greybus: rename es1-ap-usb.ko to gb-es1.ko
authorGreg Kroah-Hartman <greg@kroah.com>
Thu, 15 Jan 2015 01:08:02 +0000 (17:08 -0800)
committerGreg Kroah-Hartman <greg@kroah.com>
Thu, 15 Jan 2015 05:10:31 +0000 (21:10 -0800)
Use the "gb-" prefix for the ES1 Host controller driver.

Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>
Reviewed-by: Alex Elder <elder@linaro.org>
drivers/staging/greybus/Makefile
drivers/staging/greybus/es1-ap-usb.c [deleted file]
drivers/staging/greybus/gb-es1.c [new file with mode: 0644]

index 1734480d8dcdc9dd824923aa7f46771201aee25b..5a7c58deb92abbf6b608b405140cd76484137e15 100644 (file)
@@ -21,7 +21,7 @@ obj-m += greybus.o
 obj-m += gb-phy.o
 obj-m += gb-vibrator.o
 obj-m += gb-battery.o
-obj-m += es1-ap-usb.o
+obj-m += gb-es1.o
 
 KERNELVER              ?= $(shell uname -r)
 KERNELDIR              ?= /lib/modules/$(KERNELVER)/build
diff --git a/drivers/staging/greybus/es1-ap-usb.c b/drivers/staging/greybus/es1-ap-usb.c
deleted file mode 100644 (file)
index 27416e4..0000000
+++ /dev/null
@@ -1,617 +0,0 @@
-/*
- * Greybus "AP" USB driver
- *
- * Copyright 2014 Google Inc.
- * Copyright 2014 Linaro Ltd.
- *
- * Released under the GPLv2 only.
- */
-#include <linux/kernel.h>
-#include <linux/module.h>
-#include <linux/slab.h>
-#include <linux/errno.h>
-#include <linux/sizes.h>
-#include <linux/usb.h>
-
-#include "greybus.h"
-#include "svc_msg.h"
-#include "kernel_ver.h"
-
-/*
- * Macros for making pointers explicitly opaque, such that the result
- * isn't valid but also can't be mistaken for an ERR_PTR() value.
- */
-#define conceal_urb(urb)       ((void *)((uintptr_t)(urb) ^ 0xbad))
-#define reveal_urb(cookie)     ((void *)((uintptr_t)(cookie) ^ 0xbad))
-
-/* Memory sizes for the buffers sent to/from the ES1 controller */
-#define ES1_SVC_MSG_SIZE       (sizeof(struct svc_msg) + SZ_64K)
-#define ES1_GBUF_MSG_SIZE_MAX  PAGE_SIZE
-
-static const struct usb_device_id id_table[] = {
-       /* Made up numbers for the SVC USB Bridge in ES1 */
-       { USB_DEVICE(0xffff, 0x0001) },
-       { },
-};
-MODULE_DEVICE_TABLE(usb, id_table);
-
-/*
- * Number of CPort IN urbs in flight at any point in time.
- * Adjust if we are having stalls in the USB buffer due to not enough urbs in
- * flight.
- */
-#define NUM_CPORT_IN_URB       4
-
-/* Number of CPort OUT urbs in flight at any point in time.
- * Adjust if we get messages saying we are out of urbs in the system log.
- */
-#define NUM_CPORT_OUT_URB      8
-
-/**
- * es1_ap_dev - ES1 USB Bridge to AP structure
- * @usb_dev: pointer to the USB device we are.
- * @usb_intf: pointer to the USB interface we are bound to.
- * @hd: pointer to our greybus_host_device structure
- * @control_endpoint: endpoint to send data to SVC
- * @svc_endpoint: endpoint for SVC data in
- * @cport_in_endpoint: bulk in endpoint for CPort data
- * @cport-out_endpoint: bulk out endpoint for CPort data
- * @svc_buffer: buffer for SVC messages coming in on @svc_endpoint
- * @svc_urb: urb for SVC messages coming in on @svc_endpoint
- * @cport_in_urb: array of urbs for the CPort in messages
- * @cport_in_buffer: array of buffers for the @cport_in_urb urbs
- * @cport_out_urb: array of urbs for the CPort out messages
- * @cport_out_urb_busy: array of flags to see if the @cport_out_urb is busy or
- *                     not.
- * @cport_out_urb_lock: locks the @cport_out_urb_busy "list"
- */
-struct es1_ap_dev {
-       struct usb_device *usb_dev;
-       struct usb_interface *usb_intf;
-       struct greybus_host_device *hd;
-
-       __u8 control_endpoint;
-       __u8 svc_endpoint;
-       __u8 cport_in_endpoint;
-       __u8 cport_out_endpoint;
-
-       u8 *svc_buffer;
-       struct urb *svc_urb;
-
-       struct urb *cport_in_urb[NUM_CPORT_IN_URB];
-       u8 *cport_in_buffer[NUM_CPORT_IN_URB];
-       struct urb *cport_out_urb[NUM_CPORT_OUT_URB];
-       bool cport_out_urb_busy[NUM_CPORT_OUT_URB];
-       spinlock_t cport_out_urb_lock;
-};
-
-static inline struct es1_ap_dev *hd_to_es1(struct greybus_host_device *hd)
-{
-       return (struct es1_ap_dev *)&hd->hd_priv;
-}
-
-static void cport_out_callback(struct urb *urb);
-
-/*
- * Buffer constraints for the host driver.
- *
- * A "buffer" is used to hold data to be transferred for Greybus by
- * the host driver.  A buffer is represented by a "buffer pointer",
- * which defines a region of memory used by the host driver for
- * transferring the data.  When Greybus allocates a buffer, it must
- * do so subject to the constraints associated with the host driver.
- * These constraints are specified by two parameters: the
- * headroom; and the maximum buffer size.
