root/drivers/rpmsg/virtio_rpmsg_bus.c

DEFINITIONS

1. rpmsg_sg_init
2. __ept_release
3. __rpmsg_create_ept
4. virtio_rpmsg_create_ept
5. __rpmsg_destroy_ept
6. virtio_rpmsg_destroy_ept
7. virtio_rpmsg_announce_create
8. virtio_rpmsg_announce_destroy
9. virtio_rpmsg_release_device
10. rpmsg_create_channel
11. get_a_tx_buf
12. rpmsg_upref_sleepers
13. rpmsg_downref_sleepers
14. rpmsg_send_offchannel_raw
15. virtio_rpmsg_send
16. virtio_rpmsg_sendto
17. virtio_rpmsg_send_offchannel
18. virtio_rpmsg_trysend
19. virtio_rpmsg_trysendto
20. virtio_rpmsg_trysend_offchannel
21. rpmsg_recv_single
22. rpmsg_recv_done
23. rpmsg_xmit_done
24. rpmsg_ns_cb
25. rpmsg_probe
26. rpmsg_remove_device
27. rpmsg_remove
28. rpmsg_init
29. rpmsg_fini

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Virtio-based remote processor messaging bus
   4  *
   5  * Copyright (C) 2011 Texas Instruments, Inc.
   6  * Copyright (C) 2011 Google, Inc.
   7  *
   8  * Ohad Ben-Cohen <ohad@wizery.com>
   9  * Brian Swetland <swetland@google.com>
  10  */
  11 
  12 #define pr_fmt(fmt) "%s: " fmt, __func__
  13 
  14 #include <linux/dma-mapping.h>
  15 #include <linux/idr.h>
  16 #include <linux/jiffies.h>
  17 #include <linux/kernel.h>
  18 #include <linux/module.h>
  19 #include <linux/mutex.h>
  20 #include <linux/of_device.h>
  21 #include <linux/rpmsg.h>
  22 #include <linux/scatterlist.h>
  23 #include <linux/slab.h>
  24 #include <linux/sched.h>
  25 #include <linux/virtio.h>
  26 #include <linux/virtio_ids.h>
  27 #include <linux/virtio_config.h>
  28 #include <linux/wait.h>
  29 
  30 #include "rpmsg_internal.h"
  31 
  32 /**
  33  * struct virtproc_info - virtual remote processor state
  34  * @vdev:       the virtio device
  35  * @rvq:        rx virtqueue
  36  * @svq:        tx virtqueue
  37  * @rbufs:      kernel address of rx buffers
  38  * @sbufs:      kernel address of tx buffers
  39  * @num_bufs:   total number of buffers for rx and tx
  40  * @buf_size:   size of one rx or tx buffer
  41  * @last_sbuf:  index of last tx buffer used
  42  * @bufs_dma:   dma base addr of the buffers
  43  * @tx_lock:    protects svq, sbufs and sleepers, to allow concurrent senders.
  44  *              sending a message might require waking up a dozing remote
  45  *              processor, which involves sleeping, hence the mutex.
  46  * @endpoints:  idr of local endpoints, allows fast retrieval
  47  * @endpoints_lock: lock of the endpoints set
  48  * @sendq:      wait queue of sending contexts waiting for a tx buffers
  49  * @sleepers:   number of senders that are waiting for a tx buffer
  50  * @ns_ept:     the bus's name service endpoint
  51  *
  52  * This structure stores the rpmsg state of a given virtio remote processor
  53  * device (there might be several virtio proc devices for each physical
  54  * remote processor).
  55  */
  56 struct virtproc_info {
  57         struct virtio_device *vdev;
  58         struct virtqueue *rvq, *svq;
  59         void *rbufs, *sbufs;
  60         unsigned int num_bufs;
  61         unsigned int buf_size;
  62         int last_sbuf;
  63         dma_addr_t bufs_dma;
  64         struct mutex tx_lock;
  65         struct idr endpoints;
  66         struct mutex endpoints_lock;
  67         wait_queue_head_t sendq;
  68         atomic_t sleepers;
  69         struct rpmsg_endpoint *ns_ept;
  70 };
  71 
  72 /* The feature bitmap for virtio rpmsg */
  73 #define VIRTIO_RPMSG_F_NS       0 /* RP supports name service notifications */
  74 
  75 /**
  76  * struct rpmsg_hdr - common header for all rpmsg messages
  77  * @src: source address
  78  * @dst: destination address
  79  * @reserved: reserved for future use
  80  * @len: length of payload (in bytes)
  81  * @flags: message flags
  82  * @data: @len bytes of message payload data
  83  *
  84  * Every message sent(/received) on the rpmsg bus begins with this header.
  85  */
  86 struct rpmsg_hdr {
  87         u32 src;
  88         u32 dst;
  89         u32 reserved;
  90         u16 len;
  91         u16 flags;
  92         u8 data[0];
  93 } __packed;
  94 
  95 /**
  96  * struct rpmsg_ns_msg - dynamic name service announcement message
  97  * @name: name of remote service that is published
  98  * @addr: address of remote service that is published
  99  * @flags: indicates whether service is created or destroyed
 100  *
 101  * This message is sent across to publish a new service, or announce
 102  * about its removal. When we receive these messages, an appropriate
 103  * rpmsg channel (i.e device) is created/destroyed. In turn, the ->probe()
 104  * or ->remove() handler of the appropriate rpmsg driver will be invoked
 105  * (if/as-soon-as one is registered).
