uinput: configurable device identity with fallback to built-in defaults

Add vmctl_uinput_id and an optional vmctl_config.uinput_id pointer. NULL keeps the built-in identity verbatim; a non-NULL config supplies all numeric fields literally, with the device name suffixed -A/-B for the dual-device mode.

include/vmctl.h

@@ -19,11 +19,20 @@ typedef enum {
 #define VMCTL_PTR_REL   2   /* uinput: relative mouse             */
 #define VMCTL_PTR_BOTH  3   /* uinput: two devices A=abs B=rel    */
 
+typedef struct {
+    unsigned    bustype;     /* HID bus type, e.g. 0x0003 (USB)    */
+    unsigned    vendor;      /* vendor id                          */
+    unsigned    product;     /* product id                         */
+    unsigned    version;     /* device version                     */
+    const char* name;        /* device name; library copies it     */
+} vmctl_uinput_id;
+
 typedef struct {
     vmctl_driver driver;
     const char*  qmp_path;   /* QMP unix socket; required for QMP, optional (passthrough) for UINPUT */
     const char*  input_bus;  /* virtio-input-host-pci bus "pci.0" for passthrough; "" = none         */
     int          ptr_mode;   /* UINPUT VMCTL_PTR_*; 0 for QMP                                         */
+    const vmctl_uinput_id* uinput_id;  /* UINPUT only; NULL = built-in defaults                       */
 } vmctl_config;
 
 vmctl_t* vmctl_open (const vmctl_config* cfg);   /* NULL on error    */

src/vmctl/linux/uinput_driver.c

@@ -50,7 +50,7 @@ static void emit(int fd, uint16_t type, uint16_t code, int32_t val) {
 
 static void syn(int fd) { emit(fd, EV_SYN, SYN_REPORT, 0); }
 
-static int uinput_create(int rel_motion, const char* name, char evdev[64]) {
+static int uinput_create(int rel_motion, const vmctl_uinput_id* id, const char* name, char evdev[64]) {
     int fd = open("/dev/uinput", O_RDWR | O_CLOEXEC);
     if (fd < 0) return -1;
 
@@ -89,10 +89,10 @@ static int uinput_create(int rel_motion, const char* name, char evdev[64]) {
 
     struct uinput_setup us;
     memset(&us, 0, sizeof us);
-    us.id.bustype = HWID_BUS;
+    us.id.bustype = (uint16_t)id->bustype;
-    us.id.vendor  = HWID_VENDOR;
+    us.id.vendor  = (uint16_t)id->vendor;
-    us.id.product = HWID_PRODUCT;
+    us.id.product = (uint16_t)id->product;
-    us.id.version = HWID_VERSION;
+    us.id.version = (uint16_t)id->version;
     strncpy(us.name, name, sizeof us.name - 1);
 
     if (ioctl(fd, UI_DEV_SETUP, &us) < 0 || ioctl(fd, UI_DEV_CREATE) < 0) {
@@ -201,13 +201,38 @@ vmctl_t* vmctl_open_uinput_driver(const vmctl_config* cfg) {
     v->ui_fd_a = -1;
     v->ui_fd_b = -1;
 
+    /* HID identity: NULL config selects the built-in defaults verbatim; a
+     * non-NULL config supplies all numeric fields literally (zeros included). */
+    const vmctl_uinput_id DEFAULT_ID = {
+        HWID_BUS, HWID_VENDOR, HWID_PRODUCT, HWID_VERSION, HWID_NAME_A
+    };
+    const vmctl_uinput_id* id = cfg->uinput_id ? cfg->uinput_id : &DEFAULT_ID;
+
+    /* Base name: caller's non-empty name, else NULL = use default A/B names. */
+    const char* base = (cfg->uinput_id && cfg->uinput_id->name && cfg->uinput_id->name[0])
+                       ? cfg->uinput_id->name : NULL;
+
+    /* A/B suffix is added by the library only when two devices are created
+     * (VMCTL_PTR_BOTH) and only over a caller-supplied base name. */
+    char name_a[UINPUT_MAX_NAME_SIZE];
+    char name_b[UINPUT_MAX_NAME_SIZE];
+    const char* dev_a = base ? base : HWID_NAME_A;
+    const char* dev_b = HWID_NAME_B;
+    if (cfg->ptr_mode == VMCTL_PTR_BOTH && base) {
+        int base_max = (int)(sizeof name_a - 1 /*NUL*/ - 2 /*"-A"*/);
+        snprintf(name_a, sizeof name_a, "%.*s-A", base_max, base);
+        snprintf(name_b, sizeof name_b, "%.*s-B", base_max, base);
+        dev_a = name_a;
+        dev_b = name_b;
+    }
+
     char evdev_a[64], evdev_b[64];
     int rel_a = (cfg->ptr_mode == VMCTL_PTR_REL);
-    v->ui_fd_a = uinput_create(rel_a, HWID_NAME_A, evdev_a);
+    v->ui_fd_a = uinput_create(rel_a, id, dev_a, evdev_a);
     if (v->ui_fd_a < 0) { free(v); return NULL; }
 
     if (cfg->ptr_mode == VMCTL_PTR_BOTH) {
-        v->ui_fd_b = uinput_create(1, HWID_NAME_B, evdev_b);
+        v->ui_fd_b = uinput_create(1, id, dev_b, evdev_b);
         if (v->ui_fd_b < 0) {
             ioctl(v->ui_fd_a, UI_DEV_DESTROY);
             close(v->ui_fd_a);