- *
- *                     +------------------+
- *                     |    Host driver   | \
- *                     |   reserved area  |  }- headroom
- *                     |      . . .       | /
- *  buffer pointer ---> +------------------+
- *                     | Buffer space for | \
- *                     | transferred data |  }- buffer size
- *                     |      . . .       | /   (limited to size_max)
- *                     +------------------+
- *
- *  headroom:  Every buffer must have at least this much space
- *             *before* the buffer pointer, reserved for use by the
- *             host driver.  I.e., ((char *)buffer - headroom) must
- *             point to valid memory, usable only by the host driver.
- *  size_max:  The maximum size of a buffer (not including the
- *             headroom) must not exceed this.
- */
-static void hd_buffer_constraints(struct greybus_host_device *hd)
-{
-       /*
-        * Only one byte is required, but this produces a result
-        * that's better aligned for the user.
-        */
-       hd->buffer_headroom = sizeof(u32);      /* For cport id */
-       hd->buffer_size_max = ES1_GBUF_MSG_SIZE_MAX;
-       BUILD_BUG_ON(hd->buffer_headroom > GB_BUFFER_HEADROOM_MAX);
-}
-
-#define ES1_TIMEOUT    500     /* 500 ms for the SVC to do something */
-static int submit_svc(struct svc_msg *svc_msg, struct greybus_host_device *hd)
-{
-       struct es1_ap_dev *es1 = hd_to_es1(hd);
-       int retval;
-
-       /* SVC messages go down our control pipe */
-       retval = usb_control_msg(es1->usb_dev,
-                                usb_sndctrlpipe(es1->usb_dev,
-                                                es1->control_endpoint),
-                                0x01,  /* vendor request AP message */
-                                USB_DIR_OUT | USB_TYPE_VENDOR | USB_RECIP_INTERFACE,
-                                0x00, 0x00,
-                                (char *)svc_msg,
-                                sizeof(*svc_msg),
-                                ES1_TIMEOUT);
-       if (retval != sizeof(*svc_msg))
-               return retval;
-
-       return 0;
-}
-
-static struct urb *next_free_urb(struct es1_ap_dev *es1, gfp_t gfp_mask)
-{
-       struct urb *urb = NULL;
-       unsigned long flags;
-       int i;
-
-       spin_lock_irqsave(&es1->cport_out_urb_lock, flags);
-
-       /* Look in our pool of allocated urbs first, as that's the "fastest" */
-       for (i = 0; i < NUM_CPORT_OUT_URB; ++i) {
-               if (es1->cport_out_urb_busy[i] == false) {
-                       es1->cport_out_urb_busy[i] = true;
-                       urb = es1->cport_out_urb[i];
-                       break;
-               }
-       }
-       spin_unlock_irqrestore(&es1->cport_out_urb_lock, flags);
-       if (urb)
-               return urb;
-
-       /*
-        * Crap, pool is empty, complain to the syslog and go allocate one
-        * dynamically as we have to succeed.
-        */
-       dev_err(&es1->usb_dev->dev,
-               "No free CPort OUT urbs, having to dynamically allocate one!\n");
-       urb = usb_alloc_urb(0, gfp_mask);
-       if (!urb)
-               return NULL;
-
-       return urb;
-}
-
-/*
- * Returns an opaque cookie value if successful, or a pointer coded
- * error otherwise.  If the caller wishes to cancel the in-flight
- * buffer, it must supply the returned cookie to the cancel routine.
- */
-static void *buffer_send(struct greybus_host_device *hd, u16 cport_id,
-                       void *buffer, size_t buffer_size, gfp_t gfp_mask)
-{
-       struct es1_ap_dev *es1 = hd_to_es1(hd);
-       struct usb_device *udev = es1->usb_dev;
-       u8 *transfer_buffer = buffer;
-       int transfer_buffer_size;
-       int retval;
-       struct urb *urb;
-
-       if (!buffer) {
-               pr_err("null buffer supplied to send\n");
-               return ERR_PTR(-EINVAL);
-       }
-       if (buffer_size > (size_t)INT_MAX) {
-               pr_err("bad buffer size (%zu) supplied to send\n", buffer_size);
-               return ERR_PTR(-EINVAL);
-       }
-       transfer_buffer--;
-       transfer_buffer_size = buffer_size + 1;
-
-       /*
-        * The data actually transferred will include an indication
-        * of where the data should be sent.  Do one last check of
-        * the target CPort id before filling it in.
-        */
-       if (cport_id == CPORT_ID_BAD) {
-               pr_err("request to send inbound data buffer\n");
-               return ERR_PTR(-EINVAL);
-       }
-       if (cport_id > (u16)U8_MAX) {
-               pr_err("cport_id (%hd) is out of range for ES1\n", cport_id);
-               return ERR_PTR(-EINVAL);
-       }
-       /* OK, the destination is fine; record it in the transfer buffer */
-       *transfer_buffer = cport_id;
-
-       /* Find a free urb */
-       urb = next_free_urb(es1, gfp_mask);
-       if (!urb)
-               return ERR_PTR(-ENOMEM);
-
-       usb_fill_bulk_urb(urb, udev,
-                         usb_sndbulkpipe(udev, es1->cport_out_endpoint),
-                         transfer_buffer, transfer_buffer_size,
-                         cport_out_callback, hd);
-       retval = usb_submit_urb(urb, gfp_mask);
-       if (retval) {
-               pr_err("error %d submitting URB\n", retval);
-               return ERR_PTR(retval);
-       }
-
-       return conceal_urb(urb);
-}
-
-/*
- * The cookie value supplied is the value that buffer_send()
- * returned to its caller.  It identifies the buffer that should be
- * canceled.  This function must also handle (which is to say,
- * ignore) a null cookie value.
- */
-static void buffer_cancel(void *cookie)
-{
-
-       /*
-        * We really should be defensive and track all outstanding
-        * (sent) buffers rather than trusting the cookie provided
-        * is valid.  For the time being, this will do.
