tools/usb/ffs-aio-example/simple/device_app/aio_simple.c - linux - Git at Google

 /*
  * This is free and unencumbered software released into the public domain.
  *
  * Anyone is free to copy, modify, publish, use, compile, sell, or
  * distribute this software, either in source code form or as a compiled
  * binary, for any purpose, commercial or non-commercial, and by any
  * means.
  *
  * In jurisdictions that recognize copyright laws, the author or authors
  * of this software dedicate any and all copyright interest in the
  * software to the public domain. We make this dedication for the benefit
  * of the public at large and to the detriment of our heirs and
  * successors. We intend this dedication to be an overt act of
  * relinquishment in perpetuity of all present and future rights to this
  * software under copyright law.
  *
  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
  * IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR
  * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
  * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
  * OTHER DEALINGS IN THE SOFTWARE.
  *
  * For more information, please refer to <http://unlicense.org/>
  */

 /* $(CROSS_COMPILE)cc -g -o aio_simple aio_simple.c -laio */

 #define _DEFAULT_SOURCE /* for endian.h */

 #include <endian.h>
 #include <errno.h>
 #include <fcntl.h>
 #include <stdarg.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <sys/ioctl.h>
 #include <sys/stat.h>
 #include <sys/types.h>
 #include <sys/poll.h>
 #include <unistd.h>
 #include <stdbool.h>
 #include <sys/eventfd.h>

 #include "libaio.h"
 #define IOCB_FLAG_RESFD         (1 << 0)

 #include <linux/usb/functionfs.h>

 #define BUF_LEN		8192

 /*
  * cpu_to_le16/32 are used when initializing structures, a context where a
  * function call is not allowed. To solve this, we code cpu_to_le16/32 in a way
  * that allows them to be used when initializing structures.
  */

 #if BYTE_ORDER == __LITTLE_ENDIAN
 #define cpu_to_le16(x)  (x)
 #define cpu_to_le32(x)  (x)
 #else
 #define cpu_to_le16(x)  ((((x) >> 8) & 0xffu) | (((x) & 0xffu) << 8))
 #define cpu_to_le32(x)  \
 	((((x) & 0xff000000u) >> 24) | (((x) & 0x00ff0000u) >>  8) | \
 	(((x) & 0x0000ff00u) <<  8) | (((x) & 0x000000ffu) << 24))
 #endif

 /******************** Descriptors and Strings *******************************/

 static const struct {
 	struct usb_functionfs_descs_head_v2 header;
 	__le32 fs_count;
 	__le32 hs_count;
 	struct {
 		struct usb_interface_descriptor intf;
 		struct usb_endpoint_descriptor_no_audio bulk_sink;
 		struct usb_endpoint_descriptor_no_audio bulk_source;
 	} __attribute__ ((__packed__)) fs_descs, hs_descs;
 } __attribute__ ((__packed__)) descriptors = {
 	.header = {
 		.magic = cpu_to_le32(FUNCTIONFS_DESCRIPTORS_MAGIC_V2),
 		.flags = cpu_to_le32(FUNCTIONFS_HAS_FS_DESC |
 				     FUNCTIONFS_HAS_HS_DESC),
 		.length = cpu_to_le32(sizeof(descriptors)),
 	},
 	.fs_count = cpu_to_le32(3),
 	.fs_descs = {
 		.intf = {
 			.bLength = sizeof(descriptors.fs_descs.intf),
 			.bDescriptorType = USB_DT_INTERFACE,
 			.bNumEndpoints = 2,
 			.bInterfaceClass = USB_CLASS_VENDOR_SPEC,
 			.iInterface = 1,
 		},
 		.bulk_sink = {
 			.bLength = sizeof(descriptors.fs_descs.bulk_sink),
 			.bDescriptorType = USB_DT_ENDPOINT,
 			.bEndpointAddress = 1 | USB_DIR_IN,
 			.bmAttributes = USB_ENDPOINT_XFER_BULK,
 		},
 		.bulk_source = {
 			.bLength = sizeof(descriptors.fs_descs.bulk_source),
 			.bDescriptorType = USB_DT_ENDPOINT,
 			.bEndpointAddress = 2 | USB_DIR_OUT,
 			.bmAttributes = USB_ENDPOINT_XFER_BULK,
 		},
 	},
 	.hs_count = cpu_to_le32(3),
 	.hs_descs = {
 		.intf = {
 			.bLength = sizeof(descriptors.hs_descs.intf),
 			.bDescriptorType = USB_DT_INTERFACE,
 			.bNumEndpoints = 2,
 			.bInterfaceClass = USB_CLASS_VENDOR_SPEC,
 			.iInterface = 1,
 		},
 		.bulk_sink = {
 			.bLength = sizeof(descriptors.hs_descs.bulk_sink),
 			.bDescriptorType = USB_DT_ENDPOINT,
 			.bEndpointAddress = 1 | USB_DIR_IN,
 			.bmAttributes = USB_ENDPOINT_XFER_BULK,
 			.wMaxPacketSize = cpu_to_le16(512),
 		},
 		.bulk_source = {
 			.bLength = sizeof(descriptors.hs_descs.bulk_source),
 			.bDescriptorType = USB_DT_ENDPOINT,
 			.bEndpointAddress = 2 | USB_DIR_OUT,
 			.bmAttributes = USB_ENDPOINT_XFER_BULK,
 			.wMaxPacketSize = cpu_to_le16(512),
 		},
 	},
 };

