Generally speaking...

Generally speaking, returning directory entries is just like returning raw data, with the exceptions listed here.

• You must return an integral number of struct dirent entries.
• You must fill in the struct dirent entries.

The first point means that you cannot return, for example, seven and a half struct dirent entries. If eight of these structures don't fit into the allotted space, then you must return only seven.

The second point is fairly obvious; it's mentioned here only because filling in the struct dirent can be a little tricky compared to the raw data approach for a normal read I/O function handler.