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authorMattias Andrée <maandree@operamail.com>2014-06-01 02:00:16 +0200
committerMattias Andrée <maandree@operamail.com>2014-06-01 02:00:16 +0200
commitcba9a65ed4157417b84f2d3e9b912f315a45c584 (patch)
tree4ad75a9d1f4f5bd0aff86a4d13726ef76fb4c7fe /src/lib/edid.c
parentwhitespace (diff)
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m + doc
Signed-off-by: Mattias Andrée <maandree@operamail.com>
Diffstat (limited to 'src/lib/edid.c')
-rw-r--r--src/lib/edid.c35
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
}