in fbdev/vga16fb.c [331:534]
static int vga16fb_check_var(struct fb_var_screeninfo *var,
struct fb_info *info)
{
struct vga16fb_par *par = info->par;
u32 xres, right, hslen, left, xtotal;
u32 yres, lower, vslen, upper, ytotal;
u32 vxres, xoffset, vyres, yoffset;
u32 pos;
u8 r7, rMode;
int shift;
int mode;
u32 maxmem;
par->pel_msk = 0xFF;
if (var->bits_per_pixel == 4) {
if (var->nonstd) {
if (!par->isVGA)
return -EINVAL;
shift = 3;
mode = MODE_SKIP4 | MODE_CFB;
maxmem = 16384;
par->pel_msk = 0x0F;
} else {
shift = 3;
mode = 0;
maxmem = 65536;
}
} else if (var->bits_per_pixel == 8) {
if (!par->isVGA)
return -EINVAL; /* no support on EGA */
shift = 2;
if (var->nonstd) {
mode = MODE_8BPP | MODE_CFB;
maxmem = 65536;
} else {
mode = MODE_SKIP4 | MODE_8BPP | MODE_CFB;
maxmem = 16384;
}
} else
return -EINVAL;
xres = (var->xres + 7) & ~7;
vxres = (var->xres_virtual + 0xF) & ~0xF;
xoffset = (var->xoffset + 7) & ~7;
left = (var->left_margin + 7) & ~7;
right = (var->right_margin + 7) & ~7;
hslen = (var->hsync_len + 7) & ~7;
if (vxres < xres)
vxres = xres;
if (xres + xoffset > vxres)
xoffset = vxres - xres;
var->xres = xres;
var->right_margin = right;
var->hsync_len = hslen;
var->left_margin = left;
var->xres_virtual = vxres;
var->xoffset = xoffset;
xres >>= shift;
right >>= shift;
hslen >>= shift;
left >>= shift;
vxres >>= shift;
xtotal = xres + right + hslen + left;
if (xtotal >= 256)
FAIL("xtotal too big");
if (hslen > 32)
FAIL("hslen too big");
if (right + hslen + left > 64)
FAIL("hblank too big");
par->crtc[VGA_CRTC_H_TOTAL] = xtotal - 5;
par->crtc[VGA_CRTC_H_BLANK_START] = xres - 1;
par->crtc[VGA_CRTC_H_DISP] = xres - 1;
pos = xres + right;
par->crtc[VGA_CRTC_H_SYNC_START] = pos;
pos += hslen;
par->crtc[VGA_CRTC_H_SYNC_END] = pos & 0x1F;
pos += left - 2; /* blank_end + 2 <= total + 5 */
par->crtc[VGA_CRTC_H_BLANK_END] = (pos & 0x1F) | 0x80;
if (pos & 0x20)
par->crtc[VGA_CRTC_H_SYNC_END] |= 0x80;
yres = var->yres;
lower = var->lower_margin;
vslen = var->vsync_len;
upper = var->upper_margin;
vyres = var->yres_virtual;
yoffset = var->yoffset;
if (yres > vyres)
vyres = yres;
if (vxres * vyres > maxmem) {
vyres = maxmem / vxres;
if (vyres < yres)
return -ENOMEM;
}
if (yoffset + yres > vyres)
yoffset = vyres - yres;
var->yres = yres;
var->lower_margin = lower;
var->vsync_len = vslen;
var->upper_margin = upper;
var->yres_virtual = vyres;
var->yoffset = yoffset;
if (var->vmode & FB_VMODE_DOUBLE) {
yres <<= 1;
lower <<= 1;
vslen <<= 1;
upper <<= 1;
}
ytotal = yres + lower + vslen + upper;
if (ytotal > 1024) {
ytotal >>= 1;
yres >>= 1;
