Initial commit

COPYING

+Copyright 2005-2006 Luc Verhaegen.
+
+Permission is hereby granted, free of charge, to any person obtaining a
+copy of this software and associated documentation files (the "Software"),
+to deal in the Software without restriction, including without limitation
+the rights to use, copy, modify, merge, publish, distribute, sublicense,
+and/or sell copies of the Software, and to permit persons to whom the
+Software is furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR
+OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
+ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
+OTHER DEALINGS IN THE SOFTWARE.
+
+
+
+Copyright 2005-2006 Luc Verhaegen.
+Copyright © 2021 Red Hat, Inc.
+
+Permission is hereby granted, free of charge, to any person obtaining a
+copy of this software and associated documentation files (the "Software"),
+to deal in the Software without restriction, including without limitation
+the rights to use, copy, modify, merge, publish, distribute, sublicense,
+and/or sell copies of the Software, and to permit persons to whom the
+Software is furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR
+OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
+ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
+OTHER DEALINGS IN THE SOFTWARE.
+
+
+
+Copyright © 2000 Compaq Computer Corporation
+Copyright © 2002 Hewlett Packard Company
+Copyright © 2006 Intel Corporation
+Copyright © 2008, 2021 Red Hat, Inc.
+
+Permission to use, copy, modify, distribute, and sell this software and its
+documentation for any purpose is hereby granted without fee, provided that
+the above copyright notice appear in all copies and that both that copyright
+notice and this permission notice appear in supporting documentation, and
+that the name of the copyright holders not be used in advertising or
+publicity pertaining to distribution of the software without specific,
+written prior permission.  The copyright holders make no representations
+about the suitability of this software for any purpose.  It is provided "as
+is" without express or implied warranty.
+
+THE COPYRIGHT HOLDERS DISCLAIM ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
+INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO
+EVENT SHALL THE COPYRIGHT HOLDERS BE LIABLE FOR ANY SPECIAL, INDIRECT OR
+CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE,
+DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
+TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
+OF THIS SOFTWARE.

README.md

+libxcvt
+=======
+
+`libxcvt` is a library providing a standalone version of the X server
+implementation of the VESA CVT standard timing modelines generator.
+
+`libxcvt` also provides a standalone version of the command line tool
+`cvt` copied from the Xorg implementation and is meant to be a direct
+replacement to the version provided by the `Xorg` server.
+
+An example output is:
+
+```
+$ $ cvt --verbose 1920 1200 75
+# 1920x1200 74.93 Hz (CVT 2.30MA) hsync: 94.04 kHz; pclk: 245.25 MHz
+Modeline "1920x1200_75.00"  245.25  1920 2064 2264 2608  1200 1203 1209 1255 -hsync +vsync
+```
+
+Building
+========
+
+`libxcvt` is built using [Meson](https://mesonbuild.com/)
+
+	$ git clone https://gitlab.freedesktop.org/ofourdan/libxcvt.git
+	$ cd libxcvt
+	$ meson build/ --prefix=...
+	$ ninja -C build/ install
+	$ cd ..
+
+Credit
+======
+
+The code base of `libxcvt` is identical to `xf86CVTMode()` therefore
+all credits for `libxcvt` go to the author (Luc Verhaegen) and
+contributors of `xf86CVTMode()` and the `cvt` utility as found in the
+[xserver](https://gitlab.freedesktop.org/xorg/xserver/) repository.

