Flush Handling

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All modules and drivers are expected to handle the flushing of messages. The user may cause data to be flushed of queued messages from a stream by the submission of an I_FLUSH ioctl(2). Data may be flushed from the read side, write side, or both sides of a stream.

ioctl (fd, I_FLUSH, arg);

Table 4–4 describes the arguments that may be passed to M_FLUSH.

Table 4-4 M_FLUSH Arguments and bi_flag values

Flag	Description
`FLUSHR`	Flushes read side of stream
`FLUSHW`	Flushes write queue
`FLUSHRW`	Flushes both read and write queues

In addition to being able to flush all the data from a queue, a specific band may be flushed using the I_FLUSHBAND ioctl(2).

ioctl (fd, I_FLUSHBAND, bandp);

The ioctl(2) is passed a pointer to a bandinfo structure. The bi_pri field indicates the band priority to be flushed (values from 0 to 255). The bi_flag field indicates the type of flush to do. The legal values for bi_flag are defined in Table 4–4. bandinfo has the following format:

struct bandinfo {
		unsigned char    bi_pri;
		int              bi_flag;
};

See Flushing Priority Band, which describes M_FLUSHBAND processing, for details on how modules and drivers should handle flush band requests.