root/drivers/platform/goldfish/goldfish_pipe.c

DEFINITIONS

1. goldfish_pipe_cmd_locked
2. goldfish_pipe_cmd
3. goldfish_pipe_error_convert
4. pin_user_pages
5. release_user_pages
6. populate_rw_params
7. transfer_max_buffers
8. wait_for_host_signal
9. goldfish_pipe_read_write
10. goldfish_pipe_read
11. goldfish_pipe_write
12. goldfish_pipe_poll
13. signalled_pipes_add_locked
14. signalled_pipes_remove_locked
15. signalled_pipes_pop_front
16. goldfish_interrupt_task
17. goldfish_pipe_interrupt
18. get_free_pipe_id_locked
19. to_goldfish_pipe_dev
20. goldfish_pipe_open
21. goldfish_pipe_release
22. init_miscdevice
23. write_pa_addr
24. goldfish_pipe_device_init
25. goldfish_pipe_device_deinit
26. goldfish_pipe_probe
27. goldfish_pipe_remove

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Copyright (C) 2012 Intel, Inc.
   4  * Copyright (C) 2013 Intel, Inc.
   5  * Copyright (C) 2014 Linaro Limited
   6  * Copyright (C) 2011-2016 Google, Inc.
   7  *
   8  * This software is licensed under the terms of the GNU General Public
   9  * License version 2, as published by the Free Software Foundation, and
  10  * may be copied, distributed, and modified under those terms.
  11  *
  12  * This program is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  * GNU General Public License for more details.
  16  *
  17  */
  18 
  19 /* This source file contains the implementation of a special device driver
  20  * that intends to provide a *very* fast communication channel between the
  21  * guest system and the QEMU emulator.
  22  *
  23  * Usage from the guest is simply the following (error handling simplified):
  24  *
  25  *    int  fd = open("/dev/qemu_pipe",O_RDWR);
  26  *    .... write() or read() through the pipe.
  27  *
  28  * This driver doesn't deal with the exact protocol used during the session.
  29  * It is intended to be as simple as something like:
  30  *
  31  *    // do this _just_ after opening the fd to connect to a specific
  32  *    // emulator service.
  33  *    const char*  msg = "<pipename>";
  34  *    if (write(fd, msg, strlen(msg)+1) < 0) {
  35  *       ... could not connect to <pipename> service
  36  *       close(fd);
  37  *    }
  38  *
  39  *    // after this, simply read() and write() to communicate with the
  40  *    // service. Exact protocol details left as an exercise to the reader.
  41  *
  42  * This driver is very fast because it doesn't copy any data through
  43  * intermediate buffers, since the emulator is capable of translating
  44  * guest user addresses into host ones.
  45  *
  46  * Note that we must however ensure that each user page involved in the
  47  * exchange is properly mapped during a transfer.
  48  */
  49 
  50 #include <linux/module.h>
  51 #include <linux/mod_devicetable.h>
  52 #include <linux/interrupt.h>
  53 #include <linux/kernel.h>
  54 #include <linux/spinlock.h>
  55 #include <linux/miscdevice.h>
  56 #include <linux/platform_device.h>
  57 #include <linux/poll.h>
  58 #include <linux/sched.h>
  59 #include <linux/bitops.h>
  60 #include <linux/slab.h>
  61 #include <linux/io.h>
  62 #include <linux/dma-mapping.h>
  63 #include <linux/mm.h>
  64 #include <linux/acpi.h>
  65 #include <linux/bug.h>
  66 #include "goldfish_pipe_qemu.h"
  67 
  68 /*
  69  * Update this when something changes in the driver's behavior so the host
  70  * can benefit from knowing it
  71  */
  72 enum {
  73         PIPE_DRIVER_VERSION = 2,
  74         PIPE_CURRENT_DEVICE_VERSION = 2
  75 };
  76 
  77 enum {
  78         MAX_BUFFERS_PER_COMMAND = 336,
  79         MAX_SIGNALLED_PIPES = 64,
  80         INITIAL_PIPES_CAPACITY = 64
  81 };
  82 
  83 struct goldfish_pipe_dev;
  84 
  85 /* A per-pipe command structure, shared with the host */
  86 struct goldfish_pipe_command {
  87         s32 cmd;        /* PipeCmdCode, guest -> host */
  88         s32 id;         /* pipe id, guest -> host */
  89         s32 status;     /* command execution status, host -> guest */
  90         s32 reserved;   /* to pad to 64-bit boundary */
  91         union {
  92                 /* Parameters for PIPE_CMD_{READ,WRITE} */
  93                 struct {
  94                         /* number of buffers, guest -> host */
  95                         u32 buffers_count;
  96                         /* number of consumed bytes, host -> guest */
  97                         s32 consumed_size;
  98                         /* buffer pointers, guest -> host */
  99                         u64 ptrs[MAX_BUFFERS_PER_COMMAND];
 100                         /* buffer sizes, guest -> host */
 101                         u32 sizes[MAX_BUFFERS_PER_COMMAND];
 102                 } rw_params;
 103         };
 104 };
 105 
 106 /* A single signalled pipe information */
 107 struct signalled_pipe_buffer {
 108         u32 id;
 109         u32 flags;
 110 };
 111 
 112 /* Parameters for the PIPE_CMD_OPEN command */
 113 struct open_command_param {
 114         u64 command_buffer_ptr;
 115         u32 rw_params_max_count;
 116 };
 117 
 118 /* Device-level set of buffers shared with the host */
 119 struct goldfish_pipe_dev_buffers {
 120         struct open_command_param open_command_params;
 121         struct signalled_pipe_buffer
 122                 signalled_pipe_buffers[MAX_SIGNALLED_PIPES];
 123 };
 124 
 125 /* This data type models a given pipe instance */
 126 struct goldfish_pipe {
 127         /* pipe ID - index into goldfish_pipe_dev::pipes array */
 128         u32 id;
 129 
 130         /* The wake flags pipe is waiting for
 131          * Note: not protected with any lock, uses atomic operations
 132          *  and barriers to make it thread-safe.
