I am not sure if this will help with a lower-half of a NuttX driver, but this guy fooled around with bare metal programming on the RPi4 and had a graphics part of his dev experiments:
https://www.rpi4os.com/ <https://www.rpi4os.com/> His code is on GitHub and is under a CC license. I have not looked at it, but it might be worth a gander. https://github.com/babbleberry/rpi4-osdev Cheers, Ian > On Nov 5, 2025, at 3:48 PM, Matteo Golin <[email protected]> wrote: > > Hi all, > > Despite a relatively small bug with transfer size limits, the RPi4B microSD > card support is basically done. This is largely in part to how simple it is > on NuttX to write a lower-half SDIO implementation and have things just > work, which is incredible :) > > I now (ambitiously) want to set my eyes on graphics. It turns out that > rendering with a framebuffer is actually quite easy, but very CPU > intensive. I'm going to need to figure out how to get at the GPU properly. *My > question is: *is anyone familiar with examples on how to implement the > necessary "lower-half" for the NuttX graphics library? I.e. what > functions/drivers I would need to get written to allow the basic windowing > display manager & LVGL to work on the HDMI outputs of the Pi? I have > briefly read the docs about the window manager and saw that there is a > framebuffer char driver that can be implemented, but I'm not sure how well > that scales to decent graphics. I suppose this is relatively uncharted > territory on an RTOS designed mainly with LCDs in mind as the only graphics > (?). If anyone has implemented graphics support for a device before and can > let me know a few source files to look at, that would be great! > > My main goal is essentially to get decently fast graphics going, since once > that's done and some USB HID device support is set up, I can port DOOM to > NuttX :) > > Thanks, > Matteo >