-        */
-       if (cookie)
-               usb_kill_urb(reveal_urb(cookie));
-}
-
-static struct greybus_host_driver es1_driver = {
-       .hd_priv_size           = sizeof(struct es1_ap_dev),
-       .buffer_send            = buffer_send,
-       .buffer_cancel          = buffer_cancel,
-       .submit_svc             = submit_svc,
-};
-
-/* Common function to report consistent warnings based on URB status */
-static int check_urb_status(struct urb *urb)
-{
-       struct device *dev = &urb->dev->dev;
-       int status = urb->status;
-
-       switch (status) {
-       case 0:
-               return 0;
-
-       case -EOVERFLOW:
-               dev_err(dev, "%s: overflow actual length is %d\n",
-                       __func__, urb->actual_length);
-       case -ECONNRESET:
-       case -ENOENT:
-       case -ESHUTDOWN:
-       case -EILSEQ:
-       case -EPROTO:
-               /* device is gone, stop sending */
-               return status;
-       }
-       dev_err(dev, "%s: unknown status %d\n", __func__, status);
-
-       return -EAGAIN;
-}
-
-static void ap_disconnect(struct usb_interface *interface)
-{
-       struct es1_ap_dev *es1;
-       struct usb_device *udev;
-       int i;
-
-       es1 = usb_get_intfdata(interface);
-       if (!es1)
-               return;
-
-       /* Tear down everything! */
-       for (i = 0; i < NUM_CPORT_OUT_URB; ++i) {
-               struct urb *urb = es1->cport_out_urb[i];
-
-               if (!urb)
-                       break;
-               usb_kill_urb(urb);
-               usb_free_urb(urb);
-               es1->cport_out_urb[i] = NULL;
-               es1->cport_out_urb_busy[i] = false;     /* just to be anal */
-       }
-
-       for (i = 0; i < NUM_CPORT_IN_URB; ++i) {
-               struct urb *urb = es1->cport_in_urb[i];
-
-               if (!urb)
-                       break;
-               usb_kill_urb(urb);
-               usb_free_urb(urb);
-               kfree(es1->cport_in_buffer[i]);
-               es1->cport_in_buffer[i] = NULL;
-       }
-
-       usb_kill_urb(es1->svc_urb);
-       usb_free_urb(es1->svc_urb);
-       es1->svc_urb = NULL;
-       kfree(es1->svc_buffer);
-       es1->svc_buffer = NULL;
-
-       usb_set_intfdata(interface, NULL);
-       udev = es1->usb_dev;
-       greybus_remove_hd(es1->hd);
-
-       usb_put_dev(udev);
-}
-
-/* Callback for when we get a SVC message */
-static void svc_in_callback(struct urb *urb)
-{
-       struct greybus_host_device *hd = urb->context;
-       struct device *dev = &urb->dev->dev;
-       int status = check_urb_status(urb);
-       int retval;
-
-       if (status) {
-               if ((status == -EAGAIN) || (status == -EPROTO))
-                       goto exit;
-               dev_err(dev, "urb svc in error %d (dropped)\n", status);
-               return;
-       }
-
-       /* We have a message, create a new message structure, add it to the
-        * list, and wake up our thread that will process the messages.
-        */
-       greybus_svc_in(hd, urb->transfer_buffer, urb->actual_length);
-
-exit:
-       /* resubmit the urb to get more messages */
-       retval = usb_submit_urb(urb, GFP_ATOMIC);
-       if (retval)
-               dev_err(dev, "Can not submit urb for AP data: %d\n", retval);
-}
-
-static void cport_in_callback(struct urb *urb)
-{
-       struct greybus_host_device *hd = urb->context;
-       struct device *dev = &urb->dev->dev;
-       int status = check_urb_status(urb);
-       int retval;
-       u16 cport_id;
-       u8 *data;
-
-       if (status) {
-               if ((status == -EAGAIN) || (status == -EPROTO))
-                       goto exit;
-               dev_err(dev, "urb cport in error %d (dropped)\n", status);
-               return;
-       }
-
-       /* The size has to be at least one, for the cport id */
-       if (!urb->actual_length) {
-               dev_err(dev, "%s: no cport id in input buffer?\n", __func__);
-               goto exit;
-       }
-
-       /*
-        * Our CPort number is the first byte of the data stream,
-        * the rest of the stream is "real" data
-        */
-       data = urb->transfer_buffer;
-       cport_id = (u16)data[0];
-       data = &data[1];
-
-       /* Pass this data to the greybus core */
-       greybus_data_rcvd(hd, cport_id, data, urb->actual_length - 1);
-
-exit:
-       /* put our urb back in the request pool */
-       retval = usb_submit_urb(urb, GFP_ATOMIC);
-       if (retval)
-               dev_err(dev, "%s: error %d in submitting urb.\n",
-                       __func__, retval);
-}
-
-static void cport_out_callback(struct urb *urb)
-{
-       struct greybus_host_device *hd = urb->context;
-       struct es1_ap_dev *es1 = hd_to_es1(hd);
-       unsigned long flags;
-       int status = check_urb_status(urb);
-       u8 *data = urb->transfer_buffer + 1;
-       int i;
-
-       /*
-        * Tell the submitter that the buffer send (attempt) is
-        * complete, and report the status.  The submitter's buffer
-        * starts after the one-byte CPort id we inserted.
-        */
-       data = urb->transfer_buffer + 1;
-       greybus_data_sent(hd, data, status);
-
-       /*
-        * See if this was an urb in our pool, if so mark it "free", otherwise
-        * we need to free it ourselves.
-        */
-       spin_lock_irqsave(&es1->cport_out_urb_lock, flags);
-       for (i = 0; i < NUM_CPORT_OUT_URB; ++i) {
-               if (urb == es1->cport_out_urb[i]) {
-                       es1->cport_out_urb_busy[i] = false;
-                       urb = NULL;
-                       break;
-               }
-       }
-       spin_unlock_irqrestore(&es1->cport_out_urb_lock, flags);
-
-       /* If urb is not NULL, then we need to free this urb */
-       usb_free_urb(urb);
-
-       /*
-        * Rest assured Greg, this craziness is getting fixed.
-        *
-        * Yes, you are right, we aren't telling anyone that the urb finished.
-        * "That's crazy!  How does this all even work?" you might be saying.
