HDMI Peripheral: Kernel Driver

This is a kernel module that drives the HDMI Peripheral for the Zynq 7000 defined by hdmi-cmd-gen and hdmi-cmd-enc. It exposes the peripheral as a framebuffer device, with additional ioctls for vertical syncing.

See also the hdmi-dev-video-player, which served as a precursor to this kernel module.

Building

This repository is a Yocto layer. It was tested with Petalinux 2023.2, which is based on Yocto Langdale, and uses Linux-Xilinx 6.1.30.

This layer exposes the ammrat13-hdmi-dev-mod package, which builds the kernel module and configures it to be loaded at boot via /etc/modules-load.d/.

Usage

This kernel module takes no command-line parameters, and only supports 640x480@60Hz since that's the only configuration supported by the hardware. Other than that, it exposes the HDMI Peripheral as a framebuffer device: /dev/fb*.

Additionally, this driver supports the ioctls for FBIOGET_VBLANK and FBIO_WAITFORVSYNC.

FBIOGET_VBLANK

This ioctl returns the current position of the scan dot, along with whether the screen is currently in: vertical blanking, horizontal blanking, and vertical sync. This never fails unless the address supplied as the first argument is invalid.

FBIO_WAITFORVSYNC

This ioctl waits until the scan dot is in vertical blanking. This does not necesarily wait for the next frame's vertical blanking interval. It returns 0 on success, or EINTR. It should never return ETIMEDOUT - something's gone wrong if it does.