 106  */
 107 struct rpmsg_ns_msg {
 108         char name[RPMSG_NAME_SIZE];
 109         u32 addr;
 110         u32 flags;
 111 } __packed;
 112 
 113 /**
 114  * enum rpmsg_ns_flags - dynamic name service announcement flags
 115  *
 116  * @RPMSG_NS_CREATE: a new remote service was just created
 117  * @RPMSG_NS_DESTROY: a known remote service was just destroyed
 118  */
 119 enum rpmsg_ns_flags {
 120         RPMSG_NS_CREATE         = 0,
 121         RPMSG_NS_DESTROY        = 1,
 122 };
 123 
 124 /**
 125  * @vrp: the remote processor this channel belongs to
 126  */
 127 struct virtio_rpmsg_channel {
 128         struct rpmsg_device rpdev;
 129 
 130         struct virtproc_info *vrp;
 131 };
 132 
 133 #define to_virtio_rpmsg_channel(_rpdev) \
 134         container_of(_rpdev, struct virtio_rpmsg_channel, rpdev)
 135 
 136 /*
 137  * We're allocating buffers of 512 bytes each for communications. The
 138  * number of buffers will be computed from the number of buffers supported
 139  * by the vring, upto a maximum of 512 buffers (256 in each direction).
 140  *
 141  * Each buffer will have 16 bytes for the msg header and 496 bytes for
 142  * the payload.
 143  *
 144  * This will utilize a maximum total space of 256KB for the buffers.
 145  *
 146  * We might also want to add support for user-provided buffers in time.
 147  * This will allow bigger buffer size flexibility, and can also be used
 148  * to achieve zero-copy messaging.
 149  *
 150  * Note that these numbers are purely a decision of this driver - we
 151  * can change this without changing anything in the firmware of the remote
 152  * processor.
 153  */
 154 #define MAX_RPMSG_NUM_BUFS      (512)
 155 #define MAX_RPMSG_BUF_SIZE      (512)
 156 
 157 /*
 158  * Local addresses are dynamically allocated on-demand.
 159  * We do not dynamically assign addresses from the low 1024 range,
 160  * in order to reserve that address range for predefined services.
 161  */
 162 #define RPMSG_RESERVED_ADDRESSES        (1024)
 163 
 164 /* Address 53 is reserved for advertising remote services */
 165 #define RPMSG_NS_ADDR                   (53)
 166 
 167 static void virtio_rpmsg_destroy_ept(struct rpmsg_endpoint *ept);
 168 static int virtio_rpmsg_send(struct rpmsg_endpoint *ept, void *data, int len);
 169 static int virtio_rpmsg_sendto(struct rpmsg_endpoint *ept, void *data, int len,
 170                                u32 dst);
 171 static int virtio_rpmsg_send_offchannel(struct rpmsg_endpoint *ept, u32 src,
 172                                         u32 dst, void *data, int len);
 173 static int virtio_rpmsg_trysend(struct rpmsg_endpoint *ept, void *data, int len);
 174 static int virtio_rpmsg_trysendto(struct rpmsg_endpoint *ept, void *data,
 175                                   int len, u32 dst);
 176 static int virtio_rpmsg_trysend_offchannel(struct rpmsg_endpoint *ept, u32 src,
 177                                            u32 dst, void *data, int len);
 178 
 179 static const struct rpmsg_endpoint_ops virtio_endpoint_ops = {
 180         .destroy_ept = virtio_rpmsg_destroy_ept,
 181         .send = virtio_rpmsg_send,
 182         .sendto = virtio_rpmsg_sendto,
 183         .send_offchannel = virtio_rpmsg_send_offchannel,
 184         .trysend = virtio_rpmsg_trysend,
 185         .trysendto = virtio_rpmsg_trysendto,
 186         .trysend_offchannel = virtio_rpmsg_trysend_offchannel,
 187 };
 188 
 189 /**
 190  * rpmsg_sg_init - initialize scatterlist according to cpu address location
 191  * @sg: scatterlist to fill
 192  * @cpu_addr: virtual address of the buffer
 193  * @len: buffer length
 194  *
 195  * An internal function filling scatterlist according to virtual address
 196  * location (in vmalloc or in kernel).
 197  */
 198 static void
 199 rpmsg_sg_init(struct scatterlist *sg, void *cpu_addr, unsigned int len)
 200 {
 201         if (is_vmalloc_addr(cpu_addr)) {
 202                 sg_init_table(sg, 1);
 203                 sg_set_page(sg, vmalloc_to_page(cpu_addr), len,
 204                             offset_in_page(cpu_addr));
 205         } else {
 206                 WARN_ON(!virt_addr_valid(cpu_addr));
 207                 sg_init_one(sg, cpu_addr, len);
 208         }
 209 }
 210 
 211 /**
 212  * __ept_release() - deallocate an rpmsg endpoint
 213  * @kref: the ept's reference count
 214  *
 215  * This function deallocates an ept, and is invoked when its @kref refcount
 216  * drops to zero.
 217  *
 218  * Never invoke this function directly!