 #define STR_INTERFACE "AIO Test"

 static const struct {
 	struct usb_functionfs_strings_head header;
 	struct {
 		__le16 code;
 		const char str1[sizeof(STR_INTERFACE)];
 	} __attribute__ ((__packed__)) lang0;
 } __attribute__ ((__packed__)) strings = {
 	.header = {
 		.magic = cpu_to_le32(FUNCTIONFS_STRINGS_MAGIC),
 		.length = cpu_to_le32(sizeof(strings)),
 		.str_count = cpu_to_le32(1),
 		.lang_count = cpu_to_le32(1),
 	},
 	.lang0 = {
 		cpu_to_le16(0x0409), /* en-us */
 		STR_INTERFACE,
 	},
 };

 /******************** Endpoints handling *******************************/

 static void display_event(struct usb_functionfs_event *event)
 {
 	static const char *const names[] = {
 		[FUNCTIONFS_BIND] = "BIND",
 		[FUNCTIONFS_UNBIND] = "UNBIND",
 		[FUNCTIONFS_ENABLE] = "ENABLE",
 		[FUNCTIONFS_DISABLE] = "DISABLE",
 		[FUNCTIONFS_SETUP] = "SETUP",
 		[FUNCTIONFS_SUSPEND] = "SUSPEND",
 		[FUNCTIONFS_RESUME] = "RESUME",
 	};
 	switch (event->type) {
 	case FUNCTIONFS_BIND:
 	case FUNCTIONFS_UNBIND:
 	case FUNCTIONFS_ENABLE:
 	case FUNCTIONFS_DISABLE:
 	case FUNCTIONFS_SETUP:
 	case FUNCTIONFS_SUSPEND:
 	case FUNCTIONFS_RESUME:
 		printf("Event %s\n", names[event->type]);
 	}
 }

 static void handle_ep0(int ep0, bool *ready)
 {
 	struct usb_functionfs_event event;
 	int ret;

 	struct pollfd pfds[1];
 	pfds[0].fd = ep0;
 	pfds[0].events = POLLIN;

 	ret = poll(pfds, 1, 0);

 	if (ret && (pfds[0].revents & POLLIN)) {
 		ret = read(ep0, &event, sizeof(event));
 		if (!ret) {
 			perror("unable to read event from ep0");
 			return;
 		}
 		display_event(&event);
 		switch (event.type) {
 		case FUNCTIONFS_SETUP:
 			if (event.u.setup.bRequestType & USB_DIR_IN)
 				write(ep0, NULL, 0);
 			else
 				read(ep0, NULL, 0);
 			break;

 		case FUNCTIONFS_ENABLE:
 			*ready = true;
 			break;

 		case FUNCTIONFS_DISABLE:
 			*ready = false;
 			break;

 		default:
 			break;
 		}
 	}
 }

 int main(int argc, char *argv[])
 {
 	int i, ret;
 	char *ep_path;

 	int ep0;
 	int ep[2];

 	io_context_t ctx;

 	int evfd;
 	fd_set rfds;

 	char *buf_in, *buf_out;
 	struct iocb *iocb_in, *iocb_out;
 	int req_in = 0, req_out = 0;
 	bool ready;

 	if (argc != 2) {
 		printf("ffs directory not specified!\n");
 		return 1;
 	}

 	ep_path = malloc(strlen(argv[1]) + 4 /* "/ep#" */ + 1 /* '\0' */);
 	if (!ep_path) {
 		perror("malloc");
 		return 1;
 	}

