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.Dd September 8, 2008 .Dt DEVFS_CDEVPRIV 9 .Os .Sh NAME .Nm devfs_set_cdevpriv , .Nm devfs_get_cdevpriv , .Nm devfs_clear_cdevpriv .Nd manage per-open filedescriptor data for devices .Sh SYNOPSIS n sys/param.h n sys/conf.h d -literal typedef void (*cdevpriv_dtr_t)(void *data); .Ed .Ft int .Fn devfs_get_cdevpriv "void **datap" .Ft int .Fn devfs_set_cdevpriv "void *priv" "cdevpriv_dtr_t dtr" .Ft void .Fn devfs_clear_cdevpriv "void" .Sh DESCRIPTION The .Fn devfs_xxx_cdevpriv family of functions allows the .Fa cdev driver methods to associate some driver-specific data with each user process .Xr open 2 of the device special file. Currently, functioning of these functions is restricted to the context of the .Fa cdevsw switch method calls performed as .Xr devfs 5 operations in response to system calls that use filedescriptors.
p The .Fn devfs_set_cdevpriv function associates a data pointed by .Va priv with current calling context (filedescriptor). The data may be retrieved later, possibly from another call performed on this filedescriptor, by the .Fn devfs_get_cdevpriv function. The .Fn devfs_clear_cdevpriv disassociates previously attached data from context. Immediately after .Fn devfs_clear_cdevpriv finished operating, the .Va dtr callback is called, with private data supplied .Va data argument.
p On the last filedescriptor close, system automatically arranges .Fn devfs_clear_cdevpriv call.
p If successful, the functions return 0.
p The function .Fn devfs_set_cdevpriv returns the following values on error: l -tag -width Er t Bq Er ENOENT The current call is not associated with some filedescriptor. t Bq Er EBUSY The private driver data is already associated with current filedescriptor. .El
p The function .Fn devfs_get_cdevpriv returns the following values on error: l -tag -width Er t Bq Er EBADF The current call is not associated with some filedescriptor. t Bq Er ENOENT The private driver data was not associated with current filedescriptor, or .Fn devfs_clear_cdevpriv was called. .El .Sh SEE ALSO .Xr open 2 , .Xr close 2 , .Xr devfs 5 , .Xr kern_openat 9 .Sh HISTORY The .Fn devfs_cdevpriv family of functions first appeared in .Fx 7.1 .