SOCU:poll

Request

Index Word	Description
0	Header code [0x00140084]
1	nfds_t nfds
2	int timeout
3	Value 0x20 (processID header)
4	ProcessID set by the ARM11 kernel.
5	(insize<<14) | 0x2802
6	Pointer to input pollfd struct array

The following is located 0x100-bytes after the beginning of the above command buffer:

Index Word	Description
0	(outsize<<14) | 2
1	Pointer to output pollfd struct array

Response

Index Word	Description
0	Header code
1	Result code
2	POSIX return value

pollfd struct

Type	Name	Description
u32	fd	Socket handle
u32	events	Events to poll for (input)
u32	revents	Events received (output)

Events

Events are a bitwise set of these flags. These flags don't exactly match the Wii flags, even though the sockets sysmodule uses the same codebase.

Value	Name	Description
0x01	POLLIN	Data can be read.
0x02	POLLPRI	Urgent data can be read.
0x08	POLLWRNORM	Normal data can be written.
0x10	POLLWRBAND	Priority data can be written.
0x20	POLLNVAL	Invalid socket handle.
POLLWRNORM	POLLOUT	Data can be written.

Flag 0x4 isn't ever assigned in the code. Flags 0x40 and 0x80 are also not used, even though they are assgined in the input events by default along with 0x20. This is likely because that code section was inherited from the Wii, where these flags are used for poll errors.

Contrary to the Wii sockets, the 3DS doesn't have POLLERR or POLLHUP, so poll shouldn't be relied on when checking for socket errors.