 133          */
 134         unsigned long flags;
 135 
 136         /* wake flags host have signalled,
 137          *  - protected by goldfish_pipe_dev::lock
 138          */
 139         unsigned long signalled_flags;
 140 
 141         /* A pointer to command buffer */
 142         struct goldfish_pipe_command *command_buffer;
 143 
 144         /* doubly linked list of signalled pipes, protected by
 145          * goldfish_pipe_dev::lock
 146          */
 147         struct goldfish_pipe *prev_signalled;
 148         struct goldfish_pipe *next_signalled;
 149 
 150         /*
 151          * A pipe's own lock. Protects the following:
 152          *  - *command_buffer - makes sure a command can safely write its
 153          *    parameters to the host and read the results back.
 154          */
 155         struct mutex lock;
 156 
 157         /* A wake queue for sleeping until host signals an event */
 158         wait_queue_head_t wake_queue;
 159 
 160         /* Pointer to the parent goldfish_pipe_dev instance */
 161         struct goldfish_pipe_dev *dev;
 162 
 163         /* A buffer of pages, too large to fit into a stack frame */
 164         struct page *pages[MAX_BUFFERS_PER_COMMAND];
 165 };
 166 
 167 /* The global driver data. Holds a reference to the i/o page used to
 168  * communicate with the emulator, and a wake queue for blocked tasks
 169  * waiting to be awoken.
 170  */
 171 struct goldfish_pipe_dev {
 172         /* A magic number to check if this is an instance of this struct */
 173         void *magic;
 174 
 175         /*
 176          * Global device spinlock. Protects the following members:
 177          *  - pipes, pipes_capacity
 178          *  - [*pipes, *pipes + pipes_capacity) - array data
 179          *  - first_signalled_pipe,
 180          *      goldfish_pipe::prev_signalled,
 181          *      goldfish_pipe::next_signalled,
 182          *      goldfish_pipe::signalled_flags - all singnalled-related fields,
 183          *                                       in all allocated pipes
 184          *  - open_command_params - PIPE_CMD_OPEN-related buffers
 185          *
 186          * It looks like a lot of different fields, but the trick is that
 187          * the only operation that happens often is the signalled pipes array
 188          * manipulation. That's why it's OK for now to keep the rest of the
 189          * fields under the same lock. If we notice too much contention because
 190          * of PIPE_CMD_OPEN, then we should add a separate lock there.
 191          */
 192         spinlock_t lock;
 193 
 194         /*
 195          * Array of the pipes of |pipes_capacity| elements,
 196          * indexed by goldfish_pipe::id
 197          */
 198         struct goldfish_pipe **pipes;
 199         u32 pipes_capacity;
 200 
 201         /* Pointers to the buffers host uses for interaction with this driver */
 202         struct goldfish_pipe_dev_buffers *buffers;
 203 
 204         /* Head of a doubly linked list of signalled pipes */
 205         struct goldfish_pipe *first_signalled_pipe;
 206 
 207         /* ptr to platform device's device struct */
 208         struct device *pdev_dev;
 209 
 210         /* Some device-specific data */
 211         int irq;
 212         int version;
 213         unsigned char __iomem *base;
 214 
 215         /* an irq tasklet to run goldfish_interrupt_task */
 216         struct tasklet_struct irq_tasklet;
 217 
 218         struct miscdevice miscdev;
 219 };
 220 
 221 static int goldfish_pipe_cmd_locked(struct goldfish_pipe *pipe,
 222                                     enum PipeCmdCode cmd)
 223 {
 224         pipe->command_buffer->cmd = cmd;
 225         /* failure by default */
 226         pipe->command_buffer->status = PIPE_ERROR_INVAL;
 227         writel(pipe->id, pipe->dev->base + PIPE_REG_CMD);
 228         return pipe->command_buffer->status;
 229 }
 230 
 231 static int goldfish_pipe_cmd(struct goldfish_pipe *pipe, enum PipeCmdCode cmd)
 232 {
 233         int status;
 234 
 235         if (mutex_lock_interruptible(&pipe->lock))
 236                 return PIPE_ERROR_IO;
 237         status = goldfish_pipe_cmd_locked(pipe, cmd);
 238         mutex_unlock(&pipe->lock);
 239         return status;
 240 }
 241 
 242 /*
 243  * This function converts an error code returned by the emulator through
 244  * the PIPE_REG_STATUS i/o register into a valid negative errno value.