 219  */
 220 static void __ept_release(struct kref *kref)
 221 {
 222         struct rpmsg_endpoint *ept = container_of(kref, struct rpmsg_endpoint,
 223                                                   refcount);
 224         /*
 225          * At this point no one holds a reference to ept anymore,
 226          * so we can directly free it
 227          */
 228         kfree(ept);
 229 }
 230 
 231 /* for more info, see below documentation of rpmsg_create_ept() */
 232 static struct rpmsg_endpoint *__rpmsg_create_ept(struct virtproc_info *vrp,
 233                                                  struct rpmsg_device *rpdev,
 234                                                  rpmsg_rx_cb_t cb,
 235                                                  void *priv, u32 addr)
 236 {
 237         int id_min, id_max, id;
 238         struct rpmsg_endpoint *ept;
 239         struct device *dev = rpdev ? &rpdev->dev : &vrp->vdev->dev;
 240 
 241         ept = kzalloc(sizeof(*ept), GFP_KERNEL);
 242         if (!ept)
 243                 return NULL;
 244 
 245         kref_init(&ept->refcount);
 246         mutex_init(&ept->cb_lock);
 247 
 248         ept->rpdev = rpdev;
 249         ept->cb = cb;
 250         ept->priv = priv;
 251         ept->ops = &virtio_endpoint_ops;
 252 
 253         /* do we need to allocate a local address ? */
 254         if (addr == RPMSG_ADDR_ANY) {
 255                 id_min = RPMSG_RESERVED_ADDRESSES;
 256                 id_max = 0;
 257         } else {
 258                 id_min = addr;
 259                 id_max = addr + 1;
 260         }
 261 
 262         mutex_lock(&vrp->endpoints_lock);
 263 
 264         /* bind the endpoint to an rpmsg address (and allocate one if needed) */
 265         id = idr_alloc(&vrp->endpoints, ept, id_min, id_max, GFP_KERNEL);
 266         if (id < 0) {
 267                 dev_err(dev, "idr_alloc failed: %d\n", id);
 268                 goto free_ept;
 269         }
 270         ept->addr = id;
 271 
 272         mutex_unlock(&vrp->endpoints_lock);
 273 
 274         return ept;
 275 
 276 free_ept:
 277         mutex_unlock(&vrp->endpoints_lock);
 278         kref_put(&ept->refcount, __ept_release);
 279         return NULL;
 280 }
 281 
 282 static struct rpmsg_endpoint *virtio_rpmsg_create_ept(struct rpmsg_device *rpdev,
 283                                                       rpmsg_rx_cb_t cb,
 284                                                       void *priv,
 285                                                       struct rpmsg_channel_info chinfo)
 286 {
 287         struct virtio_rpmsg_channel *vch = to_virtio_rpmsg_channel(rpdev);
 288 
 289         return __rpmsg_create_ept(vch->vrp, rpdev, cb, priv, chinfo.src);
 290 }
 291 
 292 /**
 293  * __rpmsg_destroy_ept() - destroy an existing rpmsg endpoint
 294  * @vrp: virtproc which owns this ept
 295  * @ept: endpoing to destroy
 296  *
 297  * An internal function which destroy an ept without assuming it is
 298  * bound to an rpmsg channel. This is needed for handling the internal
 299  * name service endpoint, which isn't bound to an rpmsg channel.
 300  * See also __rpmsg_create_ept().
 301  */
 302 static void
 303 __rpmsg_destroy_ept(struct virtproc_info *vrp, struct rpmsg_endpoint *ept)
 304 {
 305         /* make sure new inbound messages can't find this ept anymore */
 306         mutex_lock(&vrp->endpoints_lock);
 307         idr_remove(&vrp->endpoints, ept->addr);
 308         mutex_unlock(&vrp->endpoints_lock);
 309 
 310         /* make sure in-flight inbound messages won't invoke cb anymore */
 311         mutex_lock(&ept->cb_lock);
 312         ept->cb = NULL;
 313         mutex_unlock(&ept->cb_lock);
 314 
 315         kref_put(&ept->refcount, __ept_release);
 316 }
 317 
 318 static void virtio_rpmsg_destroy_ept(struct rpmsg_endpoint *ept)
 319 {
 320         struct virtio_rpmsg_channel *vch = to_virtio_rpmsg_channel(ept->rpdev);
 321 
 322         __rpmsg_destroy_ept(vch->vrp, ept);
 323 }
 324 
 325 static int virtio_rpmsg_announce_create(struct rpmsg_device *rpdev)
 326 {
 327         struct virtio_rpmsg_channel *vch = to_virtio_rpmsg_channel(rpdev);
 328         struct virtproc_info *vrp = vch->vrp;
 329         struct device *dev = &rpdev->dev;
 330         int err = 0;
 331 
 332         /* need to tell remote processor's name service about this channel ? */
 333         if (rpdev->announce && rpdev->ept &&
 334             virtio_has_feature(vrp->vdev, VIRTIO_RPMSG_F_NS)) {
 335                 struct rpmsg_ns_msg nsm;
 336 
 337                 strncpy(nsm.name, rpdev->id.name, RPMSG_NAME_SIZE);
 338                 nsm.addr = rpdev->ept->addr;
 339                 nsm.flags = RPMSG_NS_CREATE;
 340 
 341                 err = rpmsg_sendto(rpdev->ept, &nsm, sizeof(nsm), RPMSG_NS_ADDR);
 342                 if (err)
 343                         dev_err(dev, "failed to announce service %d\n", err);
 344         }
 345 
 346         return err;
 347 }
 348 
 349 static int virtio_rpmsg_announce_destroy(struct rpmsg_device *rpdev)
 350 {
 351         struct virtio_rpmsg_channel *vch = to_virtio_rpmsg_channel(rpdev);
 352         struct virtproc_info *vrp = vch->vrp;
 353         struct device *dev = &rpdev->dev;
 354         int err = 0;
 355 
 356         /* tell remote processor's name service we're removing this channel */
 357         if (rpdev->announce && rpdev->ept &&
 358             virtio_has_feature(vrp->vdev, VIRTIO_RPMSG_F_NS)) {
 359                 struct rpmsg_ns_msg nsm;
 360 
 361                 strncpy(nsm.name, rpdev->id.name, RPMSG_NAME_SIZE);
 362                 nsm.addr = rpdev->ept->addr;
 363                 nsm.flags = RPMSG_NS_DESTROY;
 364 
 365                 err = rpmsg_sendto(rpdev->ept, &nsm, sizeof(nsm), RPMSG_NS_ADDR);
 366                 if (err)
 367                         dev_err(dev, "failed to announce service %d\n", err);
 368         }
 369 
 370         return err;
 371 }
 372 
 373 static const struct rpmsg_device_ops virtio_rpmsg_ops = {
 374         .create_ept = virtio_rpmsg_create_ept,
 375         .announce_create = virtio_rpmsg_announce_create,
 376         .announce_destroy = virtio_rpmsg_announce_destroy,
 377 };
 378 
 379 static void virtio_rpmsg_release_device(struct device *dev)
 380 {
 381         struct rpmsg_device *rpdev = to_rpmsg_device(dev);
 382         struct virtio_rpmsg_channel *vch = to_virtio_rpmsg_channel(rpdev);
 383 
 384         kfree(vch);
 385 }
 386 
 387 /*
 388  * create an rpmsg channel using its name and address info.