 	/* open endpoint files */
 	sprintf(ep_path, "%s/ep0", argv[1]);
 	ep0 = open(ep_path, O_RDWR);
 	if (ep0 < 0) {
 		perror("unable to open ep0");
 		return 1;
 	}
 	if (write(ep0, &descriptors, sizeof(descriptors)) < 0) {
 		perror("unable do write descriptors");
 		return 1;
 	}
 	if (write(ep0, &strings, sizeof(strings)) < 0) {
 		perror("unable to write strings");
 		return 1;
 	}
 	for (i = 0; i < 2; ++i) {
 		sprintf(ep_path, "%s/ep%d", argv[1], i+1);
 		ep[i] = open(ep_path, O_RDWR);
 		if (ep[i] < 0) {
 			printf("unable to open ep%d: %s\n", i+1,
 			       strerror(errno));
 			return 1;
 		}
 	}

 	free(ep_path);

 	memset(&ctx, 0, sizeof(ctx));
 	/* setup aio context to handle up to 2 requests */
 	if (io_setup(2, &ctx) < 0) {
 		perror("unable to setup aio");
 		return 1;
 	}

 	evfd = eventfd(0, 0);
 	if (evfd < 0) {
 		perror("unable to open eventfd");
 		return 1;
 	}

 	/* alloc buffers and requests */
 	buf_in = malloc(BUF_LEN);
 	buf_out = malloc(BUF_LEN);
 	iocb_in = malloc(sizeof(*iocb_in));
 	iocb_out = malloc(sizeof(*iocb_out));

 	while (1) {
 		FD_ZERO(&rfds);
 		FD_SET(ep0, &rfds);
 		FD_SET(evfd, &rfds);

 		ret = select(((ep0 > evfd) ? ep0 : evfd)+1,
 			     &rfds, NULL, NULL, NULL);
 		if (ret < 0) {
 			if (errno == EINTR)
 				continue;
 			perror("select");
 			break;
 		}

 		if (FD_ISSET(ep0, &rfds))
 			handle_ep0(ep0, &ready);

 		/* we are waiting for function ENABLE */
 		if (!ready)
 			continue;

 		/* if something was submitted we wait for event */
 		if (FD_ISSET(evfd, &rfds)) {
 			uint64_t ev_cnt;
 			ret = read(evfd, &ev_cnt, sizeof(ev_cnt));
 			if (ret < 0) {
 				perror("unable to read eventfd");
 				break;
 			}

 			struct io_event e[2];
 			/* we wait for one event */
 			ret = io_getevents(ctx, 1, 2, e, NULL);
 			/* if we got event */
 			for (i = 0; i < ret; ++i) {
 				if (e[i].obj->aio_fildes == ep[0]) {
 					printf("ev=in; ret=%lu\n", e[i].res);
 					req_in = 0;
 				} else if (e[i].obj->aio_fildes == ep[1]) {
 					printf("ev=out; ret=%lu\n", e[i].res);
 					req_out = 0;
 				}
 			}
 		}

 		if (!req_in) { /* if IN transfer not requested*/
 			/* prepare write request */
 			io_prep_pwrite(iocb_in, ep[0], buf_in, BUF_LEN, 0);
 			/* enable eventfd notification */
 			iocb_in->u.c.flags |= IOCB_FLAG_RESFD;
 			iocb_in->u.c.resfd = evfd;
 			/* submit table of requests */
 			ret = io_submit(ctx, 1, &iocb_in);
 			if (ret >= 0) { /* if ret > 0 request is queued */
 				req_in = 1;
 				printf("submit: in\n");
 			} else
 				perror("unable to submit request");
 		}
 		if (!req_out) { /* if OUT transfer not requested */
 			/* prepare read request */
 			io_prep_pread(iocb_out, ep[1], buf_out, BUF_LEN, 0);
 			/* enable eventfs notification */
 			iocb_out->u.c.flags |= IOCB_FLAG_RESFD;
 			iocb_out->u.c.resfd = evfd;
 			/* submit table of requests */
 			ret = io_submit(ctx, 1, &iocb_out);
 			if (ret >= 0) { /* if ret > 0 request is queued */
 				req_out = 1;
 				printf("submit: out\n");
 			} else
 				perror("unable to submit request");
 		}
 	}

