/* * v4l2-dv-timings - dv-timings helper functions * * Copyright 2013 Cisco Systems, Inc. and/or its affiliates. All rights reserved. * * This program is free software; you may redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation; version 2 of the License. * * 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 AUTHORS OR COPYRIGHT HOLDERS * 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. * */ #include #include #include #include #include #include #include MODULE_AUTHOR("Hans Verkuil"); MODULE_DESCRIPTION("V4L2 DV Timings Helper Functions"); MODULE_LICENSE("GPL"); const struct v4l2_dv_timings v4l2_dv_timings_presets[] = { V4L2_DV_BT_CEA_640X480P59_94, V4L2_DV_BT_CEA_720X480I59_94, V4L2_DV_BT_CEA_720X480P59_94, V4L2_DV_BT_CEA_720X576I50, V4L2_DV_BT_CEA_720X576P50, V4L2_DV_BT_CEA_1280X720P24, V4L2_DV_BT_CEA_1280X720P25, V4L2_DV_BT_CEA_1280X720P30, V4L2_DV_BT_CEA_1280X720P50, V4L2_DV_BT_CEA_1280X720P60, V4L2_DV_BT_CEA_1920X1080P24, V4L2_DV_BT_CEA_1920X1080P25, V4L2_DV_BT_CEA_1920X1080P30, V4L2_DV_BT_CEA_1920X1080I50, V4L2_DV_BT_CEA_1920X1080P50, V4L2_DV_BT_CEA_1920X1080I60, V4L2_DV_BT_CEA_1920X1080P60, V4L2_DV_BT_DMT_640X350P85, V4L2_DV_BT_DMT_640X400P85, V4L2_DV_BT_DMT_720X400P85, V4L2_DV_BT_DMT_640X480P72, V4L2_DV_BT_DMT_640X480P75, V4L2_DV_BT_DMT_640X480P85, V4L2_DV_BT_DMT_800X600P56, V4L2_DV_BT_DMT_800X600P60, V4L2_DV_BT_DMT_800X600P72, V4L2_DV_BT_DMT_800X600P75, V4L2_DV_BT_DMT_800X600P85, V4L2_DV_BT_DMT_800X600P120_RB, V4L2_DV_BT_DMT_848X480P60, V4L2_DV_BT_DMT_1024X768I43, V4L2_DV_BT_DMT_1024X768P60, V4L2_DV_BT_DMT_1024X768P70, V4L2_DV_BT_DMT_1024X768P75, V4L2_DV_BT_DMT_1024X768P85, V4L2_DV_BT_DMT_1024X768P120_RB, V4L2_DV_BT_DMT_1152X864P75, V4L2_DV_BT_DMT_1280X768P60_RB, V4L2_DV_BT_DMT_1280X768P60, V4L2_DV_BT_DMT_1280X768P75, V4L2_DV_BT_DMT_1280X768P85, V4L2_DV_BT_DMT_1280X768P120_RB, V4L2_DV_BT_DMT_1280X800P60_RB, V4L2_DV_BT_DMT_1280X800P60, V4L2_DV_BT_DMT_1280X800P75, V4L2_DV_BT_DMT_1280X800P85, V4L2_DV_BT_DMT_1280X800P120_RB, V4L2_DV_BT_DMT_1280X960P60, V4L2_DV_BT_DMT_1280X960P85, V4L2_DV_BT_DMT_1280X960P120_RB, V4L2_DV_BT_DMT_1280X1024P60, V4L2_DV_BT_DMT_1280X1024P75, V4L2_DV_BT_DMT_1280X1024P85, V4L2_DV_BT_DMT_1280X1024P120_RB, V4L2_DV_BT_DMT_1360X768P60, V4L2_DV_BT_DMT_1360X768P120_RB, V4L2_DV_BT_DMT_1366X768P60, V4L2_DV_BT_DMT_1366X768P60_RB, V4L2_DV_BT_DMT_1400X1050P60_RB, V4L2_DV_BT_DMT_1400X1050P60, V4L2_DV_BT_DMT_1400X1050P75, V4L2_DV_BT_DMT_1400X1050P85, V4L2_DV_BT_DMT_1400X1050P120_RB, V4L2_DV_BT_DMT_1440X900P60_RB, V4L2_DV_BT_DMT_1440X900P60, V4L2_DV_BT_DMT_1440X900P75, V4L2_DV_BT_DMT_1440X900P85, V4L2_DV_BT_DMT_1440X900P120_RB, V4L2_DV_BT_DMT_1600X900P60_RB, V4L2_DV_BT_DMT_1600X1200P60, V4L2_DV_BT_DMT_1600X1200P65, V4L2_DV_BT_DMT_1600X1200P70, V4L2_DV_BT_DMT_1600X1200P75, V4L2_DV_BT_DMT_1600X1200P85, V4L2_DV_BT_DMT_1600X1200P120_RB, V4L2_DV_BT_DMT_1680X1050P60_RB, V4L2_DV_BT_DMT_1680X1050P60, V4L2_DV_BT_DMT_1680X1050P75, V4L2_DV_BT_DMT_1680X1050P85, V4L2_DV_BT_DMT_1680X1050P120_RB, V4L2_DV_BT_DMT_1792X1344P60, V4L2_DV_BT_DMT_1792X1344P75, V4L2_DV_BT_DMT_1792X1344P120_RB, V4L2_DV_BT_DMT_1856X1392P60, V4L2_DV_BT_DMT_