diff options
Diffstat (limited to 'src/lib/edid.c')
| -rw-r--r-- | src/lib/edid.c | 35 |
1 files changed, 31 insertions, 4 deletions
diff --git a/src/lib/edid.c b/src/lib/edid.c index 76867c7..800ebdd 100644 --- a/src/lib/edid.c +++ b/src/lib/edid.c @@ -35,45 +35,72 @@ 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)) +#define __m(value) (this->edid[index++] != value) int error = 0; int checksum = 0; - size_t i; + size_t i, index = 0; + /* If the length of the EDID is not 128 bytes, we know that it is not of + EDID structure revision 1.3, and thus we do not support it. Additionally + this make sure we do not do segmentation violation on the next test. */ 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)) + /* Check that the magic number of that of the EDID structure. */ + else if (__m(0x00) || __m(0xFF) || __m(0xFF) || __m(0xFF) || __m(0xFF) || __m(0xFF) || __m(0xFF) || __m(0x00)) error = LIBGAMMA_EDID_WRONG_MAGIC_NUMBER; + /* Check that EDID structure revision 1.3 is used, it is the only version + we support. It is also by far the most commonly use revision and it is + currently the newest revision. */ else if (__test_version(this->edid, 1, 3) == 0) error = LIBGAMMA_EDID_REVISION_UNSUPPORTED; + /* If we have encountered an error, report it for the fields that require + the EDID to be parsed. Note that it is not stored for the EDID field + itself because it is not considered an error just because we do not + support the used version. */ this->width_mm_edid_error = this->height_mm_edid_error = this->gamma_error = error; + /* Retrieve the size of the viewport. This is done even if it is not + requested because it is not worth it branch. */ this->width_mm_edid = (size_t)(this->edid[21]) * 10; this->height_mm_edid = (size_t)(this->edid[22]) * 10; + /* Retrieve the monitor's gamma characteristics. */ if ((fields & LIBGAMMA_CRTC_INFO_GAMMA) && (error == 0)) { if (this->edid[23] == 0xFF) + /* If the gamma charactistics is FFh (3,55) it should be interpreted as not specified. */ 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 not error has occurred, calculate and test the checksum. + It is not considered an error that the gamma characteristics + is left unspecified in the EDID. */ if (error == 0) for (i = 0; i < this->edid_length; i++) checksum += (int)(this->edid[i]); + /* The checksum should be zero. */ if ((checksum & 255)) { + /* Store the error in all fields that require the EDID to be parsed, + as well as the EDID field itself. */ error = LIBGAMMA_EDID_CHECKSUM_ERROR; this->edid_error = this->width_mm_edid_error = this->height_mm_edid_error = error; + /* If the gamma characteristics is not specified, that is kept, + and the checksum error is augmented. */ this->gamma_error = this->gamma_error == LIBGAMMA_GAMMA_NOT_SPECIFIED - ? LIBGAMMA_GAMMA_NOT_SPECIFIED_AND_EDID_CHECKSUM_ERROR : 0; + ? LIBGAMMA_GAMMA_NOT_SPECIFIED_AND_EDID_CHECKSUM_ERROR : error; } + /* Return whether or not we encountered an error or if + the gamma characteristics was requested but is not + specified in the monitor's EDID. */ return error | this->gamma_error; +#undef __m #undef __test_version } |