| // Copyright 2018 The Fuchsia Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| #include <stdio.h> |
| #include <stdlib.h> |
| #include <string.h> |
| #include <threads.h> |
| #include <zircon/syscalls.h> |
| #include <zircon/types.h> |
| |
| #include <ddk/binding.h> |
| #include <ddk/device.h> |
| #include <ddk/driver.h> |
| |
| // fifo must be a power of 2 for the math to work |
| #define FIFOSIZE 32768 |
| #define FIFOMASK (FIFOSIZE - 1) |
| |
| typedef struct { |
| zx_device_t* zxdev; |
| mtx_t lock; |
| uint32_t head; |
| uint32_t tail; |
| char data[FIFOSIZE]; |
| } fifodev_t; |
| |
| static size_t fifo_readable(fifodev_t* fifo) { return (fifo->head - fifo->tail) & FIFOMASK; } |
| |
| static size_t fifo_writable(fifodev_t* fifo) { |
| return FIFOMASK - ((fifo->head - fifo->tail) & FIFOMASK); |
| } |
| |
| static size_t fifo_put(fifodev_t* fifo, const void* buf, size_t len) { |
| size_t count = fifo_writable(fifo); |
| uint32_t pos = fifo->head & FIFOMASK; |
| size_t space = FIFOSIZE - pos; |
| if (count > space) { // don't wrap around (single copy) |
| count = space; |
| } |
| if (count > len) { // limit to requested count |
| count = len; |
| } |
| memcpy(fifo->data + pos, buf, count); |
| fifo->head += count; |
| return count; |
| } |
| |
| static size_t fifo_get(fifodev_t* fifo, void* buf, size_t len) { |
| size_t count = fifo_readable(fifo); |
| uint32_t pos = fifo->tail & FIFOMASK; |
| size_t space = FIFOSIZE - pos; |
| if (count > space) { // don't wrap around (single copy) |
| count = space; |
| } |
| if (count > len) { // limit to requested count |
| count = len; |
| } |
| memcpy(buf, fifo->data + pos, count); |
| fifo->tail += count; |
| return count; |
| } |
| |
| static zx_status_t fifo_read(void* ctx, void* buf, size_t len, zx_off_t off, size_t* actual) { |
| fifodev_t* fifo = ctx; |
| |
| mtx_lock(&fifo->lock); |
| size_t n = 0; |
| size_t count; |
| while ((count = fifo_get(fifo, buf, len)) > 0) { |
| len -= count; |
| buf += count; |
| n += count; |
| } |
| if (n == 0) { |
| device_state_clr(fifo->zxdev, DEV_STATE_READABLE); |
| } else { |
| device_state_set(fifo->zxdev, DEV_STATE_WRITABLE); |
| } |
| mtx_unlock(&fifo->lock); |
| *actual = n; |
| |
| return (n == 0) ? ZX_ERR_SHOULD_WAIT : ZX_OK; |
| } |
| |
| static zx_status_t fifo_write(void* ctx, const void* buf, size_t len, zx_off_t off, |
| size_t* actual) { |
| fifodev_t* fifo = ctx; |
| |
| mtx_lock(&fifo->lock); |
| size_t n = 0; |
| size_t count; |
| while ((count = fifo_put(fifo, buf, len)) > 0) { |
| len -= count; |
| buf += count; |
| n += count; |
| } |
| if (n == 0) { |
| device_state_clr(fifo->zxdev, DEV_STATE_WRITABLE); |
| } else { |
| device_state_set(fifo->zxdev, DEV_STATE_READABLE); |
| } |
| mtx_unlock(&fifo->lock); |
| *actual = n; |
| |
| return (n == 0) ? ZX_ERR_SHOULD_WAIT : ZX_OK; |
| } |
| |
| static void fifo_release(void* ctx) { |
| fifodev_t* fifo = ctx; |
| free(fifo); |
| } |
| |
| static zx_protocol_device_t fifo_ops = { |
| .version = DEVICE_OPS_VERSION, |
| .read = fifo_read, |
| .write = fifo_write, |
| .release = fifo_release, |
| }; |
| |
| static zx_status_t fifo_bind(void* ctx, zx_device_t* parent) { |
| fifodev_t* fifo = calloc(1, sizeof(fifodev_t)); |
| if (fifo == NULL) { |
| return ZX_ERR_NO_MEMORY; |
| } |
| mtx_init(&fifo->lock, mtx_plain); |
| |
| device_add_args_t args = { |
| .version = DEVICE_ADD_ARGS_VERSION, |
| .name = "demo-fifo", |
| .ctx = fifo, |
| .ops = &fifo_ops, |
| }; |
| zx_status_t status = device_add(parent, &args, &fifo->zxdev); |
| if (status != ZX_OK) { |
| free(fifo); |
| return status; |
| } |
| |
| // initially we're empty, so writable but not readable |
| device_state_set(fifo->zxdev, DEV_STATE_WRITABLE); |
| |
| return ZX_OK; |
| } |
| |
| static zx_driver_ops_t fifo_driver_ops = { |
| .version = DRIVER_OPS_VERSION, |
| .bind = fifo_bind, |
| }; |
| |
| // clang-format off |
| ZIRCON_DRIVER_BEGIN(demo_fifo, fifo_driver_ops, "zircon", "0.1", 1) |
| BI_MATCH_IF(EQ, BIND_PROTOCOL, ZX_PROTOCOL_MISC_PARENT), |
| ZIRCON_DRIVER_END(demo_fifo) |
| // clang-format on |