There're several types of system calls for multiplexed I/O. They're used to receive notifications of I/O events. Typically, userspace applications call them against file descriptor to yield CPU. When I/O is enabled on any of the descriptors, process of the application is rescheduled, then the application execute I/O calls.
This commit adds a common interface for this type of system calls, named as 'waiter'. This is expected to be used with non-blocking file operation and operations on mapped page frame.
Signed-off-by: Takashi Sakamoto o-takashi@sakamocchi.jp --- axfer/Makefile.am | 7 ++++-- axfer/waiter.c | 66 +++++++++++++++++++++++++++++++++++++++++++++++++++++++ axfer/waiter.h | 45 +++++++++++++++++++++++++++++++++++++ 3 files changed, 116 insertions(+), 2 deletions(-) create mode 100644 axfer/waiter.c create mode 100644 axfer/waiter.h
diff --git a/axfer/Makefile.am b/axfer/Makefile.am index b378442b..f290cca8 100644 --- a/axfer/Makefile.am +++ b/axfer/Makefile.am @@ -21,7 +21,8 @@ noinst_HEADERS = \ mapper.h options.h \ xfer.h \ - xfer-alsa.h + xfer-alsa.h \ + waiter.h
axfer_SOURCES = \ misc.h \ @@ -45,4 +46,6 @@ axfer_SOURCES = \ xfer-libasound.h \ xfer-libasound.c \ xfer-libasound-irq-rw.c \ - subcmd-transfer.c + subcmd-transfer.c \ + waiter.h \ + waiter.c diff --git a/axfer/waiter.c b/axfer/waiter.c new file mode 100644 index 00000000..dfe42f84 --- /dev/null +++ b/axfer/waiter.c @@ -0,0 +1,66 @@ +/* + * waiter.c - I/O event waiter. + * + * Copyright (c) 2017 Takashi Sakamoto o-takashi@sakamocchi.jp + * + * Licensed under the terms of the GNU General Public License, version 2. + */ + +#include "waiter.h" + +#include <stdlib.h> +#include <string.h> +#include <errno.h> + +#include "misc.h" + +int waiter_context_init(struct waiter_context *waiter, enum waiter_type type) +{ + struct { + enum waiter_type type; + const struct waiter_data *waiter; + } entries[] = { + {WAITER_TYPE_COUNT, NULL}, + }; + int i; + + for (i = 0; i < ARRAY_SIZE(entries); ++i) { + if (entries[i].type == type) + break; + } + if (i == ARRAY_SIZE(entries)) + return -EINVAL; + + waiter->private_data = malloc(entries[i].waiter->private_size); + if (waiter->private_data == NULL) + return -ENOMEM; + memset(waiter->private_data, 0, entries[i].waiter->private_size); + + waiter->type = type; + waiter->ops = &entries[i].waiter->ops; + + return 0; +} + +int waiter_context_prepare(struct waiter_context *waiter, int *fds, + unsigned int fd_count) +{ + return waiter->ops->prepare(waiter, fds, fd_count); +} + +int waiter_context_wait_event(struct waiter_context *waiter, int timeout_msec) +{ + return waiter->ops->wait_event(waiter, timeout_msec); +} + +void waiter_context_release(struct waiter_context *waiter) +{ + waiter->ops->release(waiter); +} + +void waiter_context_destroy(struct waiter_context *waiter) +{ + if (waiter->private_data) + free(waiter->private_data); + waiter->private_data = NULL; +} diff --git a/axfer/waiter.h b/axfer/waiter.h new file mode 100644 index 00000000..dbd7ca70 --- /dev/null +++ b/axfer/waiter.h @@ -0,0 +1,45 @@ +/* + * waiter.h - a header for I/O event waiter. + * + * Copyright (c) 2017 Takashi Sakamoto o-takashi@sakamocchi.jp + * + * Licensed under the terms of the GNU General Public License, version 2. + */ + +#ifndef __ALSA_UTILS_AXFER_WAITER__H_ +#define __ALSA_UTILS_AXFER_WAITER__H_ + +enum waiter_type { + WAITER_TYPE_COUNT, +}; + +struct waiter_ops; + +struct waiter_context { + enum waiter_type type; + const struct waiter_ops *ops; + void *private_data; +}; + +int waiter_context_init(struct waiter_context *waiter, enum waiter_type type); +int waiter_context_prepare(struct waiter_context *waiter, int *fds, + unsigned int fd_count); +int waiter_context_wait_event(struct waiter_context *waiter, int timeout_msec); +void waiter_context_release(struct waiter_context *waiter); +void waiter_context_destroy(struct waiter_context *waiter); + +/* For internal use in 'waiter' module. */ + +struct waiter_ops { + int (*prepare)(struct waiter_context *waiter, int *fds, + unsigned int fd_count); + int (*wait_event)(struct waiter_context *waiter, int timeout_msec); + void (*release)(struct waiter_context *waiter); +}; + +struct waiter_data { + struct waiter_ops ops; + unsigned int private_size; +}; + +#endif