It all depends on exactly which camera and which lens you are considering.

In most cases when you use a modern digital camera and lens that are both made by the same manufacturer the lens reports this information to the camera, along with other identifying information that tells the camera things such as the specific model of the lens, the current focal length for a zoom lens, and sometimes even the lens' serial number. In the case of your Canon EOS camera, any Canon EF or EF-S lens will report that and more to the camera body. Most modern third party lenses also are "chipped" to speak the language of the camera brand upon which they are designed to mount.

Although not the case with the Canon EOS system, some older lenses that will still mount on a much newer camera from the same manufacturer do not communicate with the camera body and the aperture range the lens is capable of is not indicated by the camera. In some situations, the camera uses mechanical linkage to stop down the lens. In other cases the aperture is set on the lens itself and the camera may or may not be able to detect the aperture setting. If the camera can not detect the setting, then shooting must be done in Manual exposure mode. Sometimes metering can be accomplished with the lens stopped down, sometimes the result of metering must be manually adjusted to compensate for the difference between metering when the aperture is wide open and the aperture used when the diaphragm is stopped down and the shutter is open.