Hello. Apologies if this thread is redundant, but I'm looking for a sanity check after spending a day trying various combinations with no success.
I have the following configuration:
* Raspberry Pi 4B
* 7" Touch Display 2
* SmartiPi Touch Pro 3 — case uses a landscape orientation
* HDMI-connected KVM
* CRT attached via RGBerry SCART HAT
* Debian 13 Trixie with updates applied
I am intending to use the 7" Touch Display 2 as a text console for running RetroPie on an external CRT via the RGBerry SCART HAT. Most of my hardware is on a KVM switch "network," and I'd like to mirror the Touch Display 2 at its 720 × 1280 native resolution as using a larger-than-7" display is often more desirable.
Unfortunately, no matter what settings I used in cmdline.txt and/or config.txt, the Touch Display 2 insists on operating in portrait mode when a device is attached to either HDMI port. After reading various posts, it would seem that the DSI output shares the framebuffer with HDMI when the latter is attached due to how it is implemented using KMS; the DSI output assumes whatever is sent to HDMI in text mode.
The video kernel parameter in cmdline.txt seemed to be a lost cause when HDMI is attached, so I looked for another option. I had discovered there is a rotation option to dtoverlay=vc4-kms--dsi-ili-9881-7inch, which gave me some hope—when operating as the sole display, all four rotation modes (0, 90, 180, 270) do indeed properly rotate the output on the Touch Display 2. What's frustrating is that when HDMI is attached, only rotation=0 and rotation=180 are respected, meaning the DSI mirroring will rotate... but only in portrait orientations.
I'm guessing this is probably another dead end that is by design and/or due to KMS restrictions, but I have to ask: should it be possible to force the Touch Display 2 to initiate in landscape mode with an HDMI display attached? It seems a bit short-sighted that one is constrained to portrait mode whenever a second display is attached, and I'm not sure why that would be the orientation to assumed to be the preferable default for a computer display when landscape has been the convention for decades.
Note that I do not need to worry about GUI support for the console. The only graphics I intend to display are via the RGBerry HAT, which I haven't even gotten to testing due to the DSI vs. HDMI orientation impediment. (I was willing to settle on a GUI that initiated mirrored displays at startup, but after numerous attempts to get Wayland et al to cooperate it seemed it also was asking too much for to create the desired configuration.)
After some searching it seems the only alternative to make this work would be to build a KMS-free Linux installation. Maybe an an older, non-KMS version of Debian/Raspberry Pi OS would work? In the end, this isn't going to be doing much more than running retro game emulation and connecting via SSH on an isolated LAN so I am not that concerned about keeping pace with the latest software.
Thanks in advance for any advice.
I have the following configuration:
* Raspberry Pi 4B
* 7" Touch Display 2
* SmartiPi Touch Pro 3 — case uses a landscape orientation
* HDMI-connected KVM
* CRT attached via RGBerry SCART HAT
* Debian 13 Trixie with updates applied
I am intending to use the 7" Touch Display 2 as a text console for running RetroPie on an external CRT via the RGBerry SCART HAT. Most of my hardware is on a KVM switch "network," and I'd like to mirror the Touch Display 2 at its 720 × 1280 native resolution as using a larger-than-7" display is often more desirable.
Unfortunately, no matter what settings I used in cmdline.txt and/or config.txt, the Touch Display 2 insists on operating in portrait mode when a device is attached to either HDMI port. After reading various posts, it would seem that the DSI output shares the framebuffer with HDMI when the latter is attached due to how it is implemented using KMS; the DSI output assumes whatever is sent to HDMI in text mode.
The video kernel parameter in cmdline.txt seemed to be a lost cause when HDMI is attached, so I looked for another option. I had discovered there is a rotation option to dtoverlay=vc4-kms--dsi-ili-9881-7inch, which gave me some hope—when operating as the sole display, all four rotation modes (0, 90, 180, 270) do indeed properly rotate the output on the Touch Display 2. What's frustrating is that when HDMI is attached, only rotation=0 and rotation=180 are respected, meaning the DSI mirroring will rotate... but only in portrait orientations.
I'm guessing this is probably another dead end that is by design and/or due to KMS restrictions, but I have to ask: should it be possible to force the Touch Display 2 to initiate in landscape mode with an HDMI display attached? It seems a bit short-sighted that one is constrained to portrait mode whenever a second display is attached, and I'm not sure why that would be the orientation to assumed to be the preferable default for a computer display when landscape has been the convention for decades.
Note that I do not need to worry about GUI support for the console. The only graphics I intend to display are via the RGBerry HAT, which I haven't even gotten to testing due to the DSI vs. HDMI orientation impediment. (I was willing to settle on a GUI that initiated mirrored displays at startup, but after numerous attempts to get Wayland et al to cooperate it seemed it also was asking too much for to create the desired configuration.)
After some searching it seems the only alternative to make this work would be to build a KMS-free Linux installation. Maybe an an older, non-KMS version of Debian/Raspberry Pi OS would work? In the end, this isn't going to be doing much more than running retro game emulation and connecting via SSH on an isolated LAN so I am not that concerned about keeping pace with the latest software.
Thanks in advance for any advice.
Statistics: Posted by grogdotnet — Mon Jan 12, 2026 5:11 pm — Replies 0 — Views 16