 245  */
 246 static int goldfish_pipe_error_convert(int status)
 247 {
 248         switch (status) {
 249         case PIPE_ERROR_AGAIN:
 250                 return -EAGAIN;
 251         case PIPE_ERROR_NOMEM:
 252                 return -ENOMEM;
 253         case PIPE_ERROR_IO:
 254                 return -EIO;
 255         default:
 256                 return -EINVAL;
 257         }
 258 }
 259 
 260 static int pin_user_pages(unsigned long first_page,
 261                           unsigned long last_page,
 262                           unsigned int last_page_size,
 263                           int is_write,
 264                           struct page *pages[MAX_BUFFERS_PER_COMMAND],
 265                           unsigned int *iter_last_page_size)
 266 {
 267         int ret;
 268         int requested_pages = ((last_page - first_page) >> PAGE_SHIFT) + 1;
 269 
 270         if (requested_pages > MAX_BUFFERS_PER_COMMAND) {
 271                 requested_pages = MAX_BUFFERS_PER_COMMAND;
 272                 *iter_last_page_size = PAGE_SIZE;
 273         } else {
 274                 *iter_last_page_size = last_page_size;
 275         }
 276 
 277         ret = get_user_pages_fast(first_page, requested_pages,
 278                                   !is_write ? FOLL_WRITE : 0,
 279                                   pages);
 280         if (ret <= 0)
 281                 return -EFAULT;
 282         if (ret < requested_pages)
 283                 *iter_last_page_size = PAGE_SIZE;
 284 
 285         return ret;
 286 }
 287 
 288 static void release_user_pages(struct page **pages, int pages_count,
 289                                int is_write, s32 consumed_size)
 290 {
 291         int i;
 292 
 293         for (i = 0; i < pages_count; i++) {
 294                 if (!is_write && consumed_size > 0)
 295                         set_page_dirty(pages[i]);
 296                 put_page(pages[i]);
 297         }
 298 }
 299 
 300 /* Populate the call parameters, merging adjacent pages together */
 301 static void populate_rw_params(struct page **pages,
 302                                int pages_count,
 303                                unsigned long address,
 304                                unsigned long address_end,
 305                                unsigned long first_page,
 306                                unsigned long last_page,
 307                                unsigned int iter_last_page_size,
 308                                int is_write,
 309                                struct goldfish_pipe_command *command)
 310 {
 311         /*
 312          * Process the first page separately - it's the only page that
 313          * needs special handling for its start address.
 314          */
 315         unsigned long xaddr = page_to_phys(pages[0]);
 316         unsigned long xaddr_prev = xaddr;
 317         int buffer_idx = 0;
 318         int i = 1;
 319         int size_on_page = first_page == last_page
 320                         ? (int)(address_end - address)
 321                         : (PAGE_SIZE - (address & ~PAGE_MASK));
 322         command->rw_params.ptrs[0] = (u64)(xaddr | (address & ~PAGE_MASK));
 323         command->rw_params.sizes[0] = size_on_page;
 324         for (; i < pages_count; ++i) {
 325                 xaddr = page_to_phys(pages[i]);
 326                 size_on_page = (i == pages_count - 1) ?