 389  * this function will be used to create both static and dynamic
 390  * channels.
 391  */
 392 static struct rpmsg_device *rpmsg_create_channel(struct virtproc_info *vrp,
 393                                                  struct rpmsg_channel_info *chinfo)
 394 {
 395         struct virtio_rpmsg_channel *vch;
 396         struct rpmsg_device *rpdev;
 397         struct device *tmp, *dev = &vrp->vdev->dev;
 398         int ret;
 399 
 400         /* make sure a similar channel doesn't already exist */
 401         tmp = rpmsg_find_device(dev, chinfo);
 402         if (tmp) {
 403                 /* decrement the matched device's refcount back */
 404                 put_device(tmp);
 405                 dev_err(dev, "channel %s:%x:%x already exist\n",
 406                                 chinfo->name, chinfo->src, chinfo->dst);
 407                 return NULL;
 408         }
 409 
 410         vch = kzalloc(sizeof(*vch), GFP_KERNEL);
 411         if (!vch)
 412                 return NULL;
 413 
 414         /* Link the channel to our vrp */
 415         vch->vrp = vrp;
 416 
 417         /* Assign public information to the rpmsg_device */
 418         rpdev = &vch->rpdev;
 419         rpdev->src = chinfo->src;
 420         rpdev->dst = chinfo->dst;
 421         rpdev->ops = &virtio_rpmsg_ops;
 422 
 423         /*
 424          * rpmsg server channels has predefined local address (for now),
 425          * and their existence needs to be announced remotely
 426          */
 427         rpdev->announce = rpdev->src != RPMSG_ADDR_ANY;
 428 
 429         strncpy(rpdev->id.name, chinfo->name, RPMSG_NAME_SIZE);
 430 
 431         rpdev->dev.parent = &vrp->vdev->dev;
 432         rpdev->dev.release = virtio_rpmsg_release_device;
 433         ret = rpmsg_register_device(rpdev);
 434         if (ret)
 435                 return NULL;
 436 
 437         return rpdev;
 438 }
 439 
 440 /* super simple buffer "allocator" that is just enough for now */
 441 static void *get_a_tx_buf(struct virtproc_info *vrp)
 442 {
 443         unsigned int len;
 444         void *ret;
 445 
 446         /* support multiple concurrent senders */
 447         mutex_lock(&vrp->tx_lock);
 448 
 449         /*
 450          * either pick the next unused tx buffer
 451          * (half of our buffers are used for sending messages)
 452          */
 453         if (vrp->last_sbuf < vrp->num_bufs / 2)
 454                 ret = vrp->sbufs + vrp->buf_size * vrp->last_sbuf++;
 455         /* or recycle a used one */
 456         else
 457                 ret = virtqueue_get_buf(vrp->svq, &len);
 458 
 459         mutex_unlock(&vrp->tx_lock);
 460 
 461         return ret;
 462 }
 463 
 464 /**
 465  * rpmsg_upref_sleepers() - enable "tx-complete" interrupts, if needed
 466  * @vrp: virtual remote processor state
 467  *
 468  * This function is called before a sender is blocked, waiting for
 469  * a tx buffer to become available.
 470  *
 471  * If we already have blocking senders, this function merely increases
 472  * the "sleepers" reference count, and exits.
 473  *
 474  * Otherwise, if this is the first sender to block, we also enable
 475  * virtio's tx callbacks, so we'd be immediately notified when a tx
 476  * buffer is consumed (we rely on virtio's tx callback in order
 477  * to wake up sleeping senders as soon as a tx buffer is used by the
 478  * remote processor).
 479  */
 480 static void rpmsg_upref_sleepers(struct virtproc_info *vrp)
 481 {
 482         /* support multiple concurrent senders */
 483         mutex_lock(&vrp->tx_lock);
 484 
 485         /* are we the first sleeping context waiting for tx buffers ? */
 486         if (atomic_inc_return(&vrp->sleepers) == 1)
 487                 /* enable "tx-complete" interrupts before dozing off */
 488                 virtqueue_enable_cb(vrp->svq);
 489 
 490         mutex_unlock(&vrp->tx_lock);
 491 }
 492 
 493 /**
 494  * rpmsg_downref_sleepers() - disable "tx-complete" interrupts, if needed
 495  * @vrp: virtual remote processor state
 496  *
 497  * This function is called after a sender, that waited for a tx buffer
 498  * to become available, is unblocked.
 499  *
 500  * If we still have blocking senders, this function merely decreases
 501  * the "sleepers" reference count, and exits.
 502  *
 503  * Otherwise, if there are no more blocking senders, we also disable
 504  * virtio's tx callbacks, to avoid the overhead incurred with handling
 505  * those (now redundant) interrupts.
