Here is a list of all documented struct and union fields with links to the struct/union documentation for each field:

address : ssd1306_t
buffer : ssd1306_t
bufsize : ssd1306_t
external_vcc : ssd1306_t
height : ssd1306_t
i2c_i : ssd1306_t
pages : ssd1306_t
width : ssd1306_t