cvt/cvt.c

+/*
+ * Copyright 2005-2006 Luc Verhaegen.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR
+ * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
+ * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
+ * OTHER DEALINGS IN THE SOFTWARE.
+ *
+ */
+
+/* Standalone VESA CVT standard timing modelines generator. */
+
+#include <string.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <math.h>
+
+#include <libxcvt/libxcvt.h>
+
+bool
+cvt_is_standard(int hdisplay, int vdisplay, float vrefresh, bool reduced, bool verbose)
+{
+    bool is_cvt = true;
+
+    if ((!(vdisplay % 3) && ((vdisplay * 4 / 3) == hdisplay)) ||
+        (!(vdisplay % 9) && ((vdisplay * 16 / 9) == hdisplay)) ||
+        (!(vdisplay % 10) && ((vdisplay * 16 / 10) == hdisplay)) ||
+        (!(vdisplay % 4) && ((vdisplay * 5 / 4) == hdisplay)) ||
+        (!(vdisplay % 9) && ((vdisplay * 15 / 9) == hdisplay)));
+    else {
+        if (verbose)
+            fprintf(stderr, "Warning: Aspect Ratio is not CVT standard.\n");
+        is_cvt = false;
+    }
+
+    if ((vrefresh != 50.0) && (vrefresh != 60.0) &&
+        (vrefresh != 75.0) && (vrefresh != 85.0)) {
+        if (verbose)
+            fprintf(stderr, "Warning: Refresh Rate %.2f is not CVT standard "
+                    "(50, 60, 75 or 85Hz).\n", vrefresh);
+        is_cvt = false;
+    }
+
+    return is_cvt;
+}
+/*
+ * I'm not documenting --interlaced for obvious reasons, even though I did
+ * implement it. I also can't deny having looked at gtf here.
+ */
+static void
+print_usage(char *Name)
+{
+    fprintf(stderr, "\n");
+    fprintf(stderr, "usage: %s [-v|--verbose] [-r|--reduced] X Y [refresh]\n",
+            Name);
+    fprintf(stderr, "\n");
+    fprintf(stderr, " -v|--verbose : Warn about CVT standard adherence.\n");
+    fprintf(stderr, " -r|--reduced : Create a mode with reduced blanking "
+            "(default: normal blanking).\n");
+    fprintf(stderr, "            X : Desired horizontal resolution "
+            "(multiple of 8, required).\n");
+    fprintf(stderr,
+            "            Y : Desired vertical resolution (required).\n");
+    fprintf(stderr,
+            "      refresh : Desired refresh rate (default: 60.0Hz).\n");
+    fprintf(stderr, "\n");
+
+    fprintf(stderr, "Calculates VESA CVT (Coordinated Video Timing) modelines"
+            " for use with X.\n");
+}
+
+/*
+ *
+ */
+static void
+print_comment(struct libxcvt_mode_info *mode_info, bool is_cvt, bool reduced)
+{
+    printf("# %dx%d %.2f Hz ", mode_info->hdisplay, mode_info->vdisplay, mode_info->vrefresh);
+
+    if (is_cvt) {
+        printf("(CVT %.2fM",
+               ((float) mode_info->hdisplay * mode_info->vdisplay) / 1000000.0);
+
+        if (!(mode_info->vdisplay % 3) &&
+            ((mode_info->vdisplay * 4 / 3) == mode_info->hdisplay))
+            printf("3");
+        else if (!(mode_info->vdisplay % 9) &&
+                 ((mode_info->vdisplay * 16 / 9) == mode_info->hdisplay))
+            printf("9");
+        else if (!(mode_info->vdisplay % 10) &&
+                 ((mode_info->vdisplay * 16 / 10) == mode_info->hdisplay))
+            printf("A");
+        else if (!(mode_info->vdisplay % 4) &&
+                 ((mode_info->vdisplay * 5 / 4) == mode_info->hdisplay))
+            printf("4");
+        else if (!(mode_info->vdisplay % 9) &&
+                 ((mode_info->vdisplay * 15 / 9) == mode_info->hdisplay))
+            printf("9");
+
+        if (reduced)
+            printf("-R");
+
+        printf(") ");
+    }
+    else
+        printf("(CVT) ");
+
+    printf("hsync: %.2f kHz; ", mode_info->hsync);
+    printf("pclk: %.2f MHz", ((float) mode_info->dot_clock) / 1000.0);
+
+    printf("\n");
+}
+
+/*
+ * Originally grabbed from xf86Mode.c.
+ *
+ * Ignoring the actual mode_info->name, as the user will want something solid
+ * to grab hold of.
+ */