 506  */
 507 static void rpmsg_downref_sleepers(struct virtproc_info *vrp)
 508 {
 509         /* support multiple concurrent senders */
 510         mutex_lock(&vrp->tx_lock);
 511 
 512         /* are we the last sleeping context waiting for tx buffers ? */
 513         if (atomic_dec_and_test(&vrp->sleepers))
 514                 /* disable "tx-complete" interrupts */
 515                 virtqueue_disable_cb(vrp->svq);
 516 
 517         mutex_unlock(&vrp->tx_lock);
 518 }
 519 
 520 /**
 521  * rpmsg_send_offchannel_raw() - send a message across to the remote processor
 522  * @rpdev: the rpmsg channel
 523  * @src: source address
 524  * @dst: destination address
 525  * @data: payload of message
 526  * @len: length of payload
 527  * @wait: indicates whether caller should block in case no TX buffers available
 528  *
 529  * This function is the base implementation for all of the rpmsg sending API.
 530  *
 531  * It will send @data of length @len to @dst, and say it's from @src. The
 532  * message will be sent to the remote processor which the @rpdev channel
 533  * belongs to.
 534  *
 535  * The message is sent using one of the TX buffers that are available for
 536  * communication with this remote processor.
 537  *
 538  * If @wait is true, the caller will be blocked until either a TX buffer is
 539  * available, or 15 seconds elapses (we don't want callers to
 540  * sleep indefinitely due to misbehaving remote processors), and in that
 541  * case -ERESTARTSYS is returned. The number '15' itself was picked
 542  * arbitrarily; there's little point in asking drivers to provide a timeout
 543  * value themselves.
 544  *
 545  * Otherwise, if @wait is false, and there are no TX buffers available,
 546  * the function will immediately fail, and -ENOMEM will be returned.
 547  *
 548  * Normally drivers shouldn't use this function directly; instead, drivers
 549  * should use the appropriate rpmsg_{try}send{to, _offchannel} API
 550  * (see include/linux/rpmsg.h).
 551  *
 552  * Returns 0 on success and an appropriate error value on failure.
 553  */
 554 static int rpmsg_send_offchannel_raw(struct rpmsg_device *rpdev,
 555                                      u32 src, u32 dst,
 556                                      void *data, int len, bool wait)
 557 {
 558         struct virtio_rpmsg_channel *vch = to_virtio_rpmsg_channel(rpdev);
 559         struct virtproc_info *vrp = vch->vrp;
 560         struct device *dev = &rpdev->dev;
 561         struct scatterlist sg;
 562         struct rpmsg_hdr *msg;
 563         int err;
 564 
 565         /* bcasting isn't allowed */
 566         if (src == RPMSG_ADDR_ANY || dst == RPMSG_ADDR_ANY) {
 567                 dev_err(dev, "invalid addr (src 0x%x, dst 0x%x)\n", src, dst);
 568                 return -EINVAL;
 569         }
 570 
 571         /*
 572          * We currently use fixed-sized buffers, and therefore the payload
 573          * length is limited.
 574          *
 575          * One of the possible improvements here is either to support
 576          * user-provided buffers (and then we can also support zero-copy
 577          * messaging), or to improve the buffer allocator, to support
 578          * variable-length buffer sizes.
 579          */
 580         if (len > vrp->buf_size - sizeof(struct rpmsg_hdr)) {
 581                 dev_err(dev, "message is too big (%d)\n", len);
 582                 return -EMSGSIZE;
 583         }
 584 
 585         /* grab a buffer */
 586         msg = get_a_tx_buf(vrp);
 587         if (!msg && !wait)
 588                 return -ENOMEM;
 589 
 590         /* no free buffer ? wait for one (but bail after 15 seconds) */
 591         while (!msg) {
 592                 /* enable "tx-complete" interrupts, if not already enabled */
 593                 rpmsg_upref_sleepers(vrp);
 594 
 595                 /*
 596                  * sleep until a free buffer is available or 15 secs elapse.
 597                  * the timeout period is not configurable because there's
 598                  * little point in asking drivers to specify that.
 599                  * if later this happens to be required, it'd be easy to add.
 600                  */
 601                 err = wait_event_interruptible_timeout(vrp->sendq,
 602                                         (msg = get_a_tx_buf(vrp)),
 603                                         msecs_to_jiffies(15000));
 604 
 605                 /* disable "tx-complete" interrupts if we're the last sleeper */
 606                 rpmsg_downref_sleepers(vrp);
 607 
 608                 /* timeout ? */
 609                 if (!err) {
 610                         dev_err(dev, "timeout waiting for a tx buffer\n");
 611                         return -ERESTARTSYS;
 612                 }
 613         }
 614 
 615         msg->len = len;
 616         msg->flags = 0;
 617         msg->src = src;
 618         msg->dst = dst;
 619         msg->reserved = 0;
 620         memcpy(msg->data, data, len);
 621 
 622         dev_dbg(dev, "TX From 0x%x, To 0x%x, Len %d, Flags %d, Reserved %d\n",
 623                 msg->src, msg->dst, msg->len, msg->flags, msg->reserved);
 624 #if defined(CONFIG_DYNAMIC_DEBUG)
 625         dynamic_hex_dump("rpmsg_virtio TX: ", DUMP_PREFIX_NONE, 16, 1,
 626                          msg, sizeof(*msg) + msg->len, true);
 627 #endif
 628 
 629         rpmsg_sg_init(&sg, msg, sizeof(*msg) + len);
 630 
 631         mutex_lock(&vrp->tx_lock);
 632 
 633         /* add message to the remote processor's virtqueue */
 634         err = virtqueue_add_outbuf(vrp->svq, &sg, 1, msg, GFP_KERNEL);
 635         if (err) {
 636                 /*
 637                  * need to reclaim the buffer here, otherwise it's lost
 638                  * (memory won't leak, but rpmsg won't use it again for TX).
 639                  * this will wait for a buffer management overhaul.