1856X1392P75, V4L2_DV_BT_DMT_1856X1392P120_RB, V4L2_DV_BT_DMT_1920X1200P60_RB, V4L2_DV_BT_DMT_1920X1200P60, V4L2_DV_BT_DMT_1920X1200P75, V4L2_DV_BT_DMT_1920X1200P85, V4L2_DV_BT_DMT_1920X1200P120_RB, V4L2_DV_BT_DMT_1920X1440P60, V4L2_DV_BT_DMT_1920X1440P75, V4L2_DV_BT_DMT_1920X1440P120_RB, V4L2_DV_BT_DMT_2048X1152P60_RB, V4L2_DV_BT_DMT_2560X1600P60_RB, V4L2_DV_BT_DMT_2560X1600P60, V4L2_DV_BT_DMT_2560X1600P75, V4L2_DV_BT_DMT_2560X1600P85, V4L2_DV_BT_DMT_2560X1600P120_RB, V4L2_DV_BT_CEA_3840X2160P24, V4L2_DV_BT_CEA_3840X2160P25, V4L2_DV_BT_CEA_3840X2160P30, V4L2_DV_BT_CEA_3840X2160P50, V4L2_DV_BT_CEA_3840X2160P60, V4L2_DV_BT_CEA_4096X2160P24, V4L2_DV_BT_CEA_4096X2160P25, V4L2_DV_BT_CEA_4096X2160P30, V4L2_DV_BT_CEA_4096X2160P50, V4L2_DV_BT_DMT_4096X2160P59_94_RB, V4L2_DV_BT_CEA_4096X2160P60, { } }; EXPORT_SYMBOL_GPL(v4l2_dv_timings_presets); bool v4l2_valid_dv_timings(const struct v4l2_dv_timings *t, const struct v4l2_dv_timings_cap *dvcap, v4l2_check_dv_timings_fnc fnc, void *fnc_handle) { const struct v4l2_bt_timings *bt = &t->bt; const struct v4l2_bt_timings_cap *cap = &dvcap->bt; u32 caps = cap->capabilities; if (t->type != V4L2_DV_BT_656_1120) return false; if (t->type != dvcap->type || bt->height < cap->min_height || bt->height > cap->max_height || bt->width < cap->min_width || bt->width > cap->max_width || bt->pixelclock < cap->min_pixelclock || bt->pixelclock > cap->max_pixelclock || (cap->standards && !(bt->standards & cap->standards)) || (bt->interlaced && !(caps & V4L2_DV_BT_CAP_INTERLACED)) || (!bt->interlaced && !(caps & V4L2_DV_BT_CAP_PROGRESSIVE))) return false; return fnc == NULL || fnc(t, fnc_handle); } EXPORT_SYMBOL_GPL(v4l2_valid_dv_timings); int v4l2_enum_dv_timings_cap(struct v4l2_enum_dv_timings *t, const struct v4l2_dv_timings_cap *cap, v4l2_check_dv_timings_fnc fnc, void *fnc_handle) { u32 i, idx; memset(t->reserved, 0, sizeof(t->reserved)); for (i = idx = 0; v4l2_dv_timings_presets[i].bt.width; i++) { if (v4l2_valid_dv_timings(v4l2_dv_timings_presets + i, cap, fnc, fnc_handle) && idx++ == t->index) { t->timings = v4l2_dv_timings_presets[i]; return 0; } } return -EINVAL; } EXPORT_SYMBOL_GPL(v4l2_enum_dv_timings_cap); bool v4l2_find_dv_timings_cap(struct v4l2_dv_timings *t, const struct v4l2_dv_timings_cap *cap, unsigned pclock_delta, v4l2_check_dv_timings_fnc fnc, void *fnc_handle) { int i; if (!v4l2_valid_dv_timings(t, cap, fnc, fnc_handle)) return false; for (i = 0; i < v4l2_dv_timings_presets[i].bt.width; i++) { if (v4l2_valid_dv_timings(v4l2_dv_timings_presets + i, cap, fnc, fnc_handle) && v4l2_match_dv_timings(t, v4l2_dv_timings_presets + i, pclock_delta)) { *t = v4l2_dv_timings_presets[i]; return true; } } return false; } EXPORT_SYMBOL_GPL(v4l2_find_dv_timings_cap); /** * v4l2_match_dv_timings - check if two timings match * @t1 - compare this v4l2_dv_timings struct... * @t2 - with this struct. * @pclock_delta - the allowed pixelclock deviation. * * Compare t1 with t2 with a given margin of error for the pixelclock. */ bool v4l2_match_dv_timings(const struct v4l2_dv_timings *t1, const struct v4l2_dv_timings *t2, unsigned