/* control.c — control-write SEAM ONLY (this never writes guest memory).
 *
 * The actual write is performed elsewhere, by a component that holds read-write
 * access to the region; this only builds the desired vgpu_control_t image from
 * the intent and computes the GVA + offset/length of the significant field range
 * for that atomic write under the ctrl_gen seqlock. There is no gva_write here
 * and there must not be — the source is a RO fd that would fault on a store anyway.
 *
 * The reported out_ctrl_gva is a GVA in the PRODUCER's user address space
 * (region base + VGPU_CONTROL_OFFSET, cached as r->ctrl_gva): the external write
 * MUST be performed under r->proc_cr3, NOT the System kcr3.
 */

#include "perception-internal.h"

int vgpup_build_control_write(vgpup_region* r, const vgpup_control_intent* in,
                              vgpu_control_t* out_frame, uint64_t* out_ctrl_gva,
                              uint32_t* out_off, uint32_t* out_len)
{
    if (!r || !in || !out_frame || !out_ctrl_gva || !out_off || !out_len) { return -1; }

    /* Fill the desired control image. ctrl_gen stays 0: the writer owns it under
     * the seqlock. consumer_tick/attached carry separate heartbeat/intent
     * semantics and are not part of this intent. */
    memset(out_frame, 0, sizeof *out_frame);
    out_frame->desired_state  = in->desired_state;
    out_frame->target_fps     = in->target_fps;
    out_frame->draw_cursor    = in->draw_cursor;
    out_frame->full_frame_req = in->full_frame_req;

    *out_ctrl_gva = r->ctrl_gva;   /* region base + VGPU_CONTROL_OFFSET (cached) */

    /* Significant range: desired_state .. full_frame_req (contiguous in the ABI),
     * i.e. offsetof(desired_state) through the end of full_frame_req. */
    *out_off = (uint32_t)offsetof(vgpu_control_t, desired_state);
    *out_len = (uint32_t)(offsetof(vgpu_control_t, full_frame_req) + sizeof(uint32_t)
                          - offsetof(vgpu_control_t, desired_state));
    return 0;
}