 327                         iter_last_page_size : PAGE_SIZE;
 328                 if (xaddr == xaddr_prev + PAGE_SIZE) {
 329                         command->rw_params.sizes[buffer_idx] += size_on_page;
 330                 } else {
 331                         ++buffer_idx;
 332                         command->rw_params.ptrs[buffer_idx] = (u64)xaddr;
 333                         command->rw_params.sizes[buffer_idx] = size_on_page;
 334                 }
 335                 xaddr_prev = xaddr;
 336         }
 337         command->rw_params.buffers_count = buffer_idx + 1;
 338 }
 339 
 340 static int transfer_max_buffers(struct goldfish_pipe *pipe,
 341                                 unsigned long address,
 342                                 unsigned long address_end,
 343                                 int is_write,
 344                                 unsigned long last_page,
 345                                 unsigned int last_page_size,
 346                                 s32 *consumed_size,
 347                                 int *status)
 348 {
 349         unsigned long first_page = address & PAGE_MASK;
 350         unsigned int iter_last_page_size;
 351         int pages_count;
 352 
 353         /* Serialize access to the pipe command buffers */
 354         if (mutex_lock_interruptible(&pipe->lock))
 355                 return -ERESTARTSYS;
 356 
 357         pages_count = pin_user_pages(first_page, last_page,
 358                                      last_page_size, is_write,
 359                                      pipe->pages, &iter_last_page_size);
 360         if (pages_count < 0) {
 361                 mutex_unlock(&pipe->lock);
 362                 return pages_count;
 363         }
 364 
 365         populate_rw_params(pipe->pages, pages_count, address, address_end,
 366                            first_page, last_page, iter_last_page_size, is_write,
 367                            pipe->command_buffer);
 368 
 369         /* Transfer the data */
 370         *status = goldfish_pipe_cmd_locked(pipe,
 371                                 is_write ? PIPE_CMD_WRITE : PIPE_CMD_READ);
 372 
 373         *consumed_size = pipe->command_buffer->rw_params.consumed_size;
 374 
 375         release_user_pages(pipe->pages, pages_count, is_write, *consumed_size);
 376 
 377         mutex_unlock(&pipe->lock);
 378         return 0;
 379 }
 380 
 381 static int wait_for_host_signal(struct goldfish_pipe *pipe, int is_write)
 382 {
 383         u32 wake_bit = is_write ? BIT_WAKE_ON_WRITE : BIT_WAKE_ON_READ;
 384 
 385         set_bit(wake_bit, &pipe->flags);
 386 
 387         /* Tell the emulator we're going to wait for a wake event */
 388         goldfish_pipe_cmd(pipe,
 389                 is_write ? PIPE_CMD_WAKE_ON_WRITE : PIPE_CMD_WAKE_ON_READ);
 390 
 391         while (test_bit(wake_bit, &pipe->flags)) {
 392                 if (wait_event_interruptible(pipe->wake_queue,
 393                                              !test_bit(wake_bit, &pipe->flags)))
 394                         return -ERESTARTSYS;
 395 
 396                 if (test_bit(BIT_CLOSED_ON_HOST, &pipe->flags))
 397                         return -EIO;
 398         }
 399 
 400         return 0;
 401 }
 402 
 403 static ssize_t goldfish_pipe_read_write(struct file *filp,
 404                                         char __user *buffer,
 405                                         size_t bufflen,
 406                                         int is_write)
 407 {
 408         struct goldfish_pipe *pipe = filp->private_data;
 409         int count = 0, ret = -EINVAL;
 410         unsigned long address, address_end, last_page;
 411         unsigned int last_page_size;
 412 
 413         /* If the emulator already closed the pipe, no need to go further */
 414         if (unlikely(test_bit(BIT_CLOSED_ON_HOST, &pipe->flags)))
 415                 return -EIO;
 416         /* Null reads or writes succeeds */
 417         if (unlikely(bufflen == 0))
 418                 return 0;
 419         /* Check the buffer range for access */
 420         if (unlikely(!access_ok(buffer, bufflen)))
 421                 return -EFAULT;
 422 
 423         address = (unsigned long)buffer;
 424         address_end = address + bufflen;
 425         last_page = (address_end - 1) & PAGE_MASK;
 426         last_page_size = ((address_end - 1) & ~PAGE_MASK) + 1;
 427 
 428         while (address < address_end) {
 429                 s32 consumed_size;
 430                 int status;
 431 
 432                 ret = transfer_max_buffers(pipe, address, address_end, is_write,
 433                                            last_page, last_page_size,
 434                                            &consumed_size, &status);
 435                 if (ret < 0)
 436                         break;
 437 
 438                 if (consumed_size > 0) {
 439                         /* No matter what's the status, we've transferred
 440                          * something.
 441                          */
 442                         count += consumed_size;
 443                         address += consumed_size;
 444                 }
 445                 if (status > 0)
 446                         continue;
 447                 if (status == 0) {
 448                         /* EOF */
 449                         ret = 0;
 450                         break;
 451                 }
 452                 if (count > 0) {
 453                         /*
 454                          * An error occurred, but we already transferred
 455                          * something on one of the previous iterations.
 456                          * Just return what we already copied and log this
 457                          * err.
 458                          */
 459                         if (status != PIPE_ERROR_AGAIN)
 460                                 dev_err_ratelimited(pipe->dev->pdev_dev,
 461                                         "backend error %d on %s\n",
 462                                         status, is_write ? "write" : "read");
 463                         break;
 464                 }
 465 
 466                 /*
 467                  * If the error is not PIPE_ERROR_AGAIN, or if we are in
 468                  * non-blocking mode, just return the error code.
