This function should write a unique id into id and return GP_OK. That is,
choose a unique id, use strncpy in order to copy it into the id, and
return GP_OK.
This function should use gp_abilities_list_append as many times as the
number of models the camera driver supports. That is, fill out (in a loop)
the CameraAbilities for each model and append each of those to the
supplied list using gp_abilities_list_append. Then, return GP_OK.
int camera_init (Camera *camera,
GPContext *context);
This is the most interesting function in your library. Here, you tell
gphoto2 what operations your camera supports and you try to connect
to the camera. That is, access camera->functions directly and set them
to your implementation (if you have any). Then, tell the CameraFilesystem
(available in camera->fs) how to retrieve lists
(gp_filesystem_set_list_funcs), how to retrieve or set file information
(gp_filesystem_set_info_funcs), how to get or delete files
(gp_filesystem_set_file_funcs), or how to put files or delete all files
in a folder (gp_filesystem_set_folder_funcs). After that, configure
the port (camera->port) which is already opened by gphoto2. You just have
to call gp_port_settings_get, adjust the settings, call
gp_port_settings_set, and try to write to and read from the port.
If the camera responds, return GP_OK. If not, return some
meaningful error code.