+static void
+print_mode_line(struct libxcvt_mode_info *mode_info, int hdisplay, int vdisplay, float vrefresh,
+              bool reduced)
+{
+    if (reduced)
+        printf("Modeline \"%dx%dR\"  ", hdisplay, vdisplay);
+    else
+        printf("Modeline \"%dx%d_%.2f\"  ", hdisplay, vdisplay, vrefresh);
+
+    printf("%6.2f  %i %i %i %i  %i %i %i %i", mode_info->dot_clock / 1000.,
+           mode_info->hdisplay, mode_info->hsync_start, mode_info->hsync_end, mode_info->htotal,
+           mode_info->vdisplay, mode_info->vsync_start, mode_info->vsync_end, mode_info->vtotal);
+
+    if (mode_info->mode_flags & LIBXCVT_MODE_FLAG_INTERLACE)
+        printf(" interlace");
+    if (mode_info->mode_flags & LIBXCVT_MODE_FLAG_HSYNC_POSITIVE)
+        printf(" +hsync");
+    if (mode_info->mode_flags & LIBXCVT_MODE_FLAG_HSYNC_NEGATIVE)
+        printf(" -hsync");
+    if (mode_info->mode_flags & LIBXCVT_MODE_FLAG_VSYNC_POSITIVE)
+        printf(" +vsync");
+    if (mode_info->mode_flags & LIBXCVT_MODE_FLAG_VSYNC_NEGATIVE)
+        printf(" -vsync");
+
+    printf("\n");
+}
+
+/*
+ *
+ */
+int
+main(int argc, char *argv[])
+{
+    struct libxcvt_mode_info *mode_info;
+    int hdisplay = 0, vdisplay = 0;
+    float vrefresh = 0.0;
+    bool reduced = false, verbose = false, is_cvt;
+    bool interlaced = false;
+    int n;
+
+    if ((argc < 3) || (argc > 7)) {
+        print_usage(argv[0]);
+        return 1;
+    }
+
+    /* This doesn't filter out bad flags properly. Bad flags get passed down
+     * to atoi/atof, which then return 0, so that these variables can get
+     * filled next time round. So this is just a cosmetic problem.
+     */
+    for (n = 1; n < argc; n++) {
+        if (!strcmp(argv[n], "-r") || !strcmp(argv[n], "--reduced"))
+            reduced = true;
+        else if (!strcmp(argv[n], "-i") || !strcmp(argv[n], "--interlaced"))
+            interlaced = true;
+        else if (!strcmp(argv[n], "-v") || !strcmp(argv[n], "--verbose"))
+            verbose = true;
+        else if (!strcmp(argv[n], "-h") || !strcmp(argv[n], "--help")) {
+            print_usage(argv[0]);
+            return 0;
+        }
+        else if (!hdisplay) {
+            hdisplay = atoi(argv[n]);
+            if (!hdisplay) {
+                print_usage(argv[0]);
+                return 1;
+            }
+        }
+        else if (!vdisplay) {
+            vdisplay = atoi(argv[n]);
+            if (!vdisplay) {
+                print_usage(argv[0]);
+                return 1;
+            }
+        }
+        else if (!vrefresh) {
+            vrefresh = atof(argv[n]);
+            if (!vrefresh) {
+                print_usage(argv[0]);
+                return 1;
+            }
+        }
+        else {
+            print_usage(argv[0]);
+            return 1;
+        }
+    }
+
+    if (!hdisplay || !vdisplay) {
+        print_usage(argv[0]);
+        return 0;
+    }
+
+    /* Default to 60.0Hz */
+    if (!vrefresh)
+        vrefresh = 60.0;
+
+    /* Horizontal timing is always a multiple of 8: round up. */
+    if (hdisplay & 0x07) {
+        hdisplay &= ~0x07;
+        hdisplay += 8;
+    }
+
+    if (reduced) {
+        if ((vrefresh / 60.0) != floor(vrefresh / 60.0)) {
+            fprintf(stderr,
+                    "\nERROR: Multiple of 60Hz refresh rate required for "
+                    " reduced blanking.\n");
+            print_usage(argv[0]);
+            return 0;
+        }
+    }
+
+    mode_info = libxcvt_gen_mode_info(hdisplay, vdisplay, vrefresh, reduced, interlaced);
+    if (!mode_info) {
+        fprintf(stderr, "Out of memory!\n");
+            return 0;
+    }
+
+    is_cvt = cvt_is_standard(hdisplay, vdisplay, vrefresh, reduced, verbose);
+    print_comment(mode_info, is_cvt, reduced);
+    print_mode_line(mode_info, hdisplay, vdisplay, vrefresh, reduced);
+    free(mode_info);
+
+    return 0;
+}

