/dev/fb is mostly one thing: deprecated. Also it is not really a interface of your graphics card, it is a legacy way kindly still provided for pushing fullscreen pixels to your monitor in an unaccelerated fashion for things that have not made it to kms drm (which at this point is pretty much merely the console emulation on the TTYs). It is not an interface to the graphics card, because it doesn’t provide any capabilities a graphics card has (like shaders etc). In fact for just pushing pixels you can leave any graphics card completely out of your computer if you connect your screen by other means (think stuff like SPI which is common in embedded devices; you can find many examples of such drivers in the kernel source at drivers/gpu/drm/tiny ).
/dev/fb is mostly one thing: deprecated. Also it is not really a interface of your graphics card, it is a legacy way kindly still provided for pushing fullscreen pixels to your monitor in an unaccelerated fashion for things that have not made it to kms drm (which at this point is pretty much merely the console emulation on the TTYs). It is not an interface to the graphics card, because it doesn’t provide any capabilities a graphics card has (like shaders etc). In fact for just pushing pixels you can leave any graphics card completely out of your computer if you connect your screen by other means (think stuff like SPI which is common in embedded devices; you can find many examples of such drivers in the kernel source at drivers/gpu/drm/tiny ).