 640                  */
 641                 dev_err(dev, "virtqueue_add_outbuf failed: %d\n", err);
 642                 goto out;
 643         }
 644 
 645         /* tell the remote processor it has a pending message to read */
 646         virtqueue_kick(vrp->svq);
 647 out:
 648         mutex_unlock(&vrp->tx_lock);
 649         return err;
 650 }
 651 
 652 static int virtio_rpmsg_send(struct rpmsg_endpoint *ept, void *data, int len)
 653 {
 654         struct rpmsg_device *rpdev = ept->rpdev;
 655         u32 src = ept->addr, dst = rpdev->dst;
 656 
 657         return rpmsg_send_offchannel_raw(rpdev, src, dst, data, len, true);
 658 }
 659 
 660 static int virtio_rpmsg_sendto(struct rpmsg_endpoint *ept, void *data, int len,
 661                                u32 dst)
 662 {
 663         struct rpmsg_device *rpdev = ept->rpdev;
 664         u32 src = ept->addr;
 665 
 666         return rpmsg_send_offchannel_raw(rpdev, src, dst, data, len, true);
 667 }
 668 
 669 static int virtio_rpmsg_send_offchannel(struct rpmsg_endpoint *ept, u32 src,
 670                                         u32 dst, void *data, int len)
 671 {
 672         struct rpmsg_device *rpdev = ept->rpdev;
 673 
 674         return rpmsg_send_offchannel_raw(rpdev, src, dst, data, len, true);
 675 }
 676 
 677 static int virtio_rpmsg_trysend(struct rpmsg_endpoint *ept, void *data, int len)
 678 {
 679         struct rpmsg_device *rpdev = ept->rpdev;
 680         u32 src = ept->addr, dst = rpdev->dst;
 681 
 682         return rpmsg_send_offchannel_raw(rpdev, src, dst, data, len, false);
 683 }
 684 
 685 static int virtio_rpmsg_trysendto(struct rpmsg_endpoint *ept, void *data,
 686                                   int len, u32 dst)
 687 {
 688         struct rpmsg_device *rpdev = ept->rpdev;
 689         u32 src = ept->addr;
 690 
 691         return rpmsg_send_offchannel_raw(rpdev, src, dst, data, len, false);
 692 }
 693 
 694 static int virtio_rpmsg_trysend_offchannel(struct rpmsg_endpoint *ept, u32 src,
 695                                            u32 dst, void *data, int len)
 696 {
 697         struct rpmsg_device *rpdev = ept->rpdev;
 698 
 699         return rpmsg_send_offchannel_raw(rpdev, src, dst, data, len, false);
 700 }
 701 
 702 static int rpmsg_recv_single(struct virtproc_info *vrp, struct device *dev,
 703                              struct rpmsg_hdr *msg, unsigned int len)
 704 {
 705         struct rpmsg_endpoint *ept;
 706         struct scatterlist sg;
 707         int err;
 708 
 709         dev_dbg(dev, "From: 0x%x, To: 0x%x, Len: %d, Flags: %d, Reserved: %d\n",
 710                 msg->src, msg->dst, msg->len, msg->flags, msg->reserved);
 711 #if defined(CONFIG_DYNAMIC_DEBUG)
 712         dynamic_hex_dump("rpmsg_virtio RX: ", DUMP_PREFIX_NONE, 16, 1,
 713                          msg, sizeof(*msg) + msg->len, true);
 714 #endif
 715 
 716         /*
 717          * We currently use fixed-sized buffers, so trivially sanitize
 718          * the reported payload length.
 719          */
 720         if (len > vrp->buf_size ||
 721             msg->len > (len - sizeof(struct rpmsg_hdr))) {
 722                 dev_warn(dev, "inbound msg too big: (%d, %d)\n", len, msg->len);
 723                 return -EINVAL;
 724         }
 725 
 726         /* use the dst addr to fetch the callback of the appropriate user */
 727         mutex_lock(&vrp->endpoints_lock);
 728 
 729         ept = idr_find(&vrp->endpoints, msg->dst);
 730 
 731         /* let's make sure no one deallocates ept while we use it */
 732         if (ept)
 733                 kref_get(&ept->refcount);
 734 
 735         mutex_unlock(&vrp->endpoints_lock);
 736 
 737         if (ept) {
 738                 /* make sure ept->cb doesn't go away while we use it */
 739                 mutex_lock(&ept->cb_lock);
 740 
 741                 if (ept->cb)
 742                         ept->cb(ept->rpdev, msg->data, msg->len, ept->priv,
 743                                 msg->src);
 744 
 745                 mutex_unlock(&ept->cb_lock);
 746 
 747                 /* farewell, ept, we don't need you anymore */
 748                 kref_put(&ept->refcount, __ept_release);
 749         } else
 750                 dev_warn(dev, "msg received with no recipient\n");
 751 
 752         /* publish the real size of the buffer */
 753         rpmsg_sg_init(&sg, msg, vrp->buf_size);
 754 
 755         /* add the buffer back to the remote processor's virtqueue */
 756         err = virtqueue_add_inbuf(vrp->rvq, &sg, 1, msg, GFP_KERNEL);
 757         if (err < 0) {
 758                 dev_err(dev, "failed to add a virtqueue buffer: %d\n", err);
 759                 return err;
 760         }
 761 
 762         return 0;
 763 }
 764 
 765 /* called when an rx buffer is used, and it's time to digest a message */
 766 static void rpmsg_recv_done(struct virtqueue *rvq)
 767 {
 768         struct virtproc_info *vrp = rvq->vdev->priv;
 769         struct device *dev = &rvq->vdev->dev;
 770         struct rpmsg_hdr *msg;
 771         unsigned int len, msgs_received = 0;
 772         int err;
 773 
 774         msg = virtqueue_get_buf(rvq, &len);
 775         if (!msg) {
 776                 dev_err(dev, "uhm, incoming signal, but no used buffer ?\n");
 777                 return;
 778         }
 779 
 780         while (msg) {
 781                 err = rpmsg_recv_single(vrp, dev, msg, len);
 782                 if (err)
 783                         break;
 784 
 785                 msgs_received++;
 786 
 787                 msg = virtqueue_get_buf(rvq, &len);
 788         }
 789 
 790         dev_dbg(dev, "Received %u messages\n", msgs_received);
 791 
 792         /* tell the remote processor we added another available rx buffer */
 793         if (msgs_received)
 794                 virtqueue_kick(vrp->rvq);
 795 }
 796 
 797 /*
 798  * This is invoked whenever the remote processor completed processing
 799  * a TX msg we just sent it, and the buffer is put back to the used ring.