-        * The "magic" is the idea that greybus works on the "operation" level,
-        * not the "send a buffer" level.  All operations are "round-trip" with
-        * a response from the device that the operation finished, or it will
-        * time out.  Because of that, we don't care that this urb finished, or
-        * failed, or did anything else, as higher levels of the protocol stack
-        * will handle completions and timeouts and the rest.
-        *
-        * This protocol is "needed" due to some hardware restrictions on the
-        * current generation of Unipro controllers.  Think about it for a
-        * minute, this is a USB driver, talking to a Unipro bridge, impedance
-        * mismatch is huge, yet the Unipro controller are even more
-        * underpowered than this little USB controller.  We rely on the round
-        * trip to keep stalls in the Unipro controllers from happening so that
-        * we can keep data flowing properly, no matter how slow it might be.
-        *
-        * Once again, a wonderful bus protocol cut down in its prime by a naive
-        * controller chip.  We dream of the day we have a "real" HCD for
-        * Unipro.  Until then, we suck it up and make the hardware work, as
-        * that's the job of the firmware and kernel.
-        * </rant>
-        */
-}
-
-/*
- * The ES1 USB Bridge device contains 4 endpoints
- * 1 Control - usual USB stuff + AP -> SVC messages
- * 1 Interrupt IN - SVC -> AP messages
- * 1 Bulk IN - CPort data in
- * 1 Bulk OUT - CPort data out
- */
-static int ap_probe(struct usb_interface *interface,
-                   const struct usb_device_id *id)
-{
-       struct es1_ap_dev *es1;
-       struct greybus_host_device *hd;
-       struct usb_device *udev;
-       struct usb_host_interface *iface_desc;
-       struct usb_endpoint_descriptor *endpoint;
-       bool int_in_found = false;
-       bool bulk_in_found = false;
-       bool bulk_out_found = false;
-       int retval = -ENOMEM;
-       int i;
-       u8 svc_interval = 0;
-
-       udev = usb_get_dev(interface_to_usbdev(interface));
-
-       hd = greybus_create_hd(&es1_driver, &udev->dev);
-       if (!hd) {
-               usb_put_dev(udev);
-               return -ENOMEM;
-       }
-
-       /* Fill in the buffer allocation constraints */
-       hd_buffer_constraints(hd);
-
-       es1 = hd_to_es1(hd);
-       es1->hd = hd;
-       es1->usb_intf = interface;
-       es1->usb_dev = udev;
-       spin_lock_init(&es1->cport_out_urb_lock);
-       usb_set_intfdata(interface, es1);
-
-       /* Control endpoint is the pipe to talk to this AP, so save it off */
-       endpoint = &udev->ep0.desc;
-       es1->control_endpoint = endpoint->bEndpointAddress;
-
-       /* find all 3 of our endpoints */
-       iface_desc = interface->cur_altsetting;
-       for (i = 0; i < iface_desc->desc.bNumEndpoints; ++i) {
-               endpoint = &iface_desc->endpoint[i].desc;
-
-               if (usb_endpoint_is_int_in(endpoint)) {
-                       es1->svc_endpoint = endpoint->bEndpointAddress;
-                       svc_interval = endpoint->bInterval;
-                       int_in_found = true;
-               } else if (usb_endpoint_is_bulk_in(endpoint)) {
-                       es1->cport_in_endpoint = endpoint->bEndpointAddress;
-                       bulk_in_found = true;
-               } else if (usb_endpoint_is_bulk_out(endpoint)) {
-                       es1->cport_out_endpoint = endpoint->bEndpointAddress;
-                       bulk_out_found = true;
-               } else {
-                       dev_err(&udev->dev,
-                               "Unknown endpoint type found, address %x\n",
-                               endpoint->bEndpointAddress);
-               }
-       }
-       if ((int_in_found == false) ||
-           (bulk_in_found == false) ||
-           (bulk_out_found == false)) {
-               dev_err(&udev->dev, "Not enough endpoints found in device, aborting!\n");
-               goto error;
-       }
-
-       /* Create our buffer and URB to get SVC messages, and start it up */
-       es1->svc_buffer = kmalloc(ES1_SVC_MSG_SIZE, GFP_KERNEL);
-       if (!es1->svc_buffer)
-               goto error;
-
-       es1->svc_urb = usb_alloc_urb(0, GFP_KERNEL);
-       if (!es1->svc_urb)
-               goto error;
-
-       usb_fill_int_urb(es1->svc_urb, udev,
-                        usb_rcvintpipe(udev, es1->svc_endpoint),
-                        es1->svc_buffer, ES1_SVC_MSG_SIZE, svc_in_callback,
-                        hd, svc_interval);
-       retval = usb_submit_urb(es1->svc_urb, GFP_KERNEL);
-       if (retval)
-               goto error;
-
-       /* Allocate buffers for our cport in messages and start them up */
-       for (i = 0; i < NUM_CPORT_IN_URB; ++i) {
-               struct urb *urb;
-               u8 *buffer;
-
-               urb = usb_alloc_urb(0, GFP_KERNEL);
-               if (!urb)
-                       goto error;
-               buffer = kmalloc(ES1_GBUF_MSG_SIZE_MAX, GFP_KERNEL);
-               if (!buffer)
-                       goto error;
-
-               usb_fill_bulk_urb(urb, udev,
-                                 usb_rcvbulkpipe(udev, es1->cport_in_endpoint),
-                                 buffer, ES1_GBUF_MSG_SIZE_MAX,
-                                 cport_in_callback, hd);
-               es1->cport_in_urb[i] = urb;
-               es1->cport_in_buffer[i] = buffer;
-               retval = usb_submit_urb(urb, GFP_KERNEL);
-               if (retval)
-                       goto error;
-       }
-
-       /* Allocate urbs for our CPort OUT messages */
-       for (i = 0; i < NUM_CPORT_OUT_URB; ++i) {
-               struct urb *urb;
-
-               urb = usb_alloc_urb(0, GFP_KERNEL);
-               if (!urb)
-                       goto error;
-
-               es1->cport_out_urb[i] = urb;
-               es1->cport_out_urb_busy[i] = false;     /* just to be anal */
-       }
-
-       return 0;
-error:
-       ap_disconnect(interface);
-
-       return retval;
-}
-
-static struct usb_driver es1_ap_driver = {
-       .name =         "es1_ap_driver",
-       .probe =        ap_probe,
-       .disconnect =   ap_disconnect,
-       .id_table =     id_table,
-};
-
-module_usb_driver(es1_ap_driver);
-
-MODULE_LICENSE("GPL");
-MODULE_AUTHOR("Greg Kroah-Hartman <gregkh@linuxfoundation.org>");
diff --git a/drivers/staging/greybus/gb-es1.c b/drivers/staging/greybus/gb-es1.c
new file mode 100644 (file)
index 0000000..27416e4
--- /dev/null
@@ -0,0 +1,617 @@
+/*
+ * Greybus "AP" USB driver
+ *
+ * Copyright 2014 Google Inc.
