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authorLinus Torvalds <torvalds@linux-foundation.org>2026-08-23 13:28:57 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2026-08-23 13:28:57 -0700
commit4352b8aee98005853aa63f57d6377282de17a33f (patch)
tree27614d7a9ef05c32d089004e104364ce42324837 /samples/uhid
downloadlinux-stable-4352b8aee98005853aa63f57d6377282de17a33f.tar.gz
linux-stable-4352b8aee98005853aa63f57d6377282de17a33f.zip
Merge tag 'i3c/for-7.3' of git://git.kernel.org/pub/scm/linux/kernel/git/i3c/linuxgrafted
Pull I3C updates from Alexandre Belloni: "A new driver this cycle, for the AMD AXI I3C controller. There are also new features such as IBI wakeup support, SETAASA device discovery and ACPI support for the the DAA methods, meaning we can now communicate with the SPD devices on DDR5 modules. New driver: - AMD AXI I3C master controller Subsystem: - I3C Common Command Code (CCC) handling improvements, especially around GET CCCs - SETAASA device discovery support - ACPI support for all existing DAA methods like SETDASA, SETNEWDA as well as I2C devices on I3C bus - IBI-based wakeup support Drivers: - dw: SETAASA support - mipi-i3c-hci: advertise IBI wakeup capability, AMD_PT I3C controller support, PIO queue management support for HCI v1.2 - renesas: improve suspend to RAM support, add runtime PM support" * tag 'i3c/for-7.3' of git://git.kernel.org/pub/scm/linux/kernel/git/i3c/linux: (70 commits) i3c: dw: reduce do_daa time if there's no client i3c: mipi-i3c-hci: Add support for AMD_PT I3C controller i3c: mipi-i3c-hci: Add PIO queue management support for HCI v1.2 i3c: mipi-i3c-hci: Fix missing STAT_IBI_STATUS_THLD in PIO mode i3c: dw: rename "pclk" to "apb" to match dt-binding i3c: dw: make struct dw_i3c_cmd smaller i3c: dw: use COMMAND_PORT_TRANSFER_ARG instead of hardcoding i3c: renesas: Don't register devices when ENTDAA times out i3c: master: dw-i3c-master: fix OD timing for first broadcast i3c: mipi-i3c-hci: Advertise IBI wakeup capability i3c: mipi-i3c-hci: Factor out i3c_hci_sysdev() i3c: mipi-i3c-hci-pci: Propagate I3C wakeup requirements to PCI i3c: master: Reject IBI requests from non-IBI-capable devices i3c: master: Add helper to query bus wakeup requirements i3c: master: Report wakeup events for IBIs i3c: master: Support IBI-based wakeup capability i3c: master: Fix potential UAF in i3c_device_match() i3c: master: Fix potential UAF in i3c_device_uevent() i3c: Make dev->desc locking assumptions explicit i3c: master: Fix use-after-free of master->this ...
Diffstat (limited to 'samples/uhid')
-rw-r--r--samples/uhid/.gitignore2
-rw-r--r--samples/uhid/Makefile4
-rw-r--r--samples/uhid/uhid-example.c465
3 files changed, 471 insertions, 0 deletions
diff --git a/samples/uhid/.gitignore b/samples/uhid/.gitignore
new file mode 100644
index 000000000..0e0a5a929
--- /dev/null
+++ b/samples/uhid/.gitignore
@@ -0,0 +1,2 @@
+# SPDX-License-Identifier: GPL-2.0-only
+/uhid-example
diff --git a/samples/uhid/Makefile b/samples/uhid/Makefile
new file mode 100644
index 000000000..0aa424ec4
--- /dev/null
+++ b/samples/uhid/Makefile
@@ -0,0 +1,4 @@
+# SPDX-License-Identifier: GPL-2.0-only
+userprogs-always-y += uhid-example
+
+userccflags += -I usr/include
diff --git a/samples/uhid/uhid-example.c b/samples/uhid/uhid-example.c
new file mode 100644
index 000000000..015cb06a2
--- /dev/null
+++ b/samples/uhid/uhid-example.c
@@ -0,0 +1,465 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * UHID Example
+ *
+ * Copyright (c) 2012-2013 David Herrmann <dh.herrmann@gmail.com>
+ *
+ * The code may be used by anyone for any purpose,
+ * and can serve as a starting point for developing
+ * applications using uhid.
