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gensio_set_read_callback_enable(3) Library Functions Manual gensio_set_read_callback_enable(3)

NAME

gensio_set_read_callback_enable, gensio_set_write_callback_enable - Enable or disable read data and write ready

SYNOPSIS

#include <gensio/gensio.h>
void gensio_set_read_callback_enable(struct gensio *io,

bool enabled);
void gensio_set_write_callback_enable(struct gensio *io,

bool enabled);

DESCRIPTION

These function enable the write callback, or the read callback, for gensios (and all child gensios). Generally disabling the read callback will disable all callbacks except write because it won't receive any data to do any processing.

After you open a gensio or receive a gensio from an accepter, the gensio has all the enables set to false. You would generally want to enable the read callback and leave it enabled as much as possible so that low-level processing will happen on the gensio. In particular, disabling read on a UDP gensio will disable all read an accept processing.

Enabling the write callback will enable the callback to tell you if the gensio can currently write any data. You normally want to leave this disabled and enable it if you write data and get a partial write. Or even better, when you have data to write, enable the write callback and write the data from the callback, disabling when it is all written.

Disabling the write callback does not necessarily keep data from being transmitted by the gensio. The SSL gensio, for instance, may transmit key information on a rekey, or other gensios may transmit flow-control information. This only affects the write callback.

Disabling the callbacks may not be immediate. "Immediate" is hard to define in a SMP system, anyway. There may be callbacks running or about to be called when you disable the callback, they may still run. You must be prepared to handle these race conditions.

RETURN VALUES

Zero is returned on success, or a gensio error on failure.

SEE ALSO

gensio_err(3), gensio(5)
27 Feb 2019