On Fri, Dec 24, 2010 at 7:14 AM, Kai-Uwe Behrmann <[email protected]> wrote: > Am 23.12.10, 11:09 -0500 schrieb Alex Deucher: >> >> On Thu, Dec 23, 2010 at 2:25 AM, Kai-Uwe Behrmann <[email protected]> wrote: >>> >>> Hello, >>> >>> I try to talk to LVDS and DP connected displays over the i2c bus. What >>> works >>> nicely for external DVI displays appears silent for the internal one and >>> DP. >>> Any pointer what could be used or what shall be done to get a >>> communication? >>> >>> example code for EDID fetching: >>> /* 1. select i2c-dev node */ >>> const char * device_name = "/dev/i2c-0"; >>> /* 2. open device node */ >>> int fd = open( device_name, O_RDWR ); >>> /* 3. set adress */ >>> ioctl(fd, I2C_SLAVE, 0x50) >>> >>> /* 4. request desired block */ >>> usleep(50000); >>> char bits[128] = {0}; >>> int ret = write( fd, &bits, 1 ); >>> if(ret == 1) >>> { >>> /* 5. read data from node */ >>> char data[128]; >>> usleep(50000); >>> ret = read( fd, &data, 128 ); >>> } >>> >>> Already point 4 fails )-1) with a LVDS i2c node. >>> The DP port returns arbitrary data in point 5. >>> >>> The DP is on a nvidia card, LVDS seems good on nvidia but not working on >>> a >>> evergreen. >>> >> >> For radeon, make sure you are using at least 2.6.34, as previous >> kernels did not expose i2c buses properly due to missing pre/post_xfer >> i2c bit algo hooks. Next, make sure you are opening the correct i2c > > 2.6.35 worked nicely. Thanks for the tip. > >> bus. On radeons, we expose all of the on board i2c buses. In most >> cases, each connector uses a different i2c bus and there are >> additional buses for thermal chips and fan controllers, etc. Finally, > > I check the return values in the code above and the received EDID header. > >> not all oems implement an EDID for the laptop panels, or in some cases >> the EDID image is stored in the vbios. If you just want the EDID, you >> can query that using randr or via sysfs. > > For xrandr people seem to have to wait until the KMS patch is not rejecting > for wrong checksum. sysfs looks interessting too.
Yeah, that should be changed or at least an option provided to not reject them. Alex > >> Alex > > > kind regards > Kai-Uwe Behrmann > -- > developing for colour management www.behrmann.name + www.oyranos.org > _______________________________________________ [email protected]: X.Org support Archives: http://lists.freedesktop.org/archives/xorg Info: http://lists.freedesktop.org/mailman/listinfo/xorg Your subscription address: [email protected]