+ */
+
+/*
+ * UHID Example
+ * This example emulates a basic 3 buttons mouse with wheel over UHID. Run this
+ * program as root and then use the following keys to control the mouse:
+ * q: Quit the application
+ * 1: Toggle left button (down, up, ...)
+ * 2: Toggle right button
+ * 3: Toggle middle button
+ * a: Move mouse left
+ * d: Move mouse right
+ * w: Move mouse up
+ * s: Move mouse down
+ * r: Move wheel up
+ * f: Move wheel down
+ *
+ * Additionally to 3 button mouse, 3 keyboard LEDs are also supported (LED_NUML,
+ * LED_CAPSL and LED_SCROLLL). The device doesn't generate any related keyboard
+ * events, though. You need to manually write the EV_LED/LED_XY/1 activation
+ * input event to the evdev device to see it being sent to this device.
+ *
+ * If uhid is not available as /dev/uhid, then you can pass a different path as
+ * first argument.
+ * If <linux/uhid.h> is not installed in /usr, then compile this with:
+ * gcc -o ./uhid_test -Wall -I./include ./samples/uhid/uhid-example.c
+ * And ignore the warning about kernel headers. However, it is recommended to
+ * use the installed uhid.h if available.
+ */
+
+#include <errno.h>
+#include <fcntl.h>
+#include <poll.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <termios.h>
+#include <unistd.h>
+#include <linux/uhid.h>
+
+/*
+ * HID Report Desciptor
+ * We emulate a basic 3 button mouse with wheel and 3 keyboard LEDs. This is
+ * the report-descriptor as the kernel will parse it:
+ *
+ * INPUT(1)[INPUT]
+ * Field(0)
+ * Physical(GenericDesktop.Pointer)
+ * Application(GenericDesktop.Mouse)
+ * Usage(3)
+ * Button.0001
+ * Button.0002
+ * Button.0003
+ * Logical Minimum(0)
+ * Logical Maximum(1)
+ * Report Size(1)
+ * Report Count(3)
+ * Report Offset(0)
+ * Flags( Variable Absolute )
+ * Field(1)
+ * Physical(GenericDesktop.Pointer)
+ * Application(GenericDesktop.Mouse)
+ * Usage(3)
+ * GenericDesktop.X
+ * GenericDesktop.Y
+ * GenericDesktop.Wheel
+ * Logical Minimum(-128)
+ * Logical Maximum(127)
+ * Report Size(8)
+ * Report Count(3)
+ * Report Offset(8)
+ * Flags( Variable Relative )
+ * OUTPUT(2)[OUTPUT]
+ * Field(0)
+ * Application(GenericDesktop.Keyboard)
+ * Usage(3)
+ * LED.NumLock
+ * LED.CapsLock
+ * LED.ScrollLock
+ * Logical Minimum(0)
+ * Logical Maximum(1)
+ * Report Size(1)
+ * Report Count(3)
+ * Report Offset(0)
+ * Flags( Variable Absolute )
+ *
+ * This is the mapping that we expect:
+ * Button.0001 ---> Key.LeftBtn
+ * Button.0002 ---> Key.RightBtn
+ * Button.0003 ---> Key.MiddleBtn
+ * GenericDesktop.X ---> Relative.X
+ * GenericDesktop.Y ---> Relative.Y
+ * GenericDesktop.Wheel ---> Relative.Wheel
+ * LED.NumLock ---> LED.NumLock
+ * LED.CapsLock ---> LED.CapsLock
+ * LED.ScrollLock ---> LED.ScrollLock
+ *
+ * This information can be verified by reading /sys/kernel/debug/hid/<dev>/rdesc
+ * This file should print the same information as showed above.