lower >>= 1;
vslen >>= 1;
upper >>= 1;
rMode = 0x04;
} else
rMode = 0x00;
if (ytotal > 1024)
FAIL("ytotal too big");
if (vslen > 16)
FAIL("vslen too big");
par->crtc[VGA_CRTC_V_TOTAL] = ytotal - 2;
r7 = 0x10; /* disable linecompare */
if (ytotal & 0x100) r7 |= 0x01;
if (ytotal & 0x200) r7 |= 0x20;
par->crtc[VGA_CRTC_PRESET_ROW] = 0;
par->crtc[VGA_CRTC_MAX_SCAN] = 0x40; /* 1 scanline, no linecmp */
if (var->vmode & FB_VMODE_DOUBLE)
par->crtc[VGA_CRTC_MAX_SCAN] |= 0x80;
par->crtc[VGA_CRTC_CURSOR_START] = 0x20;
par->crtc[VGA_CRTC_CURSOR_END] = 0x00;
if ((mode & (MODE_CFB | MODE_8BPP)) == MODE_CFB)
xoffset--;
pos = yoffset * vxres + (xoffset >> shift);
par->crtc[VGA_CRTC_START_HI] = pos >> 8;
par->crtc[VGA_CRTC_START_LO] = pos & 0xFF;
par->crtc[VGA_CRTC_CURSOR_HI] = 0x00;
par->crtc[VGA_CRTC_CURSOR_LO] = 0x00;
pos = yres - 1;
par->crtc[VGA_CRTC_V_DISP_END] = pos & 0xFF;
par->crtc[VGA_CRTC_V_BLANK_START] = pos & 0xFF;
if (pos & 0x100)
r7 |= 0x0A; /* 0x02 -> DISP_END, 0x08 -> BLANK_START */
if (pos & 0x200) {
r7 |= 0x40; /* 0x40 -> DISP_END */
par->crtc[VGA_CRTC_MAX_SCAN] |= 0x20; /* BLANK_START */
}
pos += lower;
par->crtc[VGA_CRTC_V_SYNC_START] = pos & 0xFF;
if (pos & 0x100)
r7 |= 0x04;
if (pos & 0x200)
r7 |= 0x80;
pos += vslen;
par->crtc[VGA_CRTC_V_SYNC_END] = (pos & 0x0F) & ~0x10; /* disabled IRQ */
pos += upper - 1; /* blank_end + 1 <= ytotal + 2 */
par->crtc[VGA_CRTC_V_BLANK_END] = pos & 0xFF; /* 0x7F for original VGA,
but some SVGA chips requires all 8 bits to set */
if (vxres >= 512)
FAIL("vxres too long");
par->crtc[VGA_CRTC_OFFSET] = vxres >> 1;
if (mode & MODE_SKIP4)
par->crtc[VGA_CRTC_UNDERLINE] = 0x5F; /* 256, cfb8 */
else
par->crtc[VGA_CRTC_UNDERLINE] = 0x1F; /* 16, vgap */
par->crtc[VGA_CRTC_MODE] = rMode | ((mode & MODE_TEXT) ? 0xA3 : 0xE3);
par->crtc[VGA_CRTC_LINE_COMPARE] = 0xFF;
par->crtc[VGA_CRTC_OVERFLOW] = r7;
par->vss = 0x00; /* 3DA */
par->misc = 0xE3; /* enable CPU, ports 0x3Dx, positive sync */
if (var->sync & FB_SYNC_HOR_HIGH_ACT)
par->misc &= ~0x40;
if (var->sync & FB_SYNC_VERT_HIGH_ACT)
par->misc &= ~0x80;
par->mode = mode;
if (mode & MODE_8BPP)
/* pixel clock == vga clock / 2 */
vga16fb_clock_chip(par, &var->pixclock, info, 1, 2);
else
/* pixel clock == vga clock */
vga16fb_clock_chip(par, &var->pixclock, info, 1, 1);
var->red.offset = var->green.offset = var->blue.offset =
var->transp.offset = 0;
var->red.length = var->green.length = var->blue.length =
(par->isVGA) ? 6 : 2;
var->transp.length = 0;
var->activate = FB_ACTIVATE_NOW;
var->height = -1;
var->width = -1;
var->accel_flags = 0;
return 0;
}