pclock_delta) { if (t1->type != t2->type || t1->type != V4L2_DV_BT_656_1120) return false; if (t1->bt.width == t2->bt.width && t1->bt.height == t2->bt.height && t1->bt.interlaced == t2->bt.interlaced && t1->bt.polarities == t2->bt.polarities && t1->bt.pixelclock >= t2->bt.pixelclock - pclock_delta && t1->bt.pixelclock <= t2->bt.pixelclock + pclock_delta && t1->bt.hfrontporch == t2->bt.hfrontporch && t1->bt.vfrontporch == t2->bt.vfrontporch && t1->bt.vsync == t2->bt.vsync && t1->bt.vbackporch == t2->bt.vbackporch && (!t1->bt.interlaced || (t1->bt.il_vfrontporch == t2->bt.il_vfrontporch && t1->bt.il_vsync == t2->bt.il_vsync && t1->bt.il_vbackporch == t2->bt.il_vbackporch))) return true; return false; } EXPORT_SYMBOL_GPL(v4l2_match_dv_timings); void v4l2_print_dv_timings(const char *dev_prefix, const char *prefix, const struct v4l2_dv_timings *t, bool detailed) { const struct v4l2_bt_timings *bt = &t->bt; u32 htot, vtot; if (t->type != V4L2_DV_BT_656_1120) return; htot = V4L2_DV_BT_FRAME_WIDTH(bt); vtot = V4L2_DV_BT_FRAME_HEIGHT(bt); if (prefix == NULL) prefix = ""; pr_info("%s: %s%ux%u%s%u (%ux%u)\n", dev_prefix, prefix, bt->width, bt->height, bt->interlaced ? "i" : "p", (htot * vtot) > 0 ? ((u32)bt->pixelclock / (htot * vtot)) : 0, htot, vtot); if (!detailed) return; pr_info("%s: horizontal: fp = %u, %ssync = %u, bp = %u\n", dev_prefix, bt->hfrontporch, (bt->polarities & V4L2_DV_HSYNC_POS_POL) ? "+" : "-", bt->hsync, bt->hbackporch); pr_info("%s: vertical: fp = %u, %ssync = %u, bp = %u\n", dev_prefix, bt->vfrontporch, (bt->polarities & V4L2_DV_VSYNC_POS_POL) ? "+" : "-", bt->vsync, bt->vbackporch); pr_info("%s: pixelclock: %llu\n", dev_prefix, bt->pixelclock); pr_info("%s: flags (0x%x):%s%s%s%s\n", dev_prefix, bt->flags, (bt->flags & V4L2_DV_FL_REDUCED_BLANKING) ? " REDUCED_BLANKING" : "", (bt->flags & V4L2_DV_FL_CAN_REDUCE_FPS) ? " CAN_REDUCE_FPS" : "", (bt->flags & V4L2_DV_FL_REDUCED_FPS) ? " REDUCED_FPS" : "", (bt->flags & V4L2_DV_FL_HALF_LINE) ? " HALF_LINE" : ""); pr_info("%s: standards (0x%x):%s%s%s%s\n", dev_prefix, bt->standards, (bt->standards & V4L2_DV_BT_STD_CEA861) ? " CEA" : "", (bt->standards & V4L2_DV_BT_STD_DMT) ? " DMT" : "", (bt->standards & V4L2_DV_BT_STD_CVT) ? " CVT" : "", (bt->standards & V4L2_DV_BT_STD_GTF) ? " GTF" : ""); } EXPORT_SYMBOL_GPL(v4l2_print_dv_timings); /* * CVT defines * Based on Coordinated Video Timings Standard * version 1.1 September 10, 2003 */ #define CVT_PXL_CLK_GRAN 250000 /* pixel clock granularity */ /* Normal blanking */ #define CVT_MIN_V_BPORCH 7 /* lines */ #define CVT_MIN_V_PORCH_RND 3 /* lines */ #define CVT_MIN_VSYNC_BP 550 /* min time of vsync + back porch (us) */ /* Normal blanking for CVT uses GTF to calculate horizontal blanking */ #define CVT_CELL_GRAN 8 /* character cell granularity */ #define CVT_M 600 /* blanking formula gradient */ #define CVT_C 40 /* blanking formula offset */ #define CVT_K 128 /* blanking formula scaling factor */ #define CVT_J 20 /* blanking formula scaling factor */ #define CVT_C_PRIME (((CVT_C - CVT_J) * CVT_K / 256) + CVT_J) #define CVT_M_PRIME (CVT_K * CVT_M / 