+ */
+
+static unsigned char rdesc[] = {
+ 0x05, 0x01, /* USAGE_PAGE (Generic Desktop) */
+ 0x09, 0x02, /* USAGE (Mouse) */
+ 0xa1, 0x01, /* COLLECTION (Application) */
+ 0x09, 0x01, /* USAGE (Pointer) */
+ 0xa1, 0x00, /* COLLECTION (Physical) */
+ 0x85, 0x01, /* REPORT_ID (1) */
+ 0x05, 0x09, /* USAGE_PAGE (Button) */
+ 0x19, 0x01, /* USAGE_MINIMUM (Button 1) */
+ 0x29, 0x03, /* USAGE_MAXIMUM (Button 3) */
+ 0x15, 0x00, /* LOGICAL_MINIMUM (0) */
+ 0x25, 0x01, /* LOGICAL_MAXIMUM (1) */
+ 0x95, 0x03, /* REPORT_COUNT (3) */
+ 0x75, 0x01, /* REPORT_SIZE (1) */
+ 0x81, 0x02, /* INPUT (Data,Var,Abs) */
+ 0x95, 0x01, /* REPORT_COUNT (1) */
+ 0x75, 0x05, /* REPORT_SIZE (5) */
+ 0x81, 0x01, /* INPUT (Cnst,Var,Abs) */
+ 0x05, 0x01, /* USAGE_PAGE (Generic Desktop) */
+ 0x09, 0x30, /* USAGE (X) */
+ 0x09, 0x31, /* USAGE (Y) */
+ 0x09, 0x38, /* USAGE (WHEEL) */
+ 0x15, 0x81, /* LOGICAL_MINIMUM (-127) */
+ 0x25, 0x7f, /* LOGICAL_MAXIMUM (127) */
+ 0x75, 0x08, /* REPORT_SIZE (8) */
+ 0x95, 0x03, /* REPORT_COUNT (3) */
+ 0x81, 0x06, /* INPUT (Data,Var,Rel) */
+ 0xc0, /* END_COLLECTION */
+ 0xc0, /* END_COLLECTION */
+ 0x05, 0x01, /* USAGE_PAGE (Generic Desktop) */
+ 0x09, 0x06, /* USAGE (Keyboard) */
+ 0xa1, 0x01, /* COLLECTION (Application) */
+ 0x85, 0x02, /* REPORT_ID (2) */
+ 0x05, 0x08, /* USAGE_PAGE (Led) */
+ 0x19, 0x01, /* USAGE_MINIMUM (1) */
+ 0x29, 0x03, /* USAGE_MAXIMUM (3) */
+ 0x15, 0x00, /* LOGICAL_MINIMUM (0) */
+ 0x25, 0x01, /* LOGICAL_MAXIMUM (1) */
+ 0x95, 0x03, /* REPORT_COUNT (3) */
+ 0x75, 0x01, /* REPORT_SIZE (1) */
+ 0x91, 0x02, /* Output (Data,Var,Abs) */
+ 0x95, 0x01, /* REPORT_COUNT (1) */
+ 0x75, 0x05, /* REPORT_SIZE (5) */
+ 0x91, 0x01, /* Output (Cnst,Var,Abs) */
+ 0xc0, /* END_COLLECTION */
+};
+
+static int uhid_write(int fd, const struct uhid_event *ev)
+{
+ ssize_t ret;
+
+ ret = write(fd, ev, sizeof(*ev));
+ if (ret < 0) {
+ fprintf(stderr, "Cannot write to uhid: %m\n");
+ return -errno;
+ } else if (ret != sizeof(*ev)) {
+ fprintf(stderr, "Wrong size written to uhid: %zd != %zu\n",
+ ret, sizeof(ev));
+ return -EFAULT;
+ } else {
+ return 0;
+ }
+}
+
+static int create(int fd)
+{
+ struct uhid_event ev;
+
+ memset(&ev, 0, sizeof(ev));
+ ev.type = UHID_CREATE;
+ strcpy((char*)ev.u.create.name, "test-uhid-device");
+ ev.u.create.rd_data = rdesc;
+ ev.u.create.rd_size = sizeof(rdesc);
+ ev.u.create.bus = BUS_USB;
+ ev.u.create.vendor = 0x15d9;
+ ev.u.create.product = 0x0a37;
+ ev.u.create.version = 0;
+ ev.u.create.country = 0;
+
+ return uhid_write(fd, &ev);
+}
+
+static void destroy(int fd)
+{
+ struct uhid_event ev;
+
+ memset(&ev, 0, sizeof(ev));
+ ev.type = UHID_DESTROY;
+
+ uhid_write(fd, &ev);
+}
+
+/* This parses raw output reports sent by the kernel to the device. A normal
+ * uhid program shouldn't do this but instead just forward the raw report.