+ * Copyright 2014 Linaro Ltd.
+ *
+ * Released under the GPLv2 only.
+ */
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/errno.h>
+#include <linux/sizes.h>
+#include <linux/usb.h>
+
+#include "greybus.h"
+#include "svc_msg.h"
+#include "kernel_ver.h"
+
+/*
+ * Macros for making pointers explicitly opaque, such that the result
+ * isn't valid but also can't be mistaken for an ERR_PTR() value.
+ */
+#define conceal_urb(urb)       ((void *)((uintptr_t)(urb) ^ 0xbad))
+#define reveal_urb(cookie)     ((void *)((uintptr_t)(cookie) ^ 0xbad))
+
+/* Memory sizes for the buffers sent to/from the ES1 controller */
+#define ES1_SVC_MSG_SIZE       (sizeof(struct svc_msg) + SZ_64K)
+#define ES1_GBUF_MSG_SIZE_MAX  PAGE_SIZE
+
+static const struct usb_device_id id_table[] = {
+       /* Made up numbers for the SVC USB Bridge in ES1 */
+       { USB_DEVICE(0xffff, 0x0001) },
+       { },
+};
+MODULE_DEVICE_TABLE(usb, id_table);
+
+/*
+ * Number of CPort IN urbs in flight at any point in time.
+ * Adjust if we are having stalls in the USB buffer due to not enough urbs in
+ * flight.
+ */
+#define NUM_CPORT_IN_URB       4
+
+/* Number of CPort OUT urbs in flight at any point in time.
+ * Adjust if we get messages saying we are out of urbs in the system log.
+ */
+#define NUM_CPORT_OUT_URB      8
+
+/**
+ * es1_ap_dev - ES1 USB Bridge to AP structure
+ * @usb_dev: pointer to the USB device we are.
+ * @usb_intf: pointer to the USB interface we are bound to.
+ * @hd: pointer to our greybus_host_device structure
+ * @control_endpoint: endpoint to send data to SVC
+ * @svc_endpoint: endpoint for SVC data in
+ * @cport_in_endpoint: bulk in endpoint for CPort data
+ * @cport-out_endpoint: bulk out endpoint for CPort data
+ * @svc_buffer: buffer for SVC messages coming in on @svc_endpoint
+ * @svc_urb: urb for SVC messages coming in on @svc_endpoint
+ * @cport_in_urb: array of urbs for the CPort in messages
+ * @cport_in_buffer: array of buffers for the @cport_in_urb urbs
+ * @cport_out_urb: array of urbs for the CPort out messages
+ * @cport_out_urb_busy: array of flags to see if the @cport_out_urb is busy or
+ *                     not.
+ * @cport_out_urb_lock: locks the @cport_out_urb_busy "list"
+ */
+struct es1_ap_dev {
+       struct usb_device *usb_dev;
+       struct usb_interface *usb_intf;
+       struct greybus_host_device *hd;
+
+       __u8 control_endpoint;
+       __u8 svc_endpoint;
+       __u8 cport_in_endpoint;
+       __u8 cport_out_endpoint;
+
+       u8 *svc_buffer;
+       struct urb *svc_urb;
+
+       struct urb *cport_in_urb[NUM_CPORT_IN_URB];
+       u8 *cport_in_buffer[NUM_CPORT_IN_URB];
+       struct urb *cport_out_urb[NUM_CPORT_OUT_URB];
+       bool cport_out_urb_busy[NUM_CPORT_OUT_URB];
+       spinlock_t cport_out_urb_lock;
+};
+
+static inline struct es1_ap_dev *hd_to_es1(struct greybus_host_device *hd)
+{
+       return (struct es1_ap_dev *)&hd->hd_priv;
+}
+
+static void cport_out_callback(struct urb *urb);
+
+/*
+ * Buffer constraints for the host driver.
+ *
+ * A "buffer" is used to hold data to be transferred for Greybus by
+ * the host driver.  A buffer is represented by a "buffer pointer",
+ * which defines a region of memory used by the host driver for
+ * transferring the data.  When Greybus allocates a buffer, it must
+ * do so subject to the constraints associated with the host driver.
+ * These constraints are specified by two parameters: the
+ * headroom; and the maximum buffer size.
+ *
+ *                     +------------------+
+ *                     |    Host driver   | \
+ *                     |   reserved area  |  }- headroom
+ *                     |      . . .       | /
+ *  buffer pointer ---> +------------------+
+ *                     | Buffer space for | \
+ *                     | transferred data |  }- buffer size
+ *                     |      . . .       | /   (limited to size_max)
+ *                     +------------------+
+ *
+ *  headroom:  Every buffer must have at least this much space
+ *             *before* the buffer pointer, reserved for use by the
+ *             host driver.  I.e., ((char *)buffer - headroom) must
+ *             point to valid memory, usable only by the host driver.
+ *  size_max:  The maximum size of a buffer (not including the
+ *             headroom) must not exceed this.
+ */
+static void hd_buffer_constraints(struct greybus_host_device *hd)
+{
+       /*
+        * Only one byte is required, but this produces a result
+        * that's better aligned for the user.