256) /* Reduced Blanking */ #define CVT_RB_MIN_V_BPORCH 7 /* lines */ #define CVT_RB_V_FPORCH 3 /* lines */ #define CVT_RB_MIN_V_BLANK 460 /* us */ #define CVT_RB_H_SYNC 32 /* pixels */ #define CVT_RB_H_BPORCH 80 /* pixels */ #define CVT_RB_H_BLANK 160 /* pixels */ /** v4l2_detect_cvt - detect if the given timings follow the CVT standard * @frame_height - the total height of the frame (including blanking) in lines. * @hfreq - the horizontal frequency in Hz. * @vsync - the height of the vertical sync in lines. * @polarities - the horizontal and vertical polarities (same as struct * v4l2_bt_timings polarities). * @fmt - the resulting timings. * * This function will attempt to detect if the given values correspond to a * valid CVT format. If so, then it will return true, and fmt will be filled * in with the found CVT timings. * * TODO: VESA defined a new version 2 of their reduced blanking * formula. Support for that is currently missing in this CVT * detection function. */ bool v4l2_detect_cvt(unsigned frame_height, unsigned hfreq, unsigned vsync, u32 polarities, struct v4l2_dv_timings *fmt) { int v_fp, v_bp, h_fp, h_bp, hsync; int frame_width, image_height, image_width; bool reduced_blanking; unsigned pix_clk; if (vsync < 4 || vsync > 7) return false; if (polarities == V4L2_DV_VSYNC_POS_POL) reduced_blanking = false; else if (polarities == V4L2_DV_HSYNC_POS_POL) reduced_blanking = true; else return false; /* Vertical */ if (reduced_blanking) { v_fp = CVT_RB_V_FPORCH; v_bp = (CVT_RB_MIN_V_BLANK * hfreq + 1999999) / 1000000; v_bp -= vsync + v_fp; if (v_bp < CVT_RB_MIN_V_BPORCH) v_bp = CVT_RB_MIN_V_BPORCH; } else { v_fp = CVT_MIN_V_PORCH_RND; v_bp = (CVT_MIN_VSYNC_BP * hfreq + 1999999) / 1000000 - vsync; if (v_bp < CVT_MIN_V_BPORCH) v_bp = CVT_MIN_V_BPORCH; } image_height = (frame_height - v_fp - vsync - v_bp + 1) & ~0x1; /* Aspect ratio based on vsync */ switch (vsync) { case 4: image_width = (image_height * 4) / 3; break; case 5: image_width = (image_height * 16) / 9; break; case 6: image_width = (image_height * 16) / 10; break; case 7: /* special case */ if (image_height == 1024) image_width = (image_height * 5) / 4; else if (image_height == 768) image_width = (image_height * 15) / 9; else return false; break; default: return false; } image_width = image_width & ~7; /* Horizontal */ if (reduced_blanking) { pix_clk = (image_width + CVT_RB_H_BLANK) * hfreq; pix_clk = (pix_clk / CVT_PXL_CLK_GRAN) * CVT_PXL_CLK_GRAN; h_bp = CVT_RB_H_BPORCH; hsync = CVT_RB_H_SYNC; h_fp = CVT_RB_H_BLANK - h_bp - hsync; frame_width = image_width + CVT_RB_H_BLANK; } else { unsigned ideal_duty_cycle_per_myriad = 100 * CVT_C_PRIME - (CVT_M_PRIME * 100000) / hfreq; int h_blank; if (ideal_duty_cycle_per_myriad < 2000) ideal_duty_cycle_per_myriad = 2000; h_blank = image_width * ideal_duty_cycle_per_myriad / (10000 - ideal_duty_cycle_per_myriad); h_blank = (h_blank / (2 * CVT_CELL_GRAN)) * 2 * CVT_CELL_GRAN; pix_clk = (image_width + h_blank) * hfreq; pix_clk = (pix_clk / CVT_PXL_CLK_GRAN) * CVT_PXL_CLK_GRAN; h_bp = h_blank / 2; frame_width = image_width + h_blank; hsync = (frame_width * 