+ * However, for ducomentational purposes, we try to detect LED events here and
+ * print debug messages for it. */
+static void handle_output(struct uhid_event *ev)
+{
+ /* LED messages are adverised via OUTPUT reports; ignore the rest */
+ if (ev->u.output.rtype != UHID_OUTPUT_REPORT)
+ return;
+ /* LED reports have length 2 bytes */
+ if (ev->u.output.size != 2)
+ return;
+ /* first byte is report-id which is 0x02 for LEDs in our rdesc */
+ if (ev->u.output.data[0] != 0x2)
+ return;
+
+ /* print flags payload */
+ fprintf(stderr, "LED output report received with flags %x\n",
+ ev->u.output.data[1]);
+}
+
+static int event(int fd)
+{
+ struct uhid_event ev;
+ ssize_t ret;
+
+ memset(&ev, 0, sizeof(ev));
+ ret = read(fd, &ev, sizeof(ev));
+ if (ret == 0) {
+ fprintf(stderr, "Read HUP on uhid-cdev\n");
+ return -EFAULT;
+ } else if (ret < 0) {
+ fprintf(stderr, "Cannot read uhid-cdev: %m\n");
+ return -errno;
+ } else if (ret != sizeof(ev)) {
+ fprintf(stderr, "Invalid size read from uhid-dev: %zd != %zu\n",
+ ret, sizeof(ev));
+ return -EFAULT;
+ }
+
+ switch (ev.type) {
+ case UHID_START:
+ fprintf(stderr, "UHID_START from uhid-dev\n");
+ break;
+ case UHID_STOP:
+ fprintf(stderr, "UHID_STOP from uhid-dev\n");
+ break;
+ case UHID_OPEN:
+ fprintf(stderr, "UHID_OPEN from uhid-dev\n");
+ break;
+ case UHID_CLOSE:
+ fprintf(stderr, "UHID_CLOSE from uhid-dev\n");
+ break;
+ case UHID_OUTPUT:
+ fprintf(stderr, "UHID_OUTPUT from uhid-dev\n");
+ handle_output(&ev);
+ break;
+ case UHID_OUTPUT_EV:
+ fprintf(stderr, "UHID_OUTPUT_EV from uhid-dev\n");
+ break;
+ default:
+ fprintf(stderr, "Invalid event from uhid-dev: %u\n", ev.type);
+ }
+
+ return 0;
+}
+
+static bool btn1_down;
+static bool btn2_down;
+static bool btn3_down;
+static signed char abs_hor;
+static signed char abs_ver;
+static signed char wheel;
+
+static int send_event(int fd)
+{
+ struct uhid_event ev;
+
+ memset(&ev, 0, sizeof(ev));
+ ev.type = UHID_INPUT;
+ ev.u.input.size = 5;
+
+ ev.u.input.data[0] = 0x1;
+ if (btn1_down)
+ ev.u.input.data[1] |= 0x1;
+ if (btn2_down)
+ ev.u.input.data[1] |= 0x2;
+ if (btn3_down)
+ ev.u.input.data[1] |= 0x4;
+
+ ev.u.input.data[2] = abs_hor;
+ ev.u.input.data[3] = abs_ver;
+ ev.u.input.data[4] = wheel;
+
+ return uhid_write(fd, &ev);
+}
+
+static int keyboard(int fd)
+{
+ char buf[128];
+ ssize_t ret, i;
+
+ ret = read(STDIN_FILENO, buf, sizeof(buf));
+ if (ret == 0) {
+ fprintf(stderr, "Read HUP on stdin\n");
+ return -EFAULT;
+ } else if (ret < 0) {
+ fprintf(stderr, "Cannot read stdin: %m\n");
+ return -errno;
+ }
+
+ for (i = 0; i < ret; ++i) {
+ switch (buf[i]) {
+ case '1':