 469                  */
 470                 if (status != PIPE_ERROR_AGAIN ||
 471                         (filp->f_flags & O_NONBLOCK) != 0) {
 472                         ret = goldfish_pipe_error_convert(status);
 473                         break;
 474                 }
 475 
 476                 status = wait_for_host_signal(pipe, is_write);
 477                 if (status < 0)
 478                         return status;
 479         }
 480 
 481         if (count > 0)
 482                 return count;
 483         return ret;
 484 }
 485 
 486 static ssize_t goldfish_pipe_read(struct file *filp, char __user *buffer,
 487                                   size_t bufflen, loff_t *ppos)
 488 {
 489         return goldfish_pipe_read_write(filp, buffer, bufflen,
 490                                         /* is_write */ 0);
 491 }
 492 
 493 static ssize_t goldfish_pipe_write(struct file *filp,
 494                                    const char __user *buffer, size_t bufflen,
 495                                    loff_t *ppos)
 496 {
 497         /* cast away the const */
 498         char __user *no_const_buffer = (char __user *)buffer;
 499 
 500         return goldfish_pipe_read_write(filp, no_const_buffer, bufflen,
 501                                         /* is_write */ 1);
 502 }
 503 
 504 static __poll_t goldfish_pipe_poll(struct file *filp, poll_table *wait)
 505 {
 506         struct goldfish_pipe *pipe = filp->private_data;
 507         __poll_t mask = 0;
 508         int status;
 509 
 510         poll_wait(filp, &pipe->wake_queue, wait);
 511 
 512         status = goldfish_pipe_cmd(pipe, PIPE_CMD_POLL);
 513         if (status < 0)
 514                 return -ERESTARTSYS;
 515 
 516         if (status & PIPE_POLL_IN)
 517                 mask |= EPOLLIN | EPOLLRDNORM;
 518         if (status & PIPE_POLL_OUT)
 519                 mask |= EPOLLOUT | EPOLLWRNORM;
 520         if (status & PIPE_POLL_HUP)
 521                 mask |= EPOLLHUP;
 522         if (test_bit(BIT_CLOSED_ON_HOST, &pipe->flags))
 523                 mask |= EPOLLERR;
 524 
 525         return mask;
 526 }
 527 
 528 static void signalled_pipes_add_locked(struct goldfish_pipe_dev *dev,
 529                                        u32 id, u32 flags)
 530 {
 531         struct goldfish_pipe *pipe;
 532 
 533         if (WARN_ON(id >= dev->pipes_capacity))
 534                 return;
 535 
 536         pipe = dev->pipes[id];
 537         if (!pipe)
 538                 return;
 539         pipe->signalled_flags |= flags;
 540 
 541         if (pipe->prev_signalled || pipe->next_signalled ||
 542                 dev->first_signalled_pipe == pipe)
 543                 return; /* already in the list */
 544         pipe->next_signalled = dev->first_signalled_pipe;
 545         if (dev->first_signalled_pipe)
 546                 dev->first_signalled_pipe->prev_signalled = pipe;
 547         dev->first_signalled_pipe = pipe;
 548 }
 549 
 550 static void signalled_pipes_remove_locked(struct goldfish_pipe_dev *dev,
 551                                           struct goldfish_pipe *pipe)
 552 {
 553         if (pipe->prev_signalled)
 554                 pipe->prev_signalled->next_signalled = pipe->next_signalled;
 555         if (pipe->next_signalled)
 556                 pipe->next_signalled->prev_signalled = pipe->prev_signalled;
 557         if (pipe == dev->first_signalled_pipe)
 558                 dev->first_signalled_pipe = pipe->next_signalled;
 559         pipe->prev_signalled = NULL;
 560         pipe->next_signalled = NULL;
 561 }
 562 
 563 static struct goldfish_pipe *signalled_pipes_pop_front(
 564                 struct goldfish_pipe_dev *dev, int *wakes)
 565 {
 566         struct goldfish_pipe *pipe;
 567         unsigned long flags;
 568 
 569         spin_lock_irqsave(&dev->lock, flags);
 570 
 571         pipe = dev->first_signalled_pipe;
 572         if (pipe) {
 573                 *wakes = pipe->signalled_flags;
 574                 pipe->signalled_flags = 0;
 575                 /*
 576                  * This is an optimized version of
 577                  * signalled_pipes_remove_locked()
 578                  * - We want to make it as fast as possible to
 579                  * wake the sleeping pipe operations faster.
 580                  */
 581                 dev->first_signalled_pipe = pipe->next_signalled;
 582                 if (dev->first_signalled_pipe)
 583                         dev->first_signalled_pipe->prev_signalled = NULL;
 584                 pipe->next_signalled = NULL;
 585         }
 586 
 587         spin_unlock_irqrestore(&dev->lock, flags);
 588         return pipe;
 589 }
 590 
 591 static void goldfish_interrupt_task(unsigned long dev_addr)
 592 {
 593         /* Iterate over the signalled pipes and wake them one by one */
 594         struct goldfish_pipe_dev *dev = (struct goldfish_pipe_dev *)dev_addr;
 595         struct goldfish_pipe *pipe;
 596         int wakes;
 597 
 598         while ((pipe = signalled_pipes_pop_front(dev, &wakes)) != NULL) {
 599                 if (wakes & PIPE_WAKE_CLOSED) {
 600                         pipe->flags = 1 << BIT_CLOSED_ON_HOST;
 601                 } else {
 602                         if (wakes & PIPE_WAKE_READ)
 603                                 clear_bit(BIT_WAKE_ON_READ, &pipe->flags);
 604                         if (wakes & PIPE_WAKE_WRITE)
 605                                 clear_bit(BIT_WAKE_ON_WRITE, &pipe->flags);
 606                 }
 607                 /*
 608                  * wake_up_interruptible() implies a write barrier, so don't
 609                  * explicitly add another one here.
