scrcpy/app/src/hid/hid_keyboard.c
Romain Vimont ccb5dd1c0e Extract keyboard HID handling
Split the keyboard implementation using AOA and the code handling HID
events, so that HID events can be reused for another protocol (UHID).
2024-02-25 18:33:02 +01:00

333 lines
9.9 KiB
C

#include "hid_keyboard.h"
#include <string.h>
#include "util/log.h"
#define SC_HID_MOD_NONE 0x00
#define SC_HID_MOD_LEFT_CONTROL (1 << 0)
#define SC_HID_MOD_LEFT_SHIFT (1 << 1)
#define SC_HID_MOD_LEFT_ALT (1 << 2)
#define SC_HID_MOD_LEFT_GUI (1 << 3)
#define SC_HID_MOD_RIGHT_CONTROL (1 << 4)
#define SC_HID_MOD_RIGHT_SHIFT (1 << 5)
#define SC_HID_MOD_RIGHT_ALT (1 << 6)
#define SC_HID_MOD_RIGHT_GUI (1 << 7)
#define SC_HID_KEYBOARD_INDEX_MODS 0
#define SC_HID_KEYBOARD_INDEX_KEYS 2
// USB HID protocol says 6 keys in an event is the requirement for BIOS
// keyboard support, though OS could support more keys via modifying the report
// desc. 6 should be enough for scrcpy.
#define SC_HID_KEYBOARD_MAX_KEYS 6
#define SC_HID_KEYBOARD_EVENT_SIZE \
(SC_HID_KEYBOARD_INDEX_KEYS + SC_HID_KEYBOARD_MAX_KEYS)
#define SC_HID_RESERVED 0x00
#define SC_HID_ERROR_ROLL_OVER 0x01
/**
* For HID, only report descriptor is needed.
*
* The specification is available here:
* <https://www.usb.org/sites/default/files/hid1_11.pdf>
*
* In particular, read:
* - 6.2.2 Report Descriptor
* - Appendix B.1 Protocol 1 (Keyboard)
* - Appendix C: Keyboard Implementation
*
* Normally a basic HID keyboard uses 8 bytes:
* Modifier Reserved Key Key Key Key Key Key
*
* You can dump your device's report descriptor with:
*
* sudo usbhid-dump -m vid:pid -e descriptor
*
* (change vid:pid' to your device's vendor ID and product ID).
*/
const uint8_t SC_HID_KEYBOARD_REPORT_DESC[] = {
// Usage Page (Generic Desktop)
0x05, 0x01,
// Usage (Keyboard)
0x09, 0x06,
// Collection (Application)
0xA1, 0x01,
// Usage Page (Key Codes)
0x05, 0x07,
// Usage Minimum (224)
0x19, 0xE0,
// Usage Maximum (231)
0x29, 0xE7,
// Logical Minimum (0)
0x15, 0x00,
// Logical Maximum (1)
0x25, 0x01,
// Report Size (1)
0x75, 0x01,
// Report Count (8)
0x95, 0x08,
// Input (Data, Variable, Absolute): Modifier byte
0x81, 0x02,
// Report Size (8)
0x75, 0x08,
// Report Count (1)
0x95, 0x01,
// Input (Constant): Reserved byte
0x81, 0x01,
// Usage Page (LEDs)
0x05, 0x08,
// Usage Minimum (1)
0x19, 0x01,
// Usage Maximum (5)
0x29, 0x05,
// Report Size (1)
0x75, 0x01,
// Report Count (5)
0x95, 0x05,
// Output (Data, Variable, Absolute): LED report
0x91, 0x02,
// Report Size (3)
0x75, 0x03,
// Report Count (1)
0x95, 0x01,
// Output (Constant): LED report padding
0x91, 0x01,
// Usage Page (Key Codes)
0x05, 0x07,
// Usage Minimum (0)
0x19, 0x00,
// Usage Maximum (101)
0x29, SC_HID_KEYBOARD_KEYS - 1,
// Logical Minimum (0)
0x15, 0x00,
// Logical Maximum(101)
