enabled endpoint for bot.

Signed-off-by: Jayshri Pawar <jpawar@xxxxxxxxxxx>
Signed-off-by: Pawel Laszczak <pawell@xxxxxxxxxxx>
---
Changelog:
v2
- redefine config_ep_by_speed() instead removing it.
- remove changes from f_tcm.c file.

 drivers/usb/gadget/composite.c | 78 ++++++++++++++++++++++++++--------
 include/linux/usb/composite.h  |  3 ++
 2 files changed, 64 insertions(+), 17 deletions(-)

diff --git a/drivers/usb/gadget/composite.c b/drivers/usb/gadget/composite.c
index 3b4f67000315..858a71fbcd13 100644
--- a/drivers/usb/gadget/composite.c
+++ b/drivers/usb/gadget/composite.c
@@ -96,40 +96,43 @@ function_descriptors(struct usb_function *f,
 }
 
 /**
- * next_ep_desc() - advance to the next EP descriptor
+ * next_desc() - advance to the next desc_type descriptor
  * @t: currect pointer within descriptor array
+ * @desc_type: descriptor type
  *
- * Return: next EP descriptor or NULL
+ * Return: next desc_type descriptor or NULL
  *
- * Iterate over @t until either EP descriptor found or
+ * Iterate over @t until either desc_type descriptor found or
  * NULL (that indicates end of list) encountered
  */
 static struct usb_descriptor_header**
-next_ep_desc(struct usb_descriptor_header **t)
+next_desc(struct usb_descriptor_header **t, u8 desc_type)
 {
 	for (; *t; t++) {
-		if ((*t)->bDescriptorType == USB_DT_ENDPOINT)
+		if ((*t)->bDescriptorType == desc_type)
 			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
+ * for_each_desc() - iterate over desc_type descriptors in the
+ * descriptors list
+ * @start: pointer within descriptor array.
+ * @iter_desc: desc_type descriptor to use as the loop cursor
+ * @desc_type: wanted descriptr type
  */
-#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))
+#define for_each_desc(start, iter_desc, desc_type) \
+	for (iter_desc = next_desc(start, desc_type); \
+	     iter_desc; iter_desc = next_desc(iter_desc + 1, desc_type))
 
 /**
- * config_ep_by_speed() - configures the given endpoint
+ * config_ep_by_speed_and_alt() - configures the given endpoint
  * according to gadget speed.
  * @g: pointer to the gadget
  * @f: usb function
  * @_ep: the endpoint to configure
+ * @alt: alternate setting number
  *
  * Return: error code, 0 on success
  *
@@ -142,11 +145,13 @@ next_ep_desc(struct usb_descriptor_header **t)
  * 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)
+int config_ep_by_speed_and_alt(struct usb_gadget *g,
+				struct usb_function *f,
+				struct usb_ep *_ep,
+				u8 alt)
 {
 	struct usb_endpoint_descriptor *chosen_desc = NULL;
+	struct usb_interface_descriptor *int_desc = NULL;
 	struct usb_descriptor_header **speed_desc = NULL;
 
 	struct usb_ss_ep_comp_descriptor *comp_desc = NULL;
@@ -182,8 +187,21 @@ int config_ep_by_speed(struct usb_gadget *g,
 	default:
 		speed_desc = f->fs_descriptors;
 	}
+
+	/* find correct alternate setting descriptor */
+	for_each_desc(speed_desc, d_spd, USB_DT_INTERFACE) {
+		int_desc = (struct usb_interface_descriptor *)*d_spd;
+
+		if (int_desc->bAlternateSetting == alt) {
+			speed_desc = d_spd;
+			goto intf_found;
+		}
+	}
+	return -EIO;
+
+intf_found:
 	/* find descriptors */
-	for_each_ep_desc(speed_desc, d_spd) {
+	for_each_desc(speed_desc, d_spd, USB_DT_ENDPOINT) {
 		chosen_desc = (struct usb_endpoint_descriptor *)*d_spd;
 		if (chosen_desc->bEndpointAddress == _ep->address)
 			goto ep_found;
@@ -237,6 +255,32 @@ int config_ep_by_speed(struct usb_gadget *g,
 	}
 	return 0;
 }
+EXPORT_SYMBOL_GPL(config_ep_by_speed_and_alt);
+
+/**
+ * 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)
+{
+	return config_ep_by_speed_and_alt(g, f, _ep, 0);
+}
 EXPORT_SYMBOL_GPL(config_ep_by_speed);
 
 /**
diff --git a/include/linux/usb/composite.h b/include/linux/usb/composite.h
index 8675e145ea8b..2040696d75b6 100644
--- a/include/linux/usb/composite.h
+++ b/include/linux/usb/composite.h
@@ -249,6 +249,9 @@ int usb_function_activate(struct usb_function *);
 
 int usb_interface_id(struct usb_configuration *, struct usb_function *);
 
+int config_ep_by_speed_and_alt(struct usb_gadget *g, struct usb_function *f,
+				struct usb_ep *_ep, u8 alt);
+
 int config_ep_by_speed(struct usb_gadget *g, struct usb_function *f,
 			struct usb_ep *_ep);
 
-- 
2.17.1