> My understanding of the memory access provided by fbdev is that it's an extremely simple API.
Maybe some of fbdev are like that, but most of them are not. They use vga/vesa interfaces to get a real video memory and write into it. A text console is also using vga video memory to write character data into it.
I still wonder do there any ways to use VGA at its full. Like loading sprites into invisible on the screen video memory and copying them into their right place on the screen. VGA allowed to copy 8 of 4-bit pixels by copying one byte, for example. Were these things just dropped off for a nice abstraction, or maybe there is some ioctls to switch modes for read/writes into video memory? I don't know and never was interested enough to do a research.
> In other words an outdated abstraction that's still useful so it's kept around.
Yes, it is kinda like this, but the outdated abstraction is realized on video card, kernel just gives access to it.
In Linux fbdev is more like a fallback device when drivers for a specific video card are not accessible. fbdevs are used to make a text console with more than 80x25 characters. Video acceleration or opengl can work on fbdev only as a software implementation.
Most GPU drivers these days are DRM drivers, which implement fbdev support for backwards compatibility only [0]. The fbdev API is primarily "fake" these days.
DRM/KMS using dumb buffers are the preferred API if you want to do software rendering and modesetting. You can find several examples of this online if you search for drm_mode_create_dumb.
Maybe some of fbdev are like that, but most of them are not. They use vga/vesa interfaces to get a real video memory and write into it. A text console is also using vga video memory to write character data into it.
I still wonder do there any ways to use VGA at its full. Like loading sprites into invisible on the screen video memory and copying them into their right place on the screen. VGA allowed to copy 8 of 4-bit pixels by copying one byte, for example. Were these things just dropped off for a nice abstraction, or maybe there is some ioctls to switch modes for read/writes into video memory? I don't know and never was interested enough to do a research.
> In other words an outdated abstraction that's still useful so it's kept around.
Yes, it is kinda like this, but the outdated abstraction is realized on video card, kernel just gives access to it.
In Linux fbdev is more like a fallback device when drivers for a specific video card are not accessible. fbdevs are used to make a text console with more than 80x25 characters. Video acceleration or opengl can work on fbdev only as a software implementation.