+        */
+       hd->buffer_headroom = sizeof(u32);      /* For cport id */
+       hd->buffer_size_max = ES1_GBUF_MSG_SIZE_MAX;
+       BUILD_BUG_ON(hd->buffer_headroom > GB_BUFFER_HEADROOM_MAX);
+}
+
+#define ES1_TIMEOUT    500     /* 500 ms for the SVC to do something */
+static int submit_svc(struct svc_msg *svc_msg, struct greybus_host_device *hd)
+{
+       struct es1_ap_dev *es1 = hd_to_es1(hd);
+       int retval;
+
+       /* SVC messages go down our control pipe */
+       retval = usb_control_msg(es1->usb_dev,
+                                usb_sndctrlpipe(es1->usb_dev,
+                                                es1->control_endpoint),
+                                0x01,  /* vendor request AP message */
+                                USB_DIR_OUT | USB_TYPE_VENDOR | USB_RECIP_INTERFACE,
+                                0x00, 0x00,
+                                (char *)svc_msg,
+                                sizeof(*svc_msg),
+                                ES1_TIMEOUT);
+       if (retval != sizeof(*svc_msg))
+               return retval;
+
+       return 0;
+}
+
+static struct urb *next_free_urb(struct es1_ap_dev *es1, gfp_t gfp_mask)
+{
+       struct urb *urb = NULL;
+       unsigned long flags;
+       int i;
+
+       spin_lock_irqsave(&es1->cport_out_urb_lock, flags);
+
+       /* Look in our pool of allocated urbs first, as that's the "fastest" */
+       for (i = 0; i < NUM_CPORT_OUT_URB; ++i) {
+               if (es1->cport_out_urb_busy[i] == false) {
+                       es1->cport_out_urb_busy[i] = true;
+                       urb = es1->cport_out_urb[i];
+                       break;
+               }
+       }
+       spin_unlock_irqrestore(&es1->cport_out_urb_lock, flags);
+       if (urb)
+               return urb;
+
+       /*
+        * Crap, pool is empty, complain to the syslog and go allocate one
+        * dynamically as we have to succeed.
+        */
+       dev_err(&es1->usb_dev->dev,
+               "No free CPort OUT urbs, having to dynamically allocate one!\n");
+       urb = usb_alloc_urb(0, gfp_mask);
+       if (!urb)
+               return NULL;
+
+       return urb;
+}
+
+/*
+ * Returns an opaque cookie value if successful, or a pointer coded
+ * error otherwise.  If the caller wishes to cancel the in-flight
+ * buffer, it must supply the returned cookie to the cancel routine.
+ */
+static void *buffer_send(struct greybus_host_device *hd, u16 cport_id,
+                       void *buffer, size_t buffer_size, gfp_t gfp_mask)
+{
+       struct es1_ap_dev *es1 = hd_to_es1(hd);
+       struct usb_device *udev = es1->usb_dev;
+       u8 *transfer_buffer = buffer;
+       int transfer_buffer_size;
+       int retval;
+       struct urb *urb;
+
+       if (!buffer) {
+               pr_err("null buffer supplied to send\n");
+               return ERR_PTR(-EINVAL);
+       }
+       if (buffer_size > (size_t)INT_MAX) {
+               pr_err("bad buffer size (%zu) supplied to send\n", buffer_size);
+               return ERR_PTR(-EINVAL);
+       }
+       transfer_buffer--;
+       transfer_buffer_size = buffer_size + 1;
+
+       /*
+        * The data actually transferred will include an indication
+        * of where the data should be sent.  Do one last check of
+        * the target CPort id before filling it in.
+        */
+       if (cport_id == CPORT_ID_BAD) {
+               pr_err("request to send inbound data buffer\n");
+               return ERR_PTR(-EINVAL);
+       }
+       if (cport_id > (u16)U8_MAX) {
+               pr_err("cport_id (%hd) is out of range for ES1\n", cport_id);
+               return ERR_PTR(-EINVAL);
+       }
+       /* OK, the destination is fine; record it in the transfer buffer */
+       *transfer_buffer = cport_id;
+
+       /* Find a free urb */
+       urb = next_free_urb(es1, gfp_mask);
+       if (!urb)
+               return ERR_PTR(-ENOMEM);
+
+       usb_fill_bulk_urb(urb, udev,
+                         usb_sndbulkpipe(udev, es1->cport_out_endpoint),
+                         transfer_buffer, transfer_buffer_size,
+                         cport_out_callback, hd);
+       retval = usb_submit_urb(urb, gfp_mask);
+       if (retval) {
+               pr_err("error %d submitting URB\n", retval);
+               return ERR_PTR(retval);
+       }
+
+       return conceal_urb(urb);
+}
+
+/*
+ * The cookie value supplied is the value that buffer_send()
+ * returned to its caller.  It identifies the buffer that should be
+ * canceled.  This function must also handle (which is to say,
+ * ignore) a null cookie value.
+ */
+static void buffer_cancel(void *cookie)
+{
+
+       /*
+        * We really should be defensive and track all outstanding
+        * (sent) buffers rather than trusting the cookie provided
+        * is valid.  For the time being, this will do.
