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-rw-r--r--src/edid.c79
1 files changed, 79 insertions, 0 deletions
diff --git a/src/edid.c b/src/edid.c
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+/**
+ * libgamma — Display server abstraction layer for gamma ramp adjustments
+ * Copyright © 2014 Mattias Andrée (maandree@member.fsf.org)
+ *
+ * This library is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this library. If not, see <http://www.gnu.org/licenses/>.
+ */
+#include "edid.h"
+
+#include "libgamma-method.h"
+#include "libgamma-error.h"
+
+#include <stdint.h>
+
+
+/**
+ * Parse the EDID of a monitor
+ *
+ * @param this Instance of a data structure to fill with the information about the EDID.
+ * It must contain the EDID and its length.
+ * @param feilds OR:ed identifiers for the information about the EDID that should be parsed.
+ * Fields that do not have to do with EDID are ignored.
+ * @return Non-zero on error
+ */
+int libgamma_parse_edid(libgamma_crtc_information_t* restrict this, int32_t fields)
+{
+#define __test_version(edid, major, minor) (((edid)[18] == major) && ((edid)[19] == minor))
+
+ int error = 0;
+ int checksum = 0;
+ size_t i;
+
+ if (this->edid_length != 128)
+ error = LIBGAMMA_EDID_LENGTH_UNSUPPORTED;
+ else if ((this->edid[0] != 0x00) || (this->edid[1] != 0xFF) || (this->edid[2] != 0xFF) || (this->edid[3] != 0xFF) ||
+ (this->edid[4] != 0xFF) || (this->edid[5] != 0xFF) || (this->edid[6] != 0xFF) || (this->edid[7] != 0x00))
+ error = LIBGAMMA_EDID_WRONG_MAGIC_NUMBER;
+ else if (__test_version(this->edid, 1, 3) == 0)
+ error = LIBGAMMA_EDID_REVISION_UNSUPPORTED;
+
+ this->width_mm_edid_error = this->height_mm_edid_error = this->gamma_error = error;
+
+ this->width_mm_edid = (size_t)(this->edid[21]) * 10;
+ this->height_mm_edid = (size_t)(this->edid[22]) * 10;
+
+ if ((fields & CRTC_INFO_GAMMA) && (error == 0))
+ {
+ if (this->edid[23] == 0xFF)
+ this->gamma_error = LIBGAMMA_GAMMA_NOT_SPECIFIED;
+ else
+ this->gamma_red = this->gamma_green = this->gamma_blue = (float)((int)(this->edid[23]) + 100) / 100.f;
+ }
+
+ if (error == 0)
+ for (i = 0; i < this->edid_length; i++)
+ checksum += (int)(this->edid[i]);
+ if ((checksum & 255))
+ {
+ error = LIBGAMMA_EDID_CHECKSUM_ERROR;
+ this->edid_error = this->width_mm_edid_error = this->height_mm_edid_error = error;
+ this->gamma_error = this->gamma_error == LIBGAMMA_GAMMA_NOT_SPECIFIED
+ ? LIBGAMMA_GAMMA_NOT_SPECIFIED_AND_EDID_CHECKSUM_ERROR : 0;
+ }
+
+ return error | this->gamma_error;
+
+#undef __test_version
+}
+