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Dell
Does not support DDC.
As reported by user @w8jcik:
When used together with an Intel GPU, the source code of i915 module needs to be modified to reduce the speed of I2C from 100 kHz to 50 kHz. It is of course highly impractical to build own kernel for this purpose, but the communication fails with the default speed.
For details: see https://github.com/rockowitz/ddcutil/issues/424
VCP version: 2.0
Controller Manufacturer: Genesis
Controller Model: mh=0xff, ml=0xff, sh=0x4a
Firmware version: 29.1
Cannot set brightness less than 30. setvcp values in the range 0..50 are mapped to the range 30..50
User eskampie created the following table.
| Requested setvcp value | Observed OSD value |
|---|---|
| 0 | 30 |
| 10 | 34 |
| 20 | 38 |
| 30 | 42 |
| 40 | 46 |
| 50 | 50 |
| 60 | 60 |
| 70 | 70 |
| 80 | 80 |
| 90 | 90 |
| 100 | 100 |
VCP Version: 2.2
Controller Manufacturer: manufacturer designed (sl=0xff)
Controller Model: mh=0x01 ml=0x08 sh=0x04
Firmware version: 4.133
Manufacture year: 2017
Feature x0B: Color temperature increment: unsupported
Feature x0C: Color temperature request: unsupported
Reading unsupported feature 0x00 returns normally, with ml=ml=sh=sl=0. The unsupported feature bit is not set. Reading any other unsupported feature value results in an IOCTL failure with Linux errno=EIO (5).
VCP version: 2.1
Controller Manufacturer: Mstar
Controller Model: mh=x00, ml=x00, sh=x56
Firmware version: 1.1
Manufacture year: 2011
Lots of I2C errors. Heavily dependant on retries. The CAPABILITIES command sometimes fails, even with maximum retries. More recently, works with nouveau driver, but fails with proprietary Nvidia driver.
Reports VCP code 0B (color temperature increment) as 1 degree Kelvin, which makes the GETVCP response to VCP code 0C (color temperature request) nonsensical.
VCP version: 2.1
Controller Manufacturer: Mstar (sl=x05)
Controller Model: mh=x00, ml=x00,x sh=x56
Firmware version: 2.1
Manufacture year: 2015
Feature x0B, Color temperature increment: unsupported
Feature x0C, Color temperature request: unsupported
very clean, no DDC retries needed
VCP version: 2.1 Controller Manufacturer: RealTek (sl=0x09) Controller Model: mh=0x00, ml=0x27, sh=0x17 Firmware version: 65.3 Manufacture year: 2021
Github user Noctivans has posted extensive notes detailing what he discovered on how to control Picture In Picture/Picture By Picture using undocumented features.
VCP version: 2.1
Controller Manufacturer: STMicroelectronics (sl=x0d)
Controller Model: mh=x00, ml=x93, sh=x01
Firmware version: 2.1
Manufacture year: 2013
This monitor has a hardware LUT, however LUT loading not supported using standard VCP feature codes.
Responds to VCP feature xc0 (Display Usage Time), but returns 0.
Color temperature:
color temp increment (feature 0B): unsupported
color temp request (feature 0C): unsupported
VCP Version: 2,1
Controller Manufacturer: MStar
Controller Model: mh=0x00, ml=0x00, sh=0x56
Firmware version: 2.1
Manufacture year: 2018
Features 0B, 0C are unsupported.
Attempting to set feature x12 (contrast) less than 25 results in a value of 25. However, it is possible to set a lower contrast value in the OSD .
Unlike the Dell 2404wfp feature x10 (brightness) can be set to any value between 0..100.
Clean implementation, no I2c retries required.
As reported by user @w8jcik:
DDC is only reliable when connected to display's DisplayPort. USB to DisplayPort adapter is also fine.
Justification: I have tried HDMI-DVI passive adapter, DisplayPort-DVI passive adapter and direct HDMI-HDMI connection. Both adapters are not able to communicate over DDC. HDMI-HDMI is sometimes able to retrieve the brightness but rarely. The conclusion that the display is at fault comes from the fact that the same adapters, connectors and the PC work with other displays offering DDC, just not with U2711. The issue experienced on Intel integrated GPU Iris Pro Graphics 580 (SKL GT4), but it is most likely GPU independent.
As reported by user @rnwst:
ddcutil didn't recognize my second display, which was the second/last display in a USB-C MST setup. The first display is a Dell U2723QE. This was despite my user having read-write permissions for all i2c devices, and the i2c-dev kernel module being loaded.
The solution turned out to be a setting in the OSD menu of the Dell U2723QE. 'Display' -> 'Multi-Monitor Sync' was turned on. Once it was turned off, everything worked correctly.
VCP version: 2.1
Controller manufacturer: Mstar
Controller Model: mh=x00, ml=x94, sh=x85
Firmware version: 1.5
Manufacture year: 2012
If a value is set using SETVCP, the new value takes effect and may appear in the on-screen display. However, GETVCP (or the verification option) sometimes still retieves the old value, not the new one. More specifically:
| Feature Name | Code | Notes |
|---|---|---|
| Contrast | x12 | values below x25 take effect but the old value is returned |
| Video Gain: Red | x16 | Values below 100 take effect, but the GETVCP reports 100 |
| Video Gain: Green | x18 | Ditto |
| Video Gain: Blue | x1a | Ditto |
| Display Mode | xdc |
Reports VCP code x0B (color temperature increment) as 1 degree Kelvin, which makes the GETVCP response to VCP code x0C (color temperature request) nonsensical.
Color temperature:
color temp increment (feature 0B): 1 deg K
color temp request (feature 0C): 2
calculated color temp = 3000 + (x0c_val * x0b_val) = 3000 + (1 * 2) = 3002 degrees Kelvin
VCP version: 2.1
Controller manufacturer: Realtek (sl=x09)
Controller Model: mh=x00, ml=x11, sh=x11
Firmware version: 65.1
Manufacture year: 2015
Neither feature 0B (color temperature increment) or 0C (color temperature request) are listed in the capabilities string. However, querying feature 0B does work. Querying feature 0C fails.
Color temperature:
color temp increment (feature 0B): 100 deg K
color temp request (feature 0C): query fails
VCP version: 2.1
Controller Manufacturer: RealTek
Controller Model: mh=0x00, ml=0x11, sh=0x11
Firmware version: 65.1
Manufacture year: 2017
Fails to set the Unsupported VCP Code bit in the getvcp response packet for unsupported features.