 610                  */
 611                 wake_up_interruptible(&pipe->wake_queue);
 612         }
 613 }
 614 
 615 static void goldfish_pipe_device_deinit(struct platform_device *pdev,
 616                                         struct goldfish_pipe_dev *dev);
 617 
 618 /*
 619  * The general idea of the interrupt handling:
 620  *
 621  *  1. device raises an interrupt if there's at least one signalled pipe
 622  *  2. IRQ handler reads the signalled pipes and their count from the device
 623  *  3. device writes them into a shared buffer and returns the count
 624  *      it only resets the IRQ if it has returned all signalled pipes,
 625  *      otherwise it leaves it raised, so IRQ handler will be called
 626  *      again for the next chunk
 627  *  4. IRQ handler adds all returned pipes to the device's signalled pipes list
 628  *  5. IRQ handler launches a tasklet to process the signalled pipes from the
 629  *      list in a separate context
 630  */
 631 static irqreturn_t goldfish_pipe_interrupt(int irq, void *dev_id)
 632 {
 633         u32 count;
 634         u32 i;
 635         unsigned long flags;
 636         struct goldfish_pipe_dev *dev = dev_id;
 637 
 638         if (dev->magic != &goldfish_pipe_device_deinit)
 639                 return IRQ_NONE;
 640 
 641         /* Request the signalled pipes from the device */
 642         spin_lock_irqsave(&dev->lock, flags);
 643 
 644         count = readl(dev->base + PIPE_REG_GET_SIGNALLED);
 645         if (count == 0) {
 646                 spin_unlock_irqrestore(&dev->lock, flags);
 647                 return IRQ_NONE;
 648         }
 649         if (count > MAX_SIGNALLED_PIPES)
 650                 count = MAX_SIGNALLED_PIPES;
 651 
 652         for (i = 0; i < count; ++i)
 653                 signalled_pipes_add_locked(dev,
 654                         dev->buffers->signalled_pipe_buffers[i].id,
 655                         dev->buffers->signalled_pipe_buffers[i].flags);
 656 
 657         spin_unlock_irqrestore(&dev->lock, flags);
 658 
 659         tasklet_schedule(&dev->irq_tasklet);
 660         return IRQ_HANDLED;
 661 }
 662 
 663 static int get_free_pipe_id_locked(struct goldfish_pipe_dev *dev)
 664 {
 665         int id;
 666 
 667         for (id = 0; id < dev->pipes_capacity; ++id)
 668                 if (!dev->pipes[id])
 669                         return id;
 670 
 671         {
 672                 /* Reallocate the array.
 673                  * Since get_free_pipe_id_locked runs with interrupts disabled,
 674                  * we don't want to make calls that could lead to sleep.
 675                  */
 676                 u32 new_capacity = 2 * dev->pipes_capacity;
 677                 struct goldfish_pipe **pipes =
 678                         kcalloc(new_capacity, sizeof(*pipes), GFP_ATOMIC);
 679                 if (!pipes)
 680                         return -ENOMEM;
 681                 memcpy(pipes, dev->pipes, sizeof(*pipes) * dev->pipes_capacity);
 682                 kfree(dev->pipes);
 683                 dev->pipes = pipes;
 684                 id = dev->pipes_capacity;
 685                 dev->pipes_capacity = new_capacity;
 686         }
 687         return id;
 688 }
 689 
 690 /* A helper function to get the instance of goldfish_pipe_dev from file */
 691 static struct goldfish_pipe_dev *to_goldfish_pipe_dev(struct file *file)
 692 {
 693         struct miscdevice *miscdev = file->private_data;
 694 
 695         return container_of(miscdev, struct goldfish_pipe_dev, miscdev);
 696 }
 697 
 698 /**
 699  *      goldfish_pipe_open - open a channel to the AVD
 700  *      @inode: inode of device
 701  *      @file: file struct of opener
 702  *
 703  *      Create a new pipe link between the emulator and the use application.
 704  *      Each new request produces a new pipe.
 705  *
 706  *      Note: we use the pipe ID as a mux. All goldfish emulations are 32bit
 707  *      right now so this is fine. A move to 64bit will need this addressing
 708  */
 709 static int goldfish_pipe_open(struct inode *inode, struct file *file)
 710 {
 711         struct goldfish_pipe_dev *dev = to_goldfish_pipe_dev(file);
 712         unsigned long flags;
 713         int id;
 714         int status;
 715 
 716         /* Allocate new pipe kernel object */
 717         struct goldfish_pipe *pipe = kzalloc(sizeof(*pipe), GFP_KERNEL);
 718 
 719         if (!pipe)
 720                 return -ENOMEM;
 721 
 722         pipe->dev = dev;
 723         mutex_init(&pipe->lock);
 724         init_waitqueue_head(&pipe->wake_queue);
 725 
 726         /*
 727          * Command buffer needs to be allocated on its own page to make sure
 728          * it is physically contiguous in host's address space.