cvt/meson.build

+cvt_src = [
+	'cvt.c',
+]
+
+executable('cvt',
+	   cvt_src,
+	   include_directories : inc,
+	   link_with : libxcvt,
+	   dependencies: mdep,
+	   install : true)

include/libxcvt/libxcvt.h

+/*
+ * Copyright 2005-2006 Luc Verhaegen.
+ * Copyright © 2021 Red Hat, Inc.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR
+ * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
+ * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
+ * OTHER DEALINGS IN THE SOFTWARE.
+ *
+ */
+
+#ifndef _LIBCVT_H_
+#define _LIBCVT_H_
+
+#include <stdbool.h>
+#include <libxcvt/libxcvt_mode.h>
+
+struct libxcvt_mode_info *
+libxcvt_gen_mode_info(int   hdisplay,
+                      int   vdisplay,
+                      float vrefresh,
+                      bool  reduced,
+                      bool  interlaced);
+
+#endif /* _LIBCVT_H_ */

include/libxcvt/libxcvt_mode.h

+/*
+ * Copyright © 2000 Compaq Computer Corporation
+ * Copyright © 2002 Hewlett Packard Company
+ * Copyright © 2006 Intel Corporation
+ * Copyright © 2008, 2021 Red Hat, Inc.
+ *
+ * Permission to use, copy, modify, distribute, and sell this software and its
+ * documentation for any purpose is hereby granted without fee, provided that
+ * the above copyright notice appear in all copies and that both that copyright
+ * notice and this permission notice appear in supporting documentation, and
+ * that the name of the copyright holders not be used in advertising or
+ * publicity pertaining to distribution of the software without specific,
+ * written prior permission.  The copyright holders make no representations
+ * about the suitability of this software for any purpose.  It is provided "as
+ * is" without express or implied warranty.
+ *
+ * THE COPYRIGHT HOLDERS DISCLAIM ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
+ * INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO
+ * EVENT SHALL THE COPYRIGHT HOLDERS BE LIABLE FOR ANY SPECIAL, INDIRECT OR
+ * CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE,
+ * DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
+ * TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
+ * OF THIS SOFTWARE.
+ *
+ */
+
+#ifndef _LIBXCVT_MODE_H_
+#define _LIBXCVT_MODE_H_
+
+#include <stdint.h>
+
+/* Conveniently chosen to match the RandR definitions */
+enum  libxcvt_mode_flags {
+    LIBXCVT_MODE_FLAG_HSYNC_POSITIVE    = (1 << 0),
+    LIBXCVT_MODE_FLAG_HSYNC_NEGATIVE    = (1 << 1),
+    LIBXCVT_MODE_FLAG_VSYNC_POSITIVE    = (1 << 2),
+    LIBXCVT_MODE_FLAG_VSYNC_NEGATIVE    = (1 << 3),
+    LIBXCVT_MODE_FLAG_INTERLACE         = (1 << 4),
+};
+
+struct libxcvt_mode_info {
+    uint32_t                hdisplay;
+    uint32_t                vdisplay;
+    float                   vrefresh;
+    float                   hsync;
+    uint64_t                dot_clock;
+    uint16_t                hsync_start;
+    uint16_t                hsync_end;
+    uint16_t                htotal;
+    uint16_t                vsync_start;
+    uint16_t                vsync_end;
+    uint16_t                vtotal;
+    enum libxcvt_mode_flags mode_flags;
+};
+
+#endif /* _LIBXCVT_MODE_H_ */

include/libxcvt/meson.build

+install_headers('libxcvt.h','libxcvt_mode.h', subdir: 'libxcvt')

include/meson.build

+subdir('libxcvt')

