write(D2)

NAME
     write - write data to a device

SYNOPSIS
     #include <sys/types.h>
     #include <sys/errno.h>
     #include <sys/uio.h>
     #include <sys/cred.h>
     #include <sys/ddi.h>
     int prefixwrite(dev_t dev, uio_t *uiop, cred_t *crp);

   Arguments
     dev       Device number.

     uiop      Pointer to the uio(D4) structure that describes where the data
               is to be fetched from user space.

     crp       Pointer to the user credential structure for the I/O
               transaction.

DESCRIPTION
     The driver write routine is called during the write(2) system call.  The
     write routine is responsible for transferring data from the user data
     area to the device.

   Return Values
     The write routine should return 0 for success, or the appropriate error
     number.

USAGE
     This entry point is optional, and is valid for character device drivers
     only.

     The pointer to the user credentials, crp, is available so the driver can
     check to see if the user can write privileged information, if the driver
     provides access to any.  The uio structure provides the information
     necessary to determine how much data should be transferred.  The
     uiomove(D3) function provides a convenient way to copy data using the uio
     structure.

     Block drivers that provide a character interface can use physiock(D3) to
     perform the data transfer with the driver's strategy(D2) routine.

   Synchronization Constraints
     The write routine has user context and can sleep.

     The write operation is intended to be synchronous from the caller's
     perspective.  Minimally, the driver write routine should not return until
     the caller's buffer is no longer needed.  For drivers that care about
     returning errors, the data should be committed to the device.  For
     others, the data might only be copied to local staging buffers.  Then the
     data will be committed to the device asynchronously to the user's
     request, losing the ability to return an error with the associated
     request.

REFERENCES
     drv_priv(D3), errnos(D5), physiock(D3), read(D2), strategy(D2), uio(D4),
     uiomove(D3), uwritec(D3)