+ btn1_down = !btn1_down;
+ ret = send_event(fd);
+ if (ret)
+ return ret;
+ break;
+ case '2':
+ btn2_down = !btn2_down;
+ ret = send_event(fd);
+ if (ret)
+ return ret;
+ break;
+ case '3':
+ btn3_down = !btn3_down;
+ ret = send_event(fd);
+ if (ret)
+ return ret;
+ break;
+ case 'a':
+ abs_hor = -20;
+ ret = send_event(fd);
+ abs_hor = 0;
+ if (ret)
+ return ret;
+ break;
+ case 'd':
+ abs_hor = 20;
+ ret = send_event(fd);
+ abs_hor = 0;
+ if (ret)
+ return ret;
+ break;
+ case 'w':
+ abs_ver = -20;
+ ret = send_event(fd);
+ abs_ver = 0;
+ if (ret)
+ return ret;
+ break;
+ case 's':
+ abs_ver = 20;
+ ret = send_event(fd);
+ abs_ver = 0;
+ if (ret)
+ return ret;
+ break;
+ case 'r':
+ wheel = 1;
+ ret = send_event(fd);
+ wheel = 0;
+ if (ret)
+ return ret;
+ break;
+ case 'f':
+ wheel = -1;
+ ret = send_event(fd);
+ wheel = 0;
+ if (ret)
+ return ret;
+ break;
+ case 'q':
+ return -ECANCELED;
+ default:
+ fprintf(stderr, "Invalid input: %c\n", buf[i]);
+ }
+ }
+
+ return 0;
+}
+
+int main(int argc, char **argv)
+{
+ int fd;
+ const char *path = "/dev/uhid";
+ struct pollfd pfds[2];
+ int ret;
+ struct termios state;
+
+ ret = tcgetattr(STDIN_FILENO, &state);
+ if (ret) {
+ fprintf(stderr, "Cannot get tty state\n");
+ } else {
+ state.c_lflag &= ~ICANON;
+ state.c_cc[VMIN] = 1;
+ ret = tcsetattr(STDIN_FILENO, TCSANOW, &state);
+ if (ret)
+ fprintf(stderr, "Cannot set tty state\n");
+ }
+
+ if (argc >= 2) {
+ if (!strcmp(argv[1], "-h") || !strcmp(argv[1], "--help")) {
+ fprintf(stderr, "Usage: %s [%s]\n", argv[0], path);
+ return EXIT_SUCCESS;
+ } else {
+ path = argv[1];
+ }
+ }
+
+ fprintf(stderr, "Open uhid-cdev %s\n", path);
+ fd = open(path, O_RDWR | O_CLOEXEC);
+ if (fd < 0) {
+ fprintf(stderr, "Cannot open uhid-cdev %s: %m\n", path);
+ return EXIT_FAILURE;
+ }
+
+ fprintf(stderr, "Create uhid device\n");
+ ret = create(fd);
+ if (ret) {
+ close(fd);
+ return EXIT_FAILURE;
+ }
+
+ pfds[0].fd = STDIN_FILENO;
+ pfds[0].events = POLLIN;
+ pfds[1].fd = fd;
+ pfds[1].events = POLLIN;
+
+ fprintf(stderr, "Press 'q' to quit...\n");
+ while (1) {
+ ret = poll(pfds, 2, -1);
+ if (ret < 0) {
+ fprintf(stderr, "Cannot poll for fds: %m\n");
+ break;
+ }
+ if (pfds[0].revents & POLLHUP) {
+ fprintf(stderr, "Received HUP on stdin\n");
+ break;
+ }
+ if (pfds[1].revents & POLLHUP) {
+ fprintf(stderr, "Received HUP on uhid-cdev\n");
+ break;
+ }
+
+ if (pfds[0].revents & POLLIN) {
+ ret = keyboard(fd);
+ if (ret)
+ break;
+ }
+ if (pfds[1].revents & POLLIN) {
+ ret = event(fd);
+ if (ret)
+ break;
+ }
+ }
+
+ fprintf(stderr, "Destroy uhid device\n");
+ destroy(fd);
+ return EXIT_SUCCESS;
+}