+        */
+       if (cookie)
+               usb_kill_urb(reveal_urb(cookie));
+}
+
+static struct greybus_host_driver es1_driver = {
+       .hd_priv_size           = sizeof(struct es1_ap_dev),
+       .buffer_send            = buffer_send,
+       .buffer_cancel          = buffer_cancel,
+       .submit_svc             = submit_svc,
+};
+
+/* Common function to report consistent warnings based on URB status */
+static int check_urb_status(struct urb *urb)
+{
+       struct device *dev = &urb->dev->dev;
+       int status = urb->status;
+
+       switch (status) {
+       case 0:
+               return 0;
+
+       case -EOVERFLOW:
+               dev_err(dev, "%s: overflow actual length is %d\n",
+                       __func__, urb->actual_length);
+       case -ECONNRESET:
+       case -ENOENT:
+       case -ESHUTDOWN:
+       case -EILSEQ:
+       case -EPROTO:
+               /* device is gone, stop sending */
+               return status;
+       }
+       dev_err(dev, "%s: unknown status %d\n", __func__, status);
+
+       return -EAGAIN;
+}
+
+static void ap_disconnect(struct usb_interface *interface)
+{
+       struct es1_ap_dev *es1;
+       struct usb_device *udev;
+       int i;
+
+       es1 = usb_get_intfdata(interface);
+       if (!es1)
+               return;
+
+       /* Tear down everything! */
+       for (i = 0; i < NUM_CPORT_OUT_URB; ++i) {
+               struct urb *urb = es1->cport_out_urb[i];
+
+               if (!urb)
+                       break;
+               usb_kill_urb(urb);
+               usb_free_urb(urb);
+               es1->cport_out_urb[i] = NULL;
+               es1->cport_out_urb_busy[i] = false;     /* just to be anal */
+       }
+
+       for (i = 0; i < NUM_CPORT_IN_URB; ++i) {
+               struct urb *urb = es1->cport_in_urb[i];
+
+               if (!urb)
+                       break;
+               usb_kill_urb(urb);
+               usb_free_urb(urb);
+               kfree(es1->cport_in_buffer[i]);
+               es1->cport_in_buffer[i] = NULL;
+       }
+
+       usb_kill_urb(es1->svc_urb);
+       usb_free_urb(es1->svc_urb);
+       es1->svc_urb = NULL;
+       kfree(es1->svc_buffer);
+       es1->svc_buffer = NULL;
+
+       usb_set_intfdata(interface, NULL);
+       udev = es1->usb_dev;
+       greybus_remove_hd(es1->hd);
+
+       usb_put_dev(udev);
+}
+
+/* Callback for when we get a SVC message */
+static void svc_in_callback(struct urb *urb)
+{
+       struct greybus_host_device *hd = urb->context;
+       struct device *dev = &urb->dev->dev;
+       int status = check_urb_status(urb);
+       int retval;
+
+       if (status) {
+               if ((status == -EAGAIN) || (status == -EPROTO))
+                       goto exit;
+               dev_err(dev, "urb svc in error %d (dropped)\n", status);
+               return;
+       }
+
+       /* We have a message, create a new message structure, add it to the
+        * list, and wake up our thread that will process the messages.
+        */
+       greybus_svc_in(hd, urb->transfer_buffer, urb->actual_length);
+
+exit:
+       /* resubmit the urb to get more messages */
+       retval = usb_submit_urb(urb, GFP_ATOMIC);
+       if (retval)
+               dev_err(dev, "Can not submit urb for AP data: %d\n", retval);
+}
+
+static void cport_in_callback(struct urb *urb)
+{
+       struct greybus_host_device *hd = urb->context;
+       struct device *dev = &urb->dev->dev;
+       int status = check_urb_status(urb);
+       int retval;
+       u16 cport_id;
+       u8 *data;
+
+       if (status) {
+               if ((status == -EAGAIN) || (status == -EPROTO))
+                       goto exit;
+               dev_err(dev, "urb cport in error %d (dropped)\n", status);
+               return;
+       }
+
+       /* The size has to be at least one, for the cport id */
+       if (!urb->actual_length) {
+               dev_err(dev, "%s: no cport id in input buffer?\n", __func__);
+               goto exit;
+       }
+
+       /*
+        * Our CPort number is the first byte of the data stream,
+        * the rest of the stream is "real" data
+        */
+       data = urb->transfer_buffer;
+       cport_id = (u16)data[0];
+       data = &data[1];
+
+       /* Pass this data to the greybus core */
+       greybus_data_rcvd(hd, cport_id, data, urb->actual_length - 1);
+
+exit:
+       /* put our urb back in the request pool */
+       retval = usb_submit_urb(urb, GFP_ATOMIC);
+       if (retval)
+               dev_err(dev, "%s: error %d in submitting urb.\n",
+                       __func__, retval);
+}
+
+static void cport_out_callback(struct urb *urb)
+{
+       struct greybus_host_device *hd = urb->context;
+       struct es1_ap_dev *es1 = hd_to_es1(hd);
+       unsigned long flags;
+       int status = check_urb_status(urb);
+       u8 *data = urb->transfer_buffer + 1;
+       int i;
+
+       /*
+        * Tell the submitter that the buffer send (attempt) is
+        * complete, and report the status.  The submitter's buffer
+        * starts after the one-byte CPort id we inserted.
+        */
+       data = urb->transfer_buffer + 1;
+       greybus_data_sent(hd, data, status);
+
+       /*
+        * See if this was an urb in our pool, if so mark it "free", otherwise
+        * we need to free it ourselves.
+        */
+       spin_lock_irqsave(&es1->cport_out_urb_lock, flags);
+       for (i = 0; i < NUM_CPORT_OUT_URB; ++i) {
+               if (urb == es1->cport_out_urb[i]) {
+                       es1->cport_out_urb_busy[i] = false;
+                       urb = NULL;
+                       break;
+               }
+       }
+       spin_unlock_irqrestore(&es1->cport_out_urb_lock, flags);
+
+       /* If urb is not NULL, then we need to free this urb */
+       usb_free_urb(urb);
+
+       /*
+        * Rest assured Greg, this craziness is getting fixed.
+        *
+        * Yes, you are right, we aren't telling anyone that the urb finished.
+        * "That's crazy!  How does this all even work?" you might be saying.
+        * The "magic" is the idea that greybus works on the "operation" level,
+        * not the "send a buffer" level.  All operations are "round-trip" with
+        * a response from the device that the operation finished, or it will
+        * time out.  Because of that, we don't care that this urb finished, or
+        * failed, or did anything else, as higher levels of the protocol stack
+        * will handle completions and timeouts and the rest.
+        *
+        * This protocol is "needed" due to some hardware restrictions on the
+        * current generation of Unipro controllers.  Think about it for a
+        * minute, this is a USB driver, talking to a Unipro bridge, impedance
+        * mismatch is huge, yet the Unipro controller are even more
+        * underpowered than this little USB controller.  We rely on the round
+        * trip to keep stalls in the Unipro controllers from happening so that
+        * we can keep data flowing properly, no matter how slow it might be.