0x25, SC_HID_KEYBOARD_KEYS - 1,
// Report Size (8)
0x75, 0x08,
// Report Count (6)
0x95, SC_HID_KEYBOARD_MAX_KEYS,
// Input (Data, Array): Keys
0x81, 0x00,
// End Collection
0xC0
};
const size_t SC_HID_KEYBOARD_REPORT_DESC_LEN =
sizeof(SC_HID_KEYBOARD_REPORT_DESC);
/**
* A keyboard HID event is 8 bytes long:
*
* - byte 0: modifiers (1 flag per modifier key, 8 possible modifier keys)
* - byte 1: reserved (always 0)
* - bytes 2 to 7: pressed keys (6 at most)
*
* 7 6 5 4 3 2 1 0
* +---------------+
* byte 0: |. . . . . . . .| modifiers
* +---------------+
* ^ ^ ^ ^ ^ ^ ^ ^
* | | | | | | | `- left Ctrl
* | | | | | | `--- left Shift
* | | | | | `----- left Alt
* | | | | `------- left Gui
* | | | `--------- right Ctrl
* | | `----------- right Shift
* | `------------- right Alt
* `--------------- right Gui
*
* +---------------+
* byte 1: |0 0 0 0 0 0 0 0| reserved
* +---------------+
*
* +---------------+
* bytes 2 to 7: |. . . . . . . .| scancode of 1st key pressed
* +---------------+
* |. . . . . . . .| scancode of 2nd key pressed
* +---------------+
* |. . . . . . . .| scancode of 3rd key pressed
* +---------------+
* |. . . . . . . .| scancode of 4th key pressed
* +---------------+
* |. . . . . . . .| scancode of 5th key pressed
* +---------------+
* |. . . . . . . .| scancode of 6th key pressed
* +---------------+
*
* If there are less than 6 keys pressed, the last items are set to 0.
* For example, if A and W are pressed:
*
* +---------------+
* bytes 2 to 7: |0 0 0 0 0 1 0 0| A is pressed (scancode = 4)
* +---------------+
* |0 0 0 1 1 0 1 0| W is pressed (scancode = 26)
* +---------------+
* |0 0 0 0 0 0 0 0| ^
* +---------------+ | only 2 keys are pressed, the
* |0 0 0 0 0 0 0 0| | remaining items are set to 0
* +---------------+ |
* |0 0 0 0 0 0 0 0| |
* +---------------+ |
* |0 0 0 0 0 0 0 0| v
* +---------------+
*
* Pressing more than 6 keys is not supported. If this happens (typically,
* never in practice), report a "phantom state":
*
* +---------------+
* bytes 2 to 7: |0 0 0 0 0 0 0 1| ^
* +---------------+ |
* |0 0 0 0 0 0 0 1| | more than 6 keys pressed:
* +---------------+ | the list is filled with a special
* |0 0 0 0 0 0 0 1| | rollover error code (0x01)
* +---------------+ |
* |0 0 0 0 0 0 0 1| |
* +---------------+ |
* |0 0 0 0 0 0 0 1| |
* +---------------+ |
* |0 0 0 0 0 0 0 1| v
* +---------------+
*/
static void
sc_hid_keyboard_event_init(struct sc_hid_event *hid_event) {
hid_event->size = SC_HID_KEYBOARD_EVENT_SIZE;
uint8_t *data = hid_event->data;
data[SC_HID_KEYBOARD_INDEX_MODS] = SC_HID_MOD_NONE;
data[1] = SC_HID_RESERVED;
memset(&data[SC_HID_KEYBOARD_INDEX_KEYS], 0, SC_HID_KEYBOARD_MAX_KEYS);
}
static uint16_t
sc_hid_mod_from_sdl_keymod(uint16_t mod) {
uint16_t mods = SC_HID_MOD_NONE;
if (mod & SC_MOD_LCTRL) {
mods |= SC_HID_MOD_LEFT_CONTROL;