8 + 50) / 100; hsync = hsync - hsync % CVT_CELL_GRAN; h_fp = h_blank - hsync - h_bp; } fmt->type = V4L2_DV_BT_656_1120; fmt->bt.polarities = polarities; fmt->bt.width = image_width; fmt->bt.height = image_height; fmt->bt.hfrontporch = h_fp; fmt->bt.vfrontporch = v_fp; fmt->bt.hsync = hsync; fmt->bt.vsync = vsync; fmt->bt.hbackporch = frame_width - image_width - h_fp - hsync; fmt->bt.vbackporch = frame_height - image_height - v_fp - vsync; fmt->bt.pixelclock = pix_clk; fmt->bt.standards = V4L2_DV_BT_STD_CVT; if (reduced_blanking) fmt->bt.flags |= V4L2_DV_FL_REDUCED_BLANKING; return true; } EXPORT_SYMBOL_GPL(v4l2_detect_cvt); /* * GTF defines * Based on Generalized Timing Formula Standard * Version 1.1 September 2, 1999 */ #define GTF_PXL_CLK_GRAN 250000 /* pixel clock granularity */ #define GTF_MIN_VSYNC_BP 550 /* min time of vsync + back porch (us) */ #define GTF_V_FP 1 /* vertical front porch (lines) */ #define GTF_CELL_GRAN 8 /* character cell granularity */ /* Default */ #define GTF_D_M 600 /* blanking formula gradient */ #define GTF_D_C 40 /* blanking formula offset */ #define GTF_D_K 128 /* blanking formula scaling factor */ #define GTF_D_J 20 /* blanking formula scaling factor */ #define GTF_D_C_PRIME ((((GTF_D_C - GTF_D_J) * GTF_D_K) / 256) + GTF_D_J) #define GTF_D_M_PRIME ((GTF_D_K * GTF_D_M) / 256) /* Secondary */ #define GTF_S_M 3600 /* blanking formula gradient */ #define GTF_S_C 40 /* blanking formula offset */ #define GTF_S_K 128 /* blanking formula scaling factor */ #define GTF_S_J 35 /* blanking formula scaling factor */ #define GTF_S_C_PRIME ((((GTF_S_C - GTF_S_J) * GTF_S_K) / 256) + GTF_S_J) #define GTF_S_M_PRIME ((GTF_S_K * GTF_S_M) / 256) /** v4l2_detect_gtf - detect if the given timings follow the GTF standard * @frame_height - the total height of the frame (including blanking) in lines. * @hfreq - the horizontal frequency in Hz. * @vsync - the height of the vertical sync in lines. * @polarities - the horizontal and vertical polarities (same as struct * v4l2_bt_timings polarities). * @aspect - preferred aspect ratio. GTF has no method of determining the * aspect ratio in order to derive the image width from the * image height, so it has to be passed explicitly. Usually * the native screen aspect ratio is used for this. If it * is not filled in correctly, then 16:9 will be assumed. * @fmt - the resulting timings. * * This function will attempt to detect if the given values correspond to a * valid GTF format. If so, then it will return true, and fmt will be filled * in with the found GTF timings. */ bool v4l2_detect_gtf(unsigned frame_height, unsigned hfreq, unsigned vsync, u32 polarities, struct v4l2_fract aspect, struct v4l2_dv_timings *fmt) { int pix_clk; int v_fp, v_bp, h_fp, hsync; int frame_width, image_height, image_width; bool default_gtf; int h_blank; if (vsync != 3) return false; if (polarities == V4L2_DV_VSYNC_POS_POL) default_gtf = true; else if (polarities == V4L2_DV_HSYNC_POS_POL) default_gtf = false; else return false; /* Vertical */ v_fp = GTF_V_FP; v_bp = (GTF_MIN_VSYNC_BP * hfreq + 999999) / 1000000 - vsync; image_height = (frame_height - v_fp - vsync - v_bp + 1) & ~0x1; if (aspect.numerator == 0 || aspect.denominator == 0) { aspect.numerator = 16; aspect.denominator = 9; } image_width = ((image_height * aspect.numerator) / aspect.denominator); image_width = (image_width + GTF_CELL_GRAN/2) & ~(GTF_CELL_GRAN - 1); /* Horizontal */ if (default_gtf) h_blank = ((image_width * GTF_D_C_PRIME * hfreq) - (image_width * GTF_D_M_PRIME * 1000) + (hfreq * (100 - GTF_D_C_PRIME) + GTF_D_M_PRIME * 1000) / 2) / (hfreq * (100 - GTF_D_C_PRIME) + GTF_D_M_PRIME * 1000); else h_blank = ((image_width * GTF_S_C_PRIME * hfreq) - (image_width * GTF_S_M_PRIME * 1000) + (hfreq * (100 - GTF_S_C_PRIME) + GTF_S_M_PRIME * 1000) / 2) / (hfreq * (100 - GTF_S_C_PRIME) + GTF_S_M_PRIME * 1000); h_blank = h_blank - h_blank % (2 * GTF_CELL_GRAN); frame_width = image_width + h_blank; pix_clk = (image_width + h_blank) * hfreq; pix_clk = pix_clk / GTF_PXL_CLK_GRAN * GTF_PXL_CLK_GRAN; hsync = (frame_width * 8 + 50) / 100; hsync = hsync - hsync % GTF_CELL_GRAN; h_fp = h_blank / 2 - hsync; fmt->type = V4L2_DV_BT_656_1120; fmt->bt.polarities = polarities; fmt->bt.width = image_width; fmt->bt.height = image_height; fmt->bt.hfrontporch = h_fp; fmt->bt.vfrontporch = v_fp; fmt->bt.hsync = hsync; fmt->bt.vsync = vsync; fmt->bt.hbackporch = frame_width - image_width - h_fp - hsync; fmt->bt.vbackporch = frame_height - image_height - v_fp - vsync; fmt->bt.pixelclock = pix_clk; fmt->bt.standards = V4L2_DV_BT_STD_GTF; if (!default_gtf) fmt->bt.flags |= V4L2_DV_FL_REDUCED_BLANKING; return true; } EXPORT_SYMBOL_GPL(v4l2_detect_gtf); /** v4l2_calc_aspect_ratio - calculate the aspect ratio based on bytes * 0x15 and 0x16 from the EDID. * @hor_landscape - byte 0x15 from the EDID. * @vert_portrait - byte 0x16 from the EDID. * * Determines the aspect ratio from the EDID. * See VESA Enhanced EDID standard, release A, rev 2, section 3.6.2: * "Horizontal and Vertical Screen Size or Aspect Ratio" */ struct v4l2_fract v4l2_calc_aspect_ratio(u8 hor_landscape, u8 vert_portrait) { struct v4l2_fract aspect = { 16, 9 }; u32 tmp; u8 ratio; /* Nothing filled in, fallback to 16:9 */ if (!hor_landscape && !vert_portrait) return aspect; /* Both filled in, so they are interpreted as the screen size in cm */ if (hor_landscape && vert_portrait) { aspect.numerator = hor_landscape; aspect.denominator = vert_portrait; return aspect; } /* Only one is filled in, so interpret them as a ratio: (val + 99) / 100 */ ratio = hor_landscape | vert_portrait; /* Change some rounded values into the exact aspect ratio */ if (ratio == 79) { aspect.numerator = 16; aspect.denominator = 9; } else if (ratio == 34) { aspect.numerator = 4; aspect.denominator = 3; } else if (ratio == 68) { aspect.numerator = 15; aspect.denominator = 9; } else { aspect.numerator = hor_landscape + 99; aspect.denominator = 100; } if (hor_landscape) return aspect; /* The aspect ratio is for portrait, so swap numerator and denominator */ tmp = aspect.denominator; aspect.denominator = aspect.numerator; aspect.numerator = tmp; return aspect; } EXPORT_SYMBOL_GPL(v4l2_calc_aspect_ratio);