 729          */
 730         BUILD_BUG_ON(sizeof(struct goldfish_pipe_command) > PAGE_SIZE);
 731         pipe->command_buffer =
 732                 (struct goldfish_pipe_command *)__get_free_page(GFP_KERNEL);
 733         if (!pipe->command_buffer) {
 734                 status = -ENOMEM;
 735                 goto err_pipe;
 736         }
 737 
 738         spin_lock_irqsave(&dev->lock, flags);
 739 
 740         id = get_free_pipe_id_locked(dev);
 741         if (id < 0) {
 742                 status = id;
 743                 goto err_id_locked;
 744         }
 745 
 746         dev->pipes[id] = pipe;
 747         pipe->id = id;
 748         pipe->command_buffer->id = id;
 749 
 750         /* Now tell the emulator we're opening a new pipe. */
 751         dev->buffers->open_command_params.rw_params_max_count =
 752                         MAX_BUFFERS_PER_COMMAND;
 753         dev->buffers->open_command_params.command_buffer_ptr =
 754                         (u64)(unsigned long)__pa(pipe->command_buffer);
 755         status = goldfish_pipe_cmd_locked(pipe, PIPE_CMD_OPEN);
 756         spin_unlock_irqrestore(&dev->lock, flags);
 757         if (status < 0)
 758                 goto err_cmd;
 759         /* All is done, save the pipe into the file's private data field */
 760         file->private_data = pipe;
 761         return 0;
 762 
 763 err_cmd:
 764         spin_lock_irqsave(&dev->lock, flags);
 765         dev->pipes[id] = NULL;
 766 err_id_locked:
 767         spin_unlock_irqrestore(&dev->lock, flags);
 768         free_page((unsigned long)pipe->command_buffer);
 769 err_pipe:
 770         kfree(pipe);
 771         return status;
 772 }
 773 
 774 static int goldfish_pipe_release(struct inode *inode, struct file *filp)
 775 {
 776         unsigned long flags;
 777         struct goldfish_pipe *pipe = filp->private_data;
 778         struct goldfish_pipe_dev *dev = pipe->dev;
 779 
 780         /* The guest is closing the channel, so tell the emulator right now */
 781         goldfish_pipe_cmd(pipe, PIPE_CMD_CLOSE);
 782 
 783         spin_lock_irqsave(&dev->lock, flags);
 784         dev->pipes[pipe->id] = NULL;
 785         signalled_pipes_remove_locked(dev, pipe);
 786         spin_unlock_irqrestore(&dev->lock, flags);
 787 
 788         filp->private_data = NULL;
 789         free_page((unsigned long)pipe->command_buffer);
 790         kfree(pipe);
 791         return 0;
 792 }
 793 
 794 static const struct file_operations goldfish_pipe_fops = {
 795         .owner = THIS_MODULE,
 796         .read = goldfish_pipe_read,
 797         .write = goldfish_pipe_write,
 798         .poll = goldfish_pipe_poll,
 799         .open = goldfish_pipe_open,
 800         .release = goldfish_pipe_release,
 801 };
 802 
 803 static void init_miscdevice(struct miscdevice *miscdev)
 804 {
 805         memset(miscdev, 0, sizeof(*miscdev));
 806 
 807         miscdev->minor = MISC_DYNAMIC_MINOR;
 808         miscdev->name = "goldfish_pipe";
 809         miscdev->fops = &goldfish_pipe_fops;
 810 }
 811 
 812 static void write_pa_addr(void *addr, void __iomem *portl, void __iomem *porth)
 813 {
 814         const unsigned long paddr = __pa(addr);
 815 
 816         writel(upper_32_bits(paddr), porth);
 817         writel(lower_32_bits(paddr), portl);
 818 }
 819 
 820 static int goldfish_pipe_device_init(struct platform_device *pdev,
 821                                      struct goldfish_pipe_dev *dev)
 822 {
 823         int err;
 824 
 825         tasklet_init(&dev->irq_tasklet, &goldfish_interrupt_task,
 826                      (unsigned long)dev);
 827 
 828         err = devm_request_irq(&pdev->dev, dev->irq,
 829                                goldfish_pipe_interrupt,
 830                                IRQF_SHARED, "goldfish_pipe", dev);
 831         if (err) {
 832                 dev_err(&pdev->dev, "unable to allocate IRQ for v2\n");
 833                 return err;
 834         }
 835 
 836         init_miscdevice(&dev->miscdev);
 837         err = misc_register(&dev->miscdev);
 838         if (err) {
 839                 dev_err(&pdev->dev, "unable to register v2 device\n");
 840                 return err;
 841         }
 842 
 843         dev->pdev_dev = &pdev->dev;
 844         dev->first_signalled_pipe = NULL;
 845         dev->pipes_capacity = INITIAL_PIPES_CAPACITY;
 846         dev->pipes = kcalloc(dev->pipes_capacity, sizeof(*dev->pipes),
 847                              GFP_KERNEL);
 848         if (!dev->pipes) {
 849                 misc_deregister(&dev->miscdev);
 850                 return -ENOMEM;
 851         }
 852 
 853         /*
 854          * We're going to pass two buffers, open_command_params and
 855          * signalled_pipe_buffers, to the host. This means each of those buffers
 856          * needs to be contained in a single physical page. The easiest choice
 857          * is to just allocate a page and place the buffers in it.
