device: allow to use dummy as a way to test streamer

This adds loopback tests via `tests/`

device/dummy/buffer.c

@@ -1,11 +1,18 @@
 #include "dummy.h"
 #include "device/buffer.h"
+#include "device/buffer_list.h"
+#include "util/opts/log.h"
 
 #include <stdlib.h>
+#include <sys/types.h>
+#include <sys/stat.h>
 
 int dummy_buffer_open(buffer_t *buf)
 {
   buf->dummy = calloc(1, sizeof(buffer_dummy_t));
+  buf->start = buf->buf_list->dummy->data;
+  buf->used = buf->buf_list->dummy->length;
+  buf->length = buf->buf_list->dummy->length;
   return 0;
 }
 
@@ -16,15 +23,39 @@ void dummy_buffer_close(buffer_t *buf)
 
 int dummy_buffer_enqueue(buffer_t *buf, const char *who)
 {
-  return -1;
+  unsigned index = buf->index;
+  if (write(buf->buf_list->dummy->fds[1], &index, sizeof(index)) != sizeof(index)) {
+    return -1;
+  }
+  return 0;
 }
 
 int dummy_buffer_list_dequeue(buffer_list_t *buf_list, buffer_t **bufp)
 {
-  return -1;
+  unsigned index = 0;
+  int n = read(buf_list->dummy->fds[0], &index, sizeof(index));
+  if (n != sizeof(index)) {
+    LOG_INFO(buf_list, "Received invalid result from `read`: %d", n);
+    return -1;
+  }
+
+  if (index >= (unsigned)buf_list->nbufs) {
+    LOG_INFO(buf_list, "Received invalid index from `read`: %d >= %d", index, buf_list->nbufs);
+    return -1;
+  }
+
+  *bufp = buf_list->bufs[index];
+  return 0;
 }
 
 int dummy_buffer_list_pollfd(buffer_list_t *buf_list, struct pollfd *pollfd, bool can_dequeue)
 {
-  return -1;
+  int count_enqueued = buffer_list_count_enqueued(buf_list);
+  pollfd->fd = buf_list->dummy->fds[0]; // write end
+  pollfd->events = POLLHUP;
+  if (can_dequeue && count_enqueued > 0) {
+    pollfd->events |= POLLIN;
+  }
+  pollfd->revents = 0;
+  return 0;
 }

device/dummy/buffer_list.c

@@ -1,25 +1,69 @@
 #include "dummy.h"
 #include "device/buffer_list.h"
+#include "device/device.h"
+#include "util/opts/log.h"
 
 #include <stdlib.h>
+#include <sys/types.h>
+#include <sys/stat.h>
 
 int dummy_buffer_list_open(buffer_list_t *buf_list)
 {
+  int fd = -1;
+
   buf_list->dummy = calloc(1, sizeof(buffer_list_dummy_t));
-  return 0;
+  buf_list->dummy->fds[0] = -1;
+  buf_list->dummy->fds[1] = -1;
+
+  if (!buf_list->do_capture) {
+    LOG_ERROR(buf_list, "Only capture mode supported");
+  }
+
+  if (pipe2(buf_list->dummy->fds, O_DIRECT|O_CLOEXEC) < 0) {
+    LOG_INFO(buf_list, "Cannot open `pipe2`.");
+    return -1;
+  }
+
+  fd = open(buf_list->dev->path, O_RDWR|O_NONBLOCK);
+  if (fd < 0) {
+		LOG_ERROR(buf_list, "Can't open device: %s", buf_list->dev->path);
+  }
+
+  struct stat st;
+  if (fstat(fd, &st) < 0) {
+		LOG_ERROR(buf_list, "Can't get fstat: %s", buf_list->dev->path);
+  }
+
+  buf_list->dummy->data = malloc(st.st_size);
+  if (!buf_list->dummy->data) {
+		LOG_ERROR(buf_list, "Can't allocate %ld bytes for %s", st.st_size, buf_list->dev->path);
+  }
+
+  buf_list->dummy->length = read(fd, buf_list->dummy->data, st.st_size);
+  if (!buf_list->dummy->data) {
+		LOG_ERROR(buf_list, "Can't read %ld bytes for %s. Only read %zu.", st.st_size, buf_list->dev->path, buf_list->dummy->length);
+  }
+
+  close(fd);
+  return buf_list->fmt.nbufs;
+
+error:
+  close(fd);
+  return -1;
 }
 
 void dummy_buffer_list_close(buffer_list_t *buf_list)
 {
-  free(buf_list->dummy);
-}
+  if (buf_list->dummy) {
+    close(buf_list->dummy->fds[0]);
+    close(buf_list->dummy->fds[1]);
+    free(buf_list->dummy->data);
+  }
 
-int dummy_buffer_list_set_buffers(buffer_list_t *buf_list, int nbufs)
-{
-  return -1;
+  free(buf_list->dummy);
 }
 
 int dummy_buffer_list_set_stream(buffer_list_t *buf_list, bool do_on)
 {
-  return -1;
+  return 0;
 }

device/dummy/device.c

@@ -5,6 +5,7 @@
 
 int dummy_device_open(device_t *dev)
 {
+  dev->opts.allow_dma = false;
   dev->dummy = calloc(1, sizeof(device_dummy_t));
   return 0;
 }

device/dummy/dummy.h

@@ -2,6 +2,7 @@
 
 #include <stdbool.h>
 #include <stdint.h>
+#include <unistd.h>
 
 typedef struct buffer_s buffer_t;
 typedef struct buffer_list_s buffer_list_t;
@@ -12,6 +13,9 @@ typedef struct device_dummy_s {
 } device_dummy_t;
 
 typedef struct buffer_list_dummy_s {
+  int fds[2];
+  void *data;
+  size_t length;
 } buffer_list_dummy_t;
 
 typedef struct buffer_dummy_s {
@@ -32,5 +36,4 @@ int dummy_buffer_list_pollfd(buffer_list_t *buf_list, struct pollfd *pollfd, boo
 
 int dummy_buffer_list_open(buffer_list_t *buf_list);
 void dummy_buffer_list_close(buffer_list_t *buf_list);
-int dummy_buffer_list_set_buffers(buffer_list_t *buf_list, int nbufs);
 int dummy_buffer_list_set_stream(buffer_list_t *buf_list, bool do_on);