 800  *
 801  * Normally, though, we suppress this "tx complete" interrupt in order to
 802  * avoid the incurred overhead.
 803  */
 804 static void rpmsg_xmit_done(struct virtqueue *svq)
 805 {
 806         struct virtproc_info *vrp = svq->vdev->priv;
 807 
 808         dev_dbg(&svq->vdev->dev, "%s\n", __func__);
 809 
 810         /* wake up potential senders that are waiting for a tx buffer */
 811         wake_up_interruptible(&vrp->sendq);
 812 }
 813 
 814 /* invoked when a name service announcement arrives */
 815 static int rpmsg_ns_cb(struct rpmsg_device *rpdev, void *data, int len,
 816                        void *priv, u32 src)
 817 {
 818         struct rpmsg_ns_msg *msg = data;
 819         struct rpmsg_device *newch;
 820         struct rpmsg_channel_info chinfo;
 821         struct virtproc_info *vrp = priv;
 822         struct device *dev = &vrp->vdev->dev;
 823         int ret;
 824 
 825 #if defined(CONFIG_DYNAMIC_DEBUG)
 826         dynamic_hex_dump("NS announcement: ", DUMP_PREFIX_NONE, 16, 1,
 827                          data, len, true);
 828 #endif
 829 
 830         if (len != sizeof(*msg)) {
 831                 dev_err(dev, "malformed ns msg (%d)\n", len);
 832                 return -EINVAL;
 833         }
 834 
 835         /*
 836          * the name service ept does _not_ belong to a real rpmsg channel,
 837          * and is handled by the rpmsg bus itself.
 838          * for sanity reasons, make sure a valid rpdev has _not_ sneaked
 839          * in somehow.
 840          */
 841         if (rpdev) {
 842                 dev_err(dev, "anomaly: ns ept has an rpdev handle\n");
 843                 return -EINVAL;
 844         }
 845 
 846         /* don't trust the remote processor for null terminating the name */
 847         msg->name[RPMSG_NAME_SIZE - 1] = '\0';
 848 
 849         dev_info(dev, "%sing channel %s addr 0x%x\n",
 850                  msg->flags & RPMSG_NS_DESTROY ? "destroy" : "creat",
 851                  msg->name, msg->addr);
 852 
 853         strncpy(chinfo.name, msg->name, sizeof(chinfo.name));
 854         chinfo.src = RPMSG_ADDR_ANY;
 855         chinfo.dst = msg->addr;
 856 
 857         if (msg->flags & RPMSG_NS_DESTROY) {
 858                 ret = rpmsg_unregister_device(&vrp->vdev->dev, &chinfo);
 859                 if (ret)
 860                         dev_err(dev, "rpmsg_destroy_channel failed: %d\n", ret);
 861         } else {
 862                 newch = rpmsg_create_channel(vrp, &chinfo);
 863                 if (!newch)
 864                         dev_err(dev, "rpmsg_create_channel failed\n");
 865         }
 866 
 867         return 0;
 868 }
 869 
 870 static int rpmsg_probe(struct virtio_device *vdev)
 871 {
 872         vq_callback_t *vq_cbs[] = { rpmsg_recv_done, rpmsg_xmit_done };
 873         static const char * const names[] = { "input", "output" };
 874         struct virtqueue *vqs[2];
 875         struct virtproc_info *vrp;
 876         void *bufs_va;
 877         int err = 0, i;
 878         size_t total_buf_space;
 879         bool notify;
 880 
 881         vrp = kzalloc(sizeof(*vrp), GFP_KERNEL);
 882         if (!vrp)
 883                 return -ENOMEM;
 884 
 885         vrp->vdev = vdev;
 886 
 887         idr_init(&vrp->endpoints);
 888         mutex_init(&vrp->endpoints_lock);
 889         mutex_init(&vrp->tx_lock);
 890         init_waitqueue_head(&vrp->sendq);
 891 
 892         /* We expect two virtqueues, rx and tx (and in this order) */
 893         err = virtio_find_vqs(vdev, 2, vqs, vq_cbs, names, NULL);
 894         if (err)
 895                 goto free_vrp;
 896 
 897         vrp->rvq = vqs[0];
 898         vrp->svq = vqs[1];
 899 
 900         /* we expect symmetric tx/rx vrings */
 901         WARN_ON(virtqueue_get_vring_size(vrp->rvq) !=
 902                 virtqueue_get_vring_size(vrp->svq));
 903 
 904         /* we need less buffers if vrings are small */
 905         if (virtqueue_get_vring_size(vrp->rvq) < MAX_RPMSG_NUM_BUFS / 2)
 906                 vrp->num_bufs = virtqueue_get_vring_size(vrp->rvq) * 2;
 907         else
 908                 vrp->num_bufs = MAX_RPMSG_NUM_BUFS;
 909 
 910         vrp->buf_size = MAX_RPMSG_BUF_SIZE;
 911 
 912         total_buf_space = vrp->num_bufs * vrp->buf_size;
 913 
 914         /* allocate coherent memory for the buffers */
 915         bufs_va = dma_alloc_coherent(vdev->dev.parent,
 916                                      total_buf_space, &vrp->bufs_dma,
 917                                      GFP_KERNEL);
 918         if (!bufs_va) {
 919                 err = -ENOMEM;
 920                 goto vqs_del;
 921         }
 922 
 923         dev_dbg(&vdev->dev, "buffers: va %pK, dma %pad\n",
 924                 bufs_va, &vrp->bufs_dma);
