Could help me understand some code in the Linux kernel

Where in the datasheet describes paramtry margin_left, margin_right, hsync,
_yres, margin_top, margin_bottom, vsync
for example take
_LCD_DECLARE(
            7,            /* The 3.5 is quite fast */
            240, 21, 25, 6,     /* x timing */
            320, 2, 4, 2,        /* y timing */
            40),            /* refresh rate */
datasheet http://www.friendlyarm.net/dl.php?file=TD035STED4.pdf
and
    [5] = {
        _LCD_DECLARE(
            7,
            240, 1, 26, 5,     /* x timing */
            320, 1, 5, 9,        /* y timing */
            60),            /* refresh rate */
datasheet http://www.friendlyarm.net/dl.php?file=NL4827HC19.pdf

For the TD035STED4 you can find the timing spec on page 13.
margin_left=horizontal back porch
margin_right=horizontal front porch
xres=horizontal active area
hsync=horizontal sync pulse width
and so on...

But horizontal front porch in datasheet = 10 and horizontal sync pulse
width = 10
In config
LCD_DECLARE(
            7,            /* The 3.5 is quite fast */
            240, 21, 25, 6,  /* xres, margin_right, margin_left, hsync */
            320, 2, 4, 2,     /* yres, margin_top, margin_bottom, vsync */
            40),            /* refresh rate */
That is, horizontal front porch = 25 and horizontal sync pulse width = 6

Then you should ask the author why she/he use different values