 	/* free resources */

 	io_destroy(ctx);

 	free(buf_in);
 	free(buf_out);
 	free(iocb_in);
 	free(iocb_out);

 	for (i = 0; i < 2; ++i)
 		close(ep[i]);
 	close(ep0);

 	return 0;
 }
	/*
	* This is free and unencumbered software released into the public domain.
	*
	* Anyone is free to copy, modify, publish, use, compile, sell, or
	* distribute this software, either in source code form or as a compiled
	* binary, for any purpose, commercial or non-commercial, and by any
	* means.
	*
	* In jurisdictions that recognize copyright laws, the author or authors
	* of this software dedicate any and all copyright interest in the
	* software to the public domain. We make this dedication for the benefit
	* of the public at large and to the detriment of our heirs and
	* successors. We intend this dedication to be an overt act of
	* relinquishment in perpetuity of all present and future rights to this
	* software under copyright law.
	*
	* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
	* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
	* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
	* IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR
	* OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
	* ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
	* OTHER DEALINGS IN THE SOFTWARE.
	*
	* For more information, please refer to <http://unlicense.org/>
	*/

	/* $(CROSS_COMPILE)cc -g -o aio_simple aio_simple.c -laio */

	#define _DEFAULT_SOURCE /* for endian.h */

	#include <endian.h>
	#include <errno.h>
	#include <fcntl.h>
	#include <stdarg.h>
	#include <stdio.h>
	#include <stdlib.h>
	#include <string.h>
	#include <sys/ioctl.h>
	#include <sys/stat.h>
	#include <sys/types.h>
	#include <sys/poll.h>
	#include <unistd.h>
	#include <stdbool.h>
	#include <sys/eventfd.h>

	#include "libaio.h"
	#define IOCB_FLAG_RESFD (1 << 0)

	#include <linux/usb/functionfs.h>

	#define BUF_LEN 8192

	/*
	* cpu_to_le16/32 are used when initializing structures, a context where a
	* function call is not allowed. To solve this, we code cpu_to_le16/32 in a way
	* that allows them to be used when initializing structures.
	*/

	#if BYTE_ORDER == __LITTLE_ENDIAN
	#define cpu_to_le16(x) (x)
	#define cpu_to_le32(x) (x)
	#else
	#define cpu_to_le16(x) ((((x) >> 8) & 0xffu) \| (((x) & 0xffu) << 8))
	#define cpu_to_le32(x) \
	((((x) & 0xff000000u) >> 24) \| (((x) & 0x00ff0000u) >> 8) \| \
	(((x) & 0x0000ff00u) << 8) \| (((x) & 0x000000ffu) << 24))
	#endif

	/****************** Descriptors and Strings *****************************/

	static const struct {
	struct usb_functionfs_descs_head_v2 header;
	__le32 fs_count;
	__le32 hs_count;
	struct {
	struct usb_interface_descriptor intf;
	struct usb_endpoint_descriptor_no_audio bulk_sink;
	struct usb_endpoint_descriptor_no_audio bulk_source;
	} __attribute__ ((__packed__)) fs_descs, hs_descs;
	} __attribute__ ((__packed__)) descriptors = {
	.header = {
	.magic = cpu_to_le32(FUNCTIONFS_DESCRIPTORS_MAGIC_V2),
	.flags = cpu_to_le32(FUNCTIONFS_HAS_FS_DESC \|
	FUNCTIONFS_HAS_HS_DESC),
	.length = cpu_to_le32(sizeof(descriptors)),
	},
	.fs_count = cpu_to_le32(3),
	.fs_descs = {
	.intf = {
	.bLength = sizeof(descriptors.fs_descs.intf),
	.bDescriptorType = USB_DT_INTERFACE,
	.bNumEndpoints = 2,
	.bInterfaceClass = USB_CLASS_VENDOR_SPEC,
	.iInterface = 1,
	},
	.bulk_sink = {
	.bLength = sizeof(descriptors.fs_descs.bulk_sink),
	.bDescriptorType = USB_DT_ENDPOINT,
	.bEndpointAddress = 1 \| USB_DIR_IN,
	.bmAttributes = USB_ENDPOINT_XFER_BULK,
	},
	.bulk_source = {
	.bLength = sizeof(descriptors.fs_descs.bulk_source),
	.bDescriptorType = USB_DT_ENDPOINT,
	.bEndpointAddress = 2 \| USB_DIR_OUT,
	.bmAttributes = USB_ENDPOINT_XFER_BULK,
	},
	},
	.hs_count = cpu_to_le32(3),
	.hs_descs = {
	.intf = {
	.bLength = sizeof(descriptors.hs_descs.intf),
	.bDescriptorType = USB_DT_INTERFACE,
	.bNumEndpoints = 2,
	.bInterfaceClass = USB_CLASS_VENDOR_SPEC,
	.iInterface = 1,
	},
	.bulk_sink = {
	.bLength = sizeof(descriptors.hs_descs.bulk_sink),
	.bDescriptorType = USB_DT_ENDPOINT,
	.bEndpointAddress = 1 \| USB_DIR_IN,
	.bmAttributes = USB_ENDPOINT_XFER_BULK,
	.wMaxPacketSize = cpu_to_le16(512),
	},
	.bulk_source = {
	.bLength = sizeof(descriptors.hs_descs.bulk_source),
	.bDescriptorType = USB_DT_ENDPOINT,
	.bEndpointAddress = 2 \| USB_DIR_OUT,
	.bmAttributes = USB_ENDPOINT_XFER_BULK,
	.wMaxPacketSize = cpu_to_le16(512),
	},
	},
	};