lib/libxcvt.c

+/*
+ * Copyright 2005-2006 Luc Verhaegen.
+ * Copyright © 2021 Red Hat, Inc.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR
+ * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
+ * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
+ * OTHER DEALINGS IN THE SOFTWARE.
+ *
+ */
+
+/* Standalone VESA CVT standard timing modelines generator. */
+
+
+#include <string.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+#include <libxcvt/libxcvt.h>
+
+/*
+ * Generate a CVT standard mode from hdisplay, vdisplay and vrefresh.
+ *
+ * These calculations are stolen from the CVT calculation spreadsheet written
+ * by Graham Loveridge. He seems to be claiming no copyright and there seems to
+ * be no license attached to this. He apparently just wants to see his name
+ * mentioned.
+ *
+ * This file can be found at http://www.vesa.org/Public/CVT/CVTd6r1.xls
+ *
+ * Comments and structure corresponds to the comments and structure of the xls.
+ * This should ease importing of future changes to the standard (not very
+ * likely though).
+ *
+ * About margins; i'm sure that they are to be the bit between HDisplay and
+ * HBlankStart, HBlankEnd and HTotal, VDisplay and VBlankStart, VBlankEnd and
+ * VTotal, where the overscan colour is shown. FB seems to call _all_ blanking
+ * outside sync "margin" for some reason. Since we prefer seeing proper
+ * blanking instead of the overscan colour, and since the Crtc* values will
+ * probably get altered after us, we will disable margins altogether. With
+ * these calculations, Margins will plainly expand H/VDisplay, and we don't
+ * want that. -- libv
+ *
+ */
+struct libxcvt_mode_info *
+libxcvt_gen_mode_info(int hdisplay, int vdisplay, float vrefresh, bool reduced, bool interlaced)
+{
+    bool margins = false;
+    float vfield_rate, hperiod;
+    int hdisplay_rnd, hmargin;
+    int vdisplay_rnd, vmargin, vsync;
+    float interlace;            /* Please rename this */
+    struct libxcvt_mode_info *mode_info;
+
+    mode_info = calloc(1, sizeof *mode_info);
+    if (!mode_info)
+        return NULL;
+
+    mode_info->hdisplay = hdisplay;
+    mode_info->vdisplay = vdisplay;
+    mode_info->vrefresh = vrefresh;
+
+    /* 1) top/bottom margin size (% of height) - default: 1.8 */
+#define CVT_MARGIN_PERCENTAGE 1.8
+
+    /* 2) character cell horizontal granularity (pixels) - default 8 */
+#define CVT_H_GRANULARITY 8
+
+    /* 4) Minimum vertical porch (lines) - default 3 */
+#define CVT_MIN_V_PORCH 3
+
+    /* 4) Minimum number of vertical back porch lines - default 6 */
+#define CVT_MIN_V_BPORCH 6
+
+    /* Pixel Clock step (kHz) */
+#define CVT_CLOCK_STEP 250
+
+    /* CVT default is 60.0Hz */
+    if (!mode_info->vrefresh)
+        mode_info->vrefresh = 60.0;
+
+    /* 1. Required field rate */
+    if (interlaced)
+        vfield_rate = mode_info->vrefresh * 2;
+    else
+        vfield_rate = mode_info->vrefresh;
+
+    /* 2. Horizontal pixels */
+    hdisplay_rnd = mode_info->hdisplay - (mode_info->hdisplay % CVT_H_GRANULARITY);
+
+    /* 3. Determine left and right borders */
+    if (margins) {
+        /* right margin is actually exactly the same as left */
+        hmargin = (((float) hdisplay_rnd) * CVT_MARGIN_PERCENTAGE / 100.0);
+        hmargin -= hmargin % CVT_H_GRANULARITY;
+    }
+    else {
+        hmargin = 0;
+    }
+
+    /* 4. Find total active pixels */
+    mode_info->hdisplay = hdisplay_rnd + 2 * hmargin;
+
+    /* 5. Find number of lines per field */
+    if (interlaced)
+        vdisplay_rnd = mode_info->vdisplay / 2;
+    else
+        vdisplay_rnd = mode_info->vdisplay;
+
+    /* 6. Find top and bottom margins */
+    /* nope. */
+    if (margins)
+        /* top and bottom margins are equal again. */
+        vmargin = (((float) vdisplay_rnd) * CVT_MARGIN_PERCENTAGE / 100.0);
+    else
+        vmargin = 0;
+
+    mode_info->vdisplay = mode_info->vdisplay + 2 * vmargin;
+
+    /* 7. interlace */
+    if (interlaced)
+        interlace = 0.5;
+    else
+        interlace = 0.0;
+
+    /* Determine vsync Width from aspect ratio */
+    if (!(mode_info->vdisplay % 3) && ((mode_info->vdisplay * 4 / 3) == mode_info->hdisplay))
+        vsync = 4;
+    else if (!(mode_info->vdisplay % 9) && ((mode_info->vdisplay * 16 / 9) == mode_info->hdisplay))
+        vsync = 5;
+    else if (!(mode_info->vdisplay % 10) && ((mode_info->vdisplay * 16 / 10) == mode_info->hdisplay))
+        vsync = 6;
+    else if (!(mode_info->vdisplay % 4) && ((mode_info->vdisplay * 5 / 4) == mode_info->hdisplay))
+        vsync = 7;
+    else if (!(mode_info->vdisplay % 9) && ((mode_info->vdisplay * 15 / 9) == mode_info->hdisplay))
+        vsync = 7;
+    else                        /* Custom */
+        vsync = 10;
+
+    if (!reduced) {             /* simplified GTF calculation */
+
+        /* 4) Minimum time of vertical sync + back porch interval (µs)