+        *
+        * Once again, a wonderful bus protocol cut down in its prime by a naive
+        * controller chip.  We dream of the day we have a "real" HCD for
+        * Unipro.  Until then, we suck it up and make the hardware work, as
+        * that's the job of the firmware and kernel.
+        * </rant>
+        */
+}
+
+/*
+ * The ES1 USB Bridge device contains 4 endpoints
+ * 1 Control - usual USB stuff + AP -> SVC messages
+ * 1 Interrupt IN - SVC -> AP messages
+ * 1 Bulk IN - CPort data in
+ * 1 Bulk OUT - CPort data out
+ */
+static int ap_probe(struct usb_interface *interface,
+                   const struct usb_device_id *id)
+{
+       struct es1_ap_dev *es1;
+       struct greybus_host_device *hd;
+       struct usb_device *udev;
+       struct usb_host_interface *iface_desc;
+       struct usb_endpoint_descriptor *endpoint;
+       bool int_in_found = false;
+       bool bulk_in_found = false;
+       bool bulk_out_found = false;
+       int retval = -ENOMEM;
+       int i;
+       u8 svc_interval = 0;
+
+       udev = usb_get_dev(interface_to_usbdev(interface));
+
+       hd = greybus_create_hd(&es1_driver, &udev->dev);
+       if (!hd) {
+               usb_put_dev(udev);
+               return -ENOMEM;
+       }
+
+       /* Fill in the buffer allocation constraints */
+       hd_buffer_constraints(hd);
+
+       es1 = hd_to_es1(hd);
+       es1->hd = hd;
+       es1->usb_intf = interface;
+       es1->usb_dev = udev;
+       spin_lock_init(&es1->cport_out_urb_lock);
+       usb_set_intfdata(interface, es1);
+
+       /* Control endpoint is the pipe to talk to this AP, so save it off */
+       endpoint = &udev->ep0.desc;
+       es1->control_endpoint = endpoint->bEndpointAddress;
+
+       /* find all 3 of our endpoints */
+       iface_desc = interface->cur_altsetting;
+       for (i = 0; i < iface_desc->desc.bNumEndpoints; ++i) {
+               endpoint = &iface_desc->endpoint[i].desc;
+
+               if (usb_endpoint_is_int_in(endpoint)) {
+                       es1->svc_endpoint = endpoint->bEndpointAddress;
+                       svc_interval = endpoint->bInterval;
+                       int_in_found = true;
+               } else if (usb_endpoint_is_bulk_in(endpoint)) {
+                       es1->cport_in_endpoint = endpoint->bEndpointAddress;
+                       bulk_in_found = true;
+               } else if (usb_endpoint_is_bulk_out(endpoint)) {
+                       es1->cport_out_endpoint = endpoint->bEndpointAddress;
+                       bulk_out_found = true;
+               } else {
+                       dev_err(&udev->dev,
+                               "Unknown endpoint type found, address %x\n",
+                               endpoint->bEndpointAddress);
+               }
+       }
+       if ((int_in_found == false) ||
+           (bulk_in_found == false) ||
+           (bulk_out_found == false)) {
+               dev_err(&udev->dev, "Not enough endpoints found in device, aborting!\n");
+               goto error;
+       }
+
+       /* Create our buffer and URB to get SVC messages, and start it up */
+       es1->svc_buffer = kmalloc(ES1_SVC_MSG_SIZE, GFP_KERNEL);
+       if (!es1->svc_buffer)
+               goto error;
+
+       es1->svc_urb = usb_alloc_urb(0, GFP_KERNEL);
+       if (!es1->svc_urb)
+               goto error;
+
+       usb_fill_int_urb(es1->svc_urb, udev,
+                        usb_rcvintpipe(udev, es1->svc_endpoint),
+                        es1->svc_buffer, ES1_SVC_MSG_SIZE, svc_in_callback,
+                        hd, svc_interval);
+       retval = usb_submit_urb(es1->svc_urb, GFP_KERNEL);
+       if (retval)
+               goto error;
+
+       /* Allocate buffers for our cport in messages and start them up */
+       for (i = 0; i < NUM_CPORT_IN_URB; ++i) {
+               struct urb *urb;
+               u8 *buffer;
+
+               urb = usb_alloc_urb(0, GFP_KERNEL);
+               if (!urb)
+                       goto error;
+               buffer = kmalloc(ES1_GBUF_MSG_SIZE_MAX, GFP_KERNEL);
+               if (!buffer)
+                       goto error;
+
+               usb_fill_bulk_urb(urb, udev,
+                                 usb_rcvbulkpipe(udev, es1->cport_in_endpoint),
+                                 buffer, ES1_GBUF_MSG_SIZE_MAX,
+                                 cport_in_callback, hd);
+               es1->cport_in_urb[i] = urb;
+               es1->cport_in_buffer[i] = buffer;
+               retval = usb_submit_urb(urb, GFP_KERNEL);
+               if (retval)
+                       goto error;
+       }
+
+       /* Allocate urbs for our CPort OUT messages */
+       for (i = 0; i < NUM_CPORT_OUT_URB; ++i) {
+               struct urb *urb;
+
+               urb = usb_alloc_urb(0, GFP_KERNEL);
+               if (!urb)
+                       goto error;
+
+               es1->cport_out_urb[i] = urb;
+               es1->cport_out_urb_busy[i] = false;     /* just to be anal */
+       }
+
+       return 0;
+error:
+       ap_disconnect(interface);
+
+       return retval;
+}
+
+static struct usb_driver es1_ap_driver = {
+       .name =         "es1_ap_driver",
+       .probe =        ap_probe,
+       .disconnect =   ap_disconnect,
+       .id_table =     id_table,
+};
+
+module_usb_driver(es1_ap_driver);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Greg Kroah-Hartman <gregkh@linuxfoundation.org>");