	#define STR_INTERFACE "AIO Test"

	static const struct {
	struct usb_functionfs_strings_head header;
	struct {
	__le16 code;
	const char str1[sizeof(STR_INTERFACE)];
	} __attribute__ ((__packed__)) lang0;
	} __attribute__ ((__packed__)) strings = {
	.header = {
	.magic = cpu_to_le32(FUNCTIONFS_STRINGS_MAGIC),
	.length = cpu_to_le32(sizeof(strings)),
	.str_count = cpu_to_le32(1),
	.lang_count = cpu_to_le32(1),
	},
	.lang0 = {
	cpu_to_le16(0x0409), /* en-us */
	STR_INTERFACE,
	},
	};

	/****************** Endpoints handling *****************************/

	static void display_event(struct usb_functionfs_event *event)
	{
	static const char *const names[] = {
	[FUNCTIONFS_BIND] = "BIND",
	[FUNCTIONFS_UNBIND] = "UNBIND",
	[FUNCTIONFS_ENABLE] = "ENABLE",
	[FUNCTIONFS_DISABLE] = "DISABLE",
	[FUNCTIONFS_SETUP] = "SETUP",
	[FUNCTIONFS_SUSPEND] = "SUSPEND",
	[FUNCTIONFS_RESUME] = "RESUME",
	};
	switch (event->type) {
	case FUNCTIONFS_BIND:
	case FUNCTIONFS_UNBIND:
	case FUNCTIONFS_ENABLE:
	case FUNCTIONFS_DISABLE:
	case FUNCTIONFS_SETUP:
	case FUNCTIONFS_SUSPEND:
	case FUNCTIONFS_RESUME:
	printf("Event %s\n", names[event->type]);
	}
	}

	static void handle_ep0(int ep0, bool *ready)
	{
	struct usb_functionfs_event event;
	int ret;

	struct pollfd pfds[1];
	pfds[0].fd = ep0;
	pfds[0].events = POLLIN;

	ret = poll(pfds, 1, 0);

	if (ret && (pfds[0].revents & POLLIN)) {
	ret = read(ep0, &event, sizeof(event));
	if (!ret) {
	perror("unable to read event from ep0");
	return;
	}
	display_event(&event);
	switch (event.type) {
	case FUNCTIONFS_SETUP:
	if (event.u.setup.bRequestType & USB_DIR_IN)
	write(ep0, NULL, 0);
	else
	read(ep0, NULL, 0);
	break;

	case FUNCTIONFS_ENABLE:
	*ready = true;
	break;

	case FUNCTIONFS_DISABLE:
	*ready = false;
	break;

	default:
	break;
	}
	}
	}

	int main(int argc, char *argv[])
	{
	int i, ret;
	char *ep_path;

	int ep0;
	int ep[2];

	io_context_t ctx;

	int evfd;
	fd_set rfds;

	char buf_in, buf_out;
	struct iocb iocb_in, iocb_out;
	int req_in = 0, req_out = 0;
	bool ready;

	if (argc != 2) {
	printf("ffs directory not specified!\n");
	return 1;
	}

	ep_path = malloc(strlen(argv[1]) + 4 /* "/ep#" / + 1 / '\0' */);
	if (!ep_path) {
	perror("malloc");
	return 1;
	}

