In the struct fb_info structure, there is a .fbops field, which is an instance of the struct fb_ops structure. This structure contains a collection of functions that need to perform some operations on the framebuffer device. These are entry points for fbdev and fbcon tools. Some methods in that structure are mandatory, the minimum required for a framebuffer to work, whereas others are optional, and depend on the features the driver needs to expose, assuming the device itself supports those features.
The following is the definition of the struct fb_ops structure:
struct fb_ops {
/* open/release and usage marking */
struct module *owner;
int (*fb_open)(struct fb_info *info, int user);
int (*fb_release)(struct fb_info *info, int user);
/* For framebuffers with strange nonlinear layouts or that do not
* work with normal memory mapped...