 858          */
 859         BUILD_BUG_ON(sizeof(struct goldfish_pipe_dev_buffers) > PAGE_SIZE);
 860         dev->buffers = (struct goldfish_pipe_dev_buffers *)
 861                 __get_free_page(GFP_KERNEL);
 862         if (!dev->buffers) {
 863                 kfree(dev->pipes);
 864                 misc_deregister(&dev->miscdev);
 865                 return -ENOMEM;
 866         }
 867 
 868         /* Send the buffer addresses to the host */
 869         write_pa_addr(&dev->buffers->signalled_pipe_buffers,
 870                       dev->base + PIPE_REG_SIGNAL_BUFFER,
 871                       dev->base + PIPE_REG_SIGNAL_BUFFER_HIGH);
 872 
 873         writel(MAX_SIGNALLED_PIPES,
 874                dev->base + PIPE_REG_SIGNAL_BUFFER_COUNT);
 875 
 876         write_pa_addr(&dev->buffers->open_command_params,
 877                       dev->base + PIPE_REG_OPEN_BUFFER,
 878                       dev->base + PIPE_REG_OPEN_BUFFER_HIGH);
 879 
 880         platform_set_drvdata(pdev, dev);
 881         return 0;
 882 }
 883 
 884 static void goldfish_pipe_device_deinit(struct platform_device *pdev,
 885                                         struct goldfish_pipe_dev *dev)
 886 {
 887         misc_deregister(&dev->miscdev);
 888         tasklet_kill(&dev->irq_tasklet);
 889         kfree(dev->pipes);
 890         free_page((unsigned long)dev->buffers);
 891 }
 892 
 893 static int goldfish_pipe_probe(struct platform_device *pdev)
 894 {
 895         struct resource *r;
 896         struct goldfish_pipe_dev *dev;
 897 
 898         dev = devm_kzalloc(&pdev->dev, sizeof(*dev), GFP_KERNEL);
 899         if (!dev)
 900                 return -ENOMEM;
 901 
 902         dev->magic = &goldfish_pipe_device_deinit;
 903         spin_lock_init(&dev->lock);
 904 
 905         r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 906         if (!r || resource_size(r) < PAGE_SIZE) {
 907                 dev_err(&pdev->dev, "can't allocate i/o page\n");
 908                 return -EINVAL;
 909         }
 910         dev->base = devm_ioremap(&pdev->dev, r->start, PAGE_SIZE);
 911         if (!dev->base) {
 912                 dev_err(&pdev->dev, "ioremap failed\n");
 913                 return -EINVAL;
 914         }
 915 
 916         r = platform_get_resource(pdev, IORESOURCE_IRQ, 0);
 917         if (!r)
 918                 return -EINVAL;
 919 
 920         dev->irq = r->start;
 921 
 922         /*
 923          * Exchange the versions with the host device
 924          *
 925          * Note: v1 driver used to not report its version, so we write it before
 926          *  reading device version back: this allows the host implementation to
 927          *  detect the old driver (if there was no version write before read).
 928          */
 929         writel(PIPE_DRIVER_VERSION, dev->base + PIPE_REG_VERSION);
 930         dev->version = readl(dev->base + PIPE_REG_VERSION);
 931         if (WARN_ON(dev->version < PIPE_CURRENT_DEVICE_VERSION))
 932                 return -EINVAL;
 933 
 934         return goldfish_pipe_device_init(pdev, dev);
 935 }
 936 
 937 static int goldfish_pipe_remove(struct platform_device *pdev)
 938 {
 939         struct goldfish_pipe_dev *dev = platform_get_drvdata(pdev);
 940 
 941         goldfish_pipe_device_deinit(pdev, dev);
 942         return 0;
 943 }
 944 
 945 static const struct acpi_device_id goldfish_pipe_acpi_match[] = {
 946         { "GFSH0003", 0 },
 947         { },
 948 };
 949 MODULE_DEVICE_TABLE(acpi, goldfish_pipe_acpi_match);
 950 
 951 static const struct of_device_id goldfish_pipe_of_match[] = {
 952         { .compatible = "google,android-pipe", },
 953         {},
 954 };
 955 MODULE_DEVICE_TABLE(of, goldfish_pipe_of_match);
 956 
 957 static struct platform_driver goldfish_pipe_driver = {
 958         .probe = goldfish_pipe_probe,
 959         .remove = goldfish_pipe_remove,
 960         .driver = {
 961                 .name = "goldfish_pipe",
 962                 .of_match_table = goldfish_pipe_of_match,
 963                 .acpi_match_table = ACPI_PTR(goldfish_pipe_acpi_match),
 964         }
 965 };
 966 
 967 module_platform_driver(goldfish_pipe_driver);
 968 MODULE_AUTHOR("David Turner <digit@google.com>");
 969 MODULE_LICENSE("GPL v2");