	/* open endpoint files */
	sprintf(ep_path, "%s/ep0", argv[1]);
	ep0 = open(ep_path, O_RDWR);
	if (ep0 < 0) {
	perror("unable to open ep0");
	return 1;
	}
	if (write(ep0, &descriptors, sizeof(descriptors)) < 0) {
	perror("unable do write descriptors");
	return 1;
	}
	if (write(ep0, &strings, sizeof(strings)) < 0) {
	perror("unable to write strings");
	return 1;
	}
	for (i = 0; i < 2; ++i) {
	sprintf(ep_path, "%s/ep%d", argv[1], i+1);
	ep[i] = open(ep_path, O_RDWR);
	if (ep[i] < 0) {
	printf("unable to open ep%d: %s\n", i+1,
	strerror(errno));
	return 1;
	}
	}

	free(ep_path);

	memset(&ctx, 0, sizeof(ctx));
	/* setup aio context to handle up to 2 requests */
	if (io_setup(2, &ctx) < 0) {
	perror("unable to setup aio");
	return 1;
	}

	evfd = eventfd(0, 0);
	if (evfd < 0) {
	perror("unable to open eventfd");
	return 1;
	}

	/* alloc buffers and requests */
	buf_in = malloc(BUF_LEN);
	buf_out = malloc(BUF_LEN);
	iocb_in = malloc(sizeof(*iocb_in));
	iocb_out = malloc(sizeof(*iocb_out));

	while (1) {
	FD_ZERO(&rfds);
	FD_SET(ep0, &rfds);
	FD_SET(evfd, &rfds);

	ret = select(((ep0 > evfd) ? ep0 : evfd)+1,
	&rfds, NULL, NULL, NULL);
	if (ret < 0) {
	if (errno == EINTR)
	continue;
	perror("select");
	break;
	}

	if (FD_ISSET(ep0, &rfds))
	handle_ep0(ep0, &ready);

	/* we are waiting for function ENABLE */
	if (!ready)
	continue;

	/* if something was submitted we wait for event */
	if (FD_ISSET(evfd, &rfds)) {
	uint64_t ev_cnt;
	ret = read(evfd, &ev_cnt, sizeof(ev_cnt));
	if (ret < 0) {
	perror("unable to read eventfd");
	break;
	}

	struct io_event e[2];
	/* we wait for one event */
	ret = io_getevents(ctx, 1, 2, e, NULL);
	/* if we got event */
	for (i = 0; i < ret; ++i) {
	if (e[i].obj->aio_fildes == ep[0]) {
	printf("ev=in; ret=%lu\n", e[i].res);
	req_in = 0;
	} else if (e[i].obj->aio_fildes == ep[1]) {
	printf("ev=out; ret=%lu\n", e[i].res);
	req_out = 0;
	}
	}
	}

	if (!req_in) { /* if IN transfer not requested*/
	/* prepare write request */
	io_prep_pwrite(iocb_in, ep[0], buf_in, BUF_LEN, 0);
	/* enable eventfd notification */
	iocb_in->u.c.flags \|= IOCB_FLAG_RESFD;
	iocb_in->u.c.resfd = evfd;
	/* submit table of requests */
	ret = io_submit(ctx, 1, &iocb_in);
	if (ret >= 0) { /* if ret > 0 request is queued */
	req_in = 1;
	printf("submit: in\n");
	} else
	perror("unable to submit request");
	}
	if (!req_out) { /* if OUT transfer not requested */
	/* prepare read request */
	io_prep_pread(iocb_out, ep[1], buf_out, BUF_LEN, 0);
	/* enable eventfs notification */
	iocb_out->u.c.flags \|= IOCB_FLAG_RESFD;
	iocb_out->u.c.resfd = evfd;
	/* submit table of requests */
	ret = io_submit(ctx, 1, &iocb_out);
	if (ret >= 0) { /* if ret > 0 request is queued */
	req_out = 1;
	printf("submit: out\n");
	} else
	perror("unable to submit request");
	}
	}

	/* free resources */

	io_destroy(ctx);

	free(buf_in);
	free(buf_out);
	free(iocb_in);
	free(iocb_out);

	for (i = 0; i < 2; ++i)
	close(ep[i]);
	close(ep0);

	return 0;
	}