}
if (mod & SC_MOD_LSHIFT) {
mods |= SC_HID_MOD_LEFT_SHIFT;
}
if (mod & SC_MOD_LALT) {
mods |= SC_HID_MOD_LEFT_ALT;
}
if (mod & SC_MOD_LGUI) {
mods |= SC_HID_MOD_LEFT_GUI;
}
if (mod & SC_MOD_RCTRL) {
mods |= SC_HID_MOD_RIGHT_CONTROL;
}
if (mod & SC_MOD_RSHIFT) {
mods |= SC_HID_MOD_RIGHT_SHIFT;
}
if (mod & SC_MOD_RALT) {
mods |= SC_HID_MOD_RIGHT_ALT;
}
if (mod & SC_MOD_RGUI) {
mods |= SC_HID_MOD_RIGHT_GUI;
}
return mods;
}
void
sc_hid_keyboard_init(struct sc_hid_keyboard *hid) {
memset(hid->keys, false, SC_HID_KEYBOARD_KEYS);
}
static inline bool
scancode_is_modifier(enum sc_scancode scancode) {
return scancode >= SC_SCANCODE_LCTRL && scancode <= SC_SCANCODE_RGUI;
}
bool
sc_hid_keyboard_event_from_key(struct sc_hid_keyboard *hid,
struct sc_hid_event *hid_event,
const struct sc_key_event *event) {
enum sc_scancode scancode = event->scancode;
assert(scancode >= 0);
// SDL also generates events when only modifiers are pressed, we cannot
// ignore them totally, for example press 'a' first then press 'Control',
// if we ignore 'Control' event, only 'a' is sent.
if (scancode >= SC_HID_KEYBOARD_KEYS && !scancode_is_modifier(scancode)) {
// Scancode to ignore
return false;
}
sc_hid_keyboard_event_init(hid_event);
uint16_t mods = sc_hid_mod_from_sdl_keymod(event->mods_state);
if (scancode < SC_HID_KEYBOARD_KEYS) {
// Pressed is true and released is false
hid->keys[scancode] = (event->action == SC_ACTION_DOWN);
LOGV("keys[%02x] = %s", scancode,
hid->keys[scancode] ? "true" : "false");
}
hid_event->data[SC_HID_KEYBOARD_INDEX_MODS] = mods;
uint8_t *keys_data = &hid_event->data[SC_HID_KEYBOARD_INDEX_KEYS];
// Re-calculate pressed keys every time
int keys_pressed_count = 0;
for (int i = 0; i < SC_HID_KEYBOARD_KEYS; ++i) {
if (hid->keys[i]) {
// USB HID protocol says that if keys exceeds report count, a
// phantom state should be reported
if (keys_pressed_count >= SC_HID_KEYBOARD_MAX_KEYS) {
// Phantom state:
// - Modifiers
// - Reserved
// - ErrorRollOver * HID_MAX_KEYS
memset(keys_data, SC_HID_ERROR_ROLL_OVER,
SC_HID_KEYBOARD_MAX_KEYS);
goto end;
}
keys_data[keys_pressed_count] = i;
++keys_pressed_count;
}
}
end:
LOGV("hid keyboard: key %-4s scancode=%02x (%u) mod=%02x",
event->action == SC_ACTION_DOWN ? "down" : "up", event->scancode,
event->scancode, mods);
return true;
}
bool
sc_hid_keyboard_event_from_mods(struct sc_hid_event *event,
uint16_t mods_state) {
bool capslock = mods_state & SC_MOD_CAPS;
bool numlock = mods_state & SC_MOD_NUM;
if (!capslock && !numlock) {
// Nothing to do
return false;
}
sc_hid_keyboard_event_init(event);
unsigned i = 0;
if (capslock) {
event->data[SC_HID_KEYBOARD_INDEX_KEYS + i] = SC_SCANCODE_CAPSLOCK;
++i;
}
if (numlock) {
event->data[SC_HID_KEYBOARD_INDEX_KEYS + i] = SC_SCANCODE_NUMLOCK;
++i;
}
return true;
}