 925 
 926         /* half of the buffers is dedicated for RX */
 927         vrp->rbufs = bufs_va;
 928 
 929         /* and half is dedicated for TX */
 930         vrp->sbufs = bufs_va + total_buf_space / 2;
 931 
 932         /* set up the receive buffers */
 933         for (i = 0; i < vrp->num_bufs / 2; i++) {
 934                 struct scatterlist sg;
 935                 void *cpu_addr = vrp->rbufs + i * vrp->buf_size;
 936 
 937                 rpmsg_sg_init(&sg, cpu_addr, vrp->buf_size);
 938 
 939                 err = virtqueue_add_inbuf(vrp->rvq, &sg, 1, cpu_addr,
 940                                           GFP_KERNEL);
 941                 WARN_ON(err); /* sanity check; this can't really happen */
 942         }
 943 
 944         /* suppress "tx-complete" interrupts */
 945         virtqueue_disable_cb(vrp->svq);
 946 
 947         vdev->priv = vrp;
 948 
 949         /* if supported by the remote processor, enable the name service */
 950         if (virtio_has_feature(vdev, VIRTIO_RPMSG_F_NS)) {
 951                 /* a dedicated endpoint handles the name service msgs */
 952                 vrp->ns_ept = __rpmsg_create_ept(vrp, NULL, rpmsg_ns_cb,
 953                                                 vrp, RPMSG_NS_ADDR);
 954                 if (!vrp->ns_ept) {
 955                         dev_err(&vdev->dev, "failed to create the ns ept\n");
 956                         err = -ENOMEM;
 957                         goto free_coherent;
 958                 }
 959         }
 960 
 961         /*
 962          * Prepare to kick but don't notify yet - we can't do this before
 963          * device is ready.
 964          */
 965         notify = virtqueue_kick_prepare(vrp->rvq);
 966 
 967         /* From this point on, we can notify and get callbacks. */
 968         virtio_device_ready(vdev);
 969 
 970         /* tell the remote processor it can start sending messages */
 971         /*
 972          * this might be concurrent with callbacks, but we are only
 973          * doing notify, not a full kick here, so that's ok.
 974          */
 975         if (notify)
 976                 virtqueue_notify(vrp->rvq);
 977 
 978         dev_info(&vdev->dev, "rpmsg host is online\n");
 979 
 980         return 0;
 981 
 982 free_coherent:
 983         dma_free_coherent(vdev->dev.parent, total_buf_space,
 984                           bufs_va, vrp->bufs_dma);
 985 vqs_del:
 986         vdev->config->del_vqs(vrp->vdev);
 987 free_vrp:
 988         kfree(vrp);
 989         return err;
 990 }
 991 
 992 static int rpmsg_remove_device(struct device *dev, void *data)
 993 {
 994         device_unregister(dev);
 995 
 996         return 0;
 997 }
 998 
 999 static void rpmsg_remove(struct virtio_device *vdev)
1000 {
1001         struct virtproc_info *vrp = vdev->priv;
1002         size_t total_buf_space = vrp->num_bufs * vrp->buf_size;
1003         int ret;
1004 
1005         vdev->config->reset(vdev);
1006 
1007         ret = device_for_each_child(&vdev->dev, NULL, rpmsg_remove_device);
1008         if (ret)
1009                 dev_warn(&vdev->dev, "can't remove rpmsg device: %d\n", ret);
1010 
1011         if (vrp->ns_ept)
1012                 __rpmsg_destroy_ept(vrp, vrp->ns_ept);
1013 
1014         idr_destroy(&vrp->endpoints);
1015 
1016         vdev->config->del_vqs(vrp->vdev);
1017 
1018         dma_free_coherent(vdev->dev.parent, total_buf_space,
1019                           vrp->rbufs, vrp->bufs_dma);
1020 
1021         kfree(vrp);
1022 }
1023 
1024 static struct virtio_device_id id_table[] = {
1025         { VIRTIO_ID_RPMSG, VIRTIO_DEV_ANY_ID },
1026         { 0 },
1027 };
1028 
1029 static unsigned int features[] = {
1030         VIRTIO_RPMSG_F_NS,
1031 };
1032 
1033 static struct virtio_driver virtio_ipc_driver = {
1034         .feature_table  = features,
1035         .feature_table_size = ARRAY_SIZE(features),
1036         .driver.name    = KBUILD_MODNAME,
1037         .driver.owner   = THIS_MODULE,
1038         .id_table       = id_table,
1039         .probe          = rpmsg_probe,
1040         .remove         = rpmsg_remove,
1041 };
1042 
1043 static int __init rpmsg_init(void)
1044 {
1045         int ret;
1046 
1047         ret = register_virtio_driver(&virtio_ipc_driver);
1048         if (ret)
1049                 pr_err("failed to register virtio driver: %d\n", ret);
1050 
1051         return ret;
1052 }
1053 subsys_initcall(rpmsg_init);
1054 
1055 static void __exit rpmsg_fini(void)
1056 {
1057         unregister_virtio_driver(&virtio_ipc_driver);
1058 }
1059 module_exit(rpmsg_fini);
1060 
1061 MODULE_DEVICE_TABLE(virtio, id_table);
1062 MODULE_DESCRIPTION("Virtio-based remote processor messaging bus");
1063 MODULE_LICENSE("GPL v2");