// SPDX-License-Identifier: GPL-2.0
#include <linux/slab.h> /* for kmalloc */
#include <linux/consolemap.h>
#include <linux/interrupt.h>
#include <linux/sched.h>
#include <linux/device.h> /* for dev_warn */
#include <linux/selection.h>
#include <linux/workqueue.h>
#include <linux/tty.h>
#include <linux/tty_flip.h>
#include <linux/atomic.h>
#include <linux/console.h>

#include "speakup.h"

unsigned short spk_xs, spk_ys, spk_xe, spk_ye; /* our region points */
struct vc_data *spk_sel_cons;

struct speakup_selection_work {
        struct work_struct work;
        struct tiocl_selection sel;
        struct tty_struct *tty;
};

static void __speakup_set_selection(struct work_struct *work)
{
        struct speakup_selection_work *ssw =
                container_of(work, struct speakup_selection_work, work);

        struct tty_struct *tty;
        struct tiocl_selection sel;

        sel = ssw->sel;

        /* this ensures we copy sel before releasing the lock below */
        rmb();

        /* release the lock by setting tty of the struct to NULL */
        tty = xchg(&ssw->tty, NULL);

        if (spk_sel_cons != vc_cons[fg_console].d) {
                spk_sel_cons = vc_cons[fg_console].d;
                pr_warn("Selection: mark console not the same as cut\n");
                goto unref;
        }

        console_lock();
        clear_selection();
        console_unlock();

        set_selection_kernel(&sel, tty);

unref:
        tty_kref_put(tty);
}

static struct speakup_selection_work speakup_sel_work = {
        .work = __WORK_INITIALIZER(speakup_sel_work.work,
                                   __speakup_set_selection)
};

int speakup_set_selection(struct tty_struct *tty)
{
        /* we get kref here first in order to avoid a subtle race when
         * cancelling selection work. getting kref first establishes the
         * invariant that if speakup_sel_work.tty is not NULL when
         * speakup_cancel_selection() is called, it must be the case that a put
         * kref is pending.
         */
        tty_kref_get(tty);
        if (cmpxchg(&speakup_sel_work.tty, NULL, tty)) {
                tty_kref_put(tty);
                return -EBUSY;
        }
        /* now we have the 'lock' by setting tty member of
         * speakup_selection_work. wmb() ensures that writes to
         * speakup_sel_work don't happen before cmpxchg() above.
         */
        wmb();

        speakup_sel_work.sel.xs = spk_xs + 1;
        speakup_sel_work.sel.ys = spk_ys + 1;
        speakup_sel_work.sel.xe = spk_xe + 1;
        speakup_sel_work.sel.ye = spk_ye + 1;
        speakup_sel_work.sel.sel_mode = TIOCL_SELCHAR;

        schedule_work_on(WORK_CPU_UNBOUND, &speakup_sel_work.work);

        return 0;
}

void speakup_cancel_selection(void)
{
        struct tty_struct *tty;

        cancel_work_sync(&speakup_sel_work.work);
        /* setting to null so that if work fails to run and we cancel it,
         * we can run it again without getting EBUSY forever from there on.
         * we need to use xchg here to avoid race with speakup_set_selection()
         */
        tty = xchg(&speakup_sel_work.tty, NULL);
        if (tty)
                tty_kref_put(tty);
}

static void __speakup_paste_selection(struct work_struct *work)
{
        struct speakup_selection_work *ssw =
                container_of(work, struct speakup_selection_work, work);
        struct tty_struct *tty = xchg(&ssw->tty, NULL);

        paste_selection(tty);
        tty_kref_put(tty);
}

static struct speakup_selection_work speakup_paste_work = {
        .work = __WORK_INITIALIZER(speakup_paste_work.work,
                                   __speakup_paste_selection)
};

int speakup_paste_selection(struct tty_struct *tty)
{
        tty_kref_get(tty);
        if (cmpxchg(&speakup_paste_work.tty, NULL, tty)) {
                tty_kref_put(tty);
                return -EBUSY;
        }

        schedule_work_on(WORK_CPU_UNBOUND, &speakup_paste_work.work);
        return 0;
}

void speakup_cancel_paste(void)
{
        struct tty_struct *tty;

        cancel_work_sync(&speakup_paste_work.work);
        tty = xchg(&speakup_paste_work.tty, NULL);
        if (tty)
                tty_kref_put(tty);
}