SVR5

physiock(D3)

physiock -- validate and issue a raw I/O request

Synopsis (Not in current DDI version)

   #include <sys/types.h>
   #include <sys/buf.h>
   #include <sys/uio.h>
   #include <sys/ddi.h>
   
   int physiock(void (*strat)(), buf_t *bp,
                dev_t dev, int rwflag,
   	     daddr_t nblocks, uio_t *uiop);

Description

physiock( ) is called by the character (raw) interface ioctl(D2), read(D2), and write(D2) routines of block drivers to help perform unbuffered I/O while maintaining the buffer header as the interface structure.

Arguments

strat: Address of the driver strategy(D2) routine, or similar function.
bp: Pointer to the buf(D4) structure describing the I/O request.
dev: External device number.
rwflag: Flag indicating whether the access is a read or a write.
nblocks: Number of blocks that the logical device dev can support.
uiop: Pointer to the uio(D4) structure that defines the user space of the I/O request.

Return values

physiock( ) returns 0 if the result is successful, or the appropriate error number on failure. If a partial transfer occurs, the uio structure is updated to indicate the amount not transferred and an error is returned:

ENXIO: an attempt was made to read beyond the end of the device or an attempt was made to write at or beyond the end of a the device.
EFAULT: User memory is not valid.
EAGAIN: physiock( ) could not lock all of the pages.

If a read is performed at the end of the device, 0 is returned.

Usage

physiock( ) performs the following functions:

Verifies the requested transfer is valid by checking if the offset is at or past the end of the device. This check is bypassed if the size parameter argument nblocks is zero.
Sets up a buffer header describing the transfer.
Faults pages in and locks the pages impacted by the I/O transfer so they can't be swapped out.
Calls the driver strategy( ) routine passed by the (strat) argument.
Blocks until the transfer is complete and is awakened by a call to biodone(D3) from the driver's I/O completion handler.
Performs the necessary cleanup and updates, then returns to the calling routine.

A transfer using physiock( ) is considered valid if the specified data location exists on the device, and the user has specified a storage area large enough that exists in user memory space.

If bp is set to NULL, a buffer is allocated temporarily and freed after the transfer completes.

If rwflag is set to B_READ, the direction of the data transfer will be from the kernel to the user's buffer. If rwflag is set to B_WRITE, the direction of the data transfer will be from the user's buffer to the kernel.

One block is equal to NBPSCTR bytes. NBPSCTR is defined in sys/param.h.

Some device drivers need nblocks to be arbitrarily large (for example, for tapes whose sizes are unknown). In this case, nblocks should be no larger than (2[22])-1. For arbitrarily large cases on SVR4.2 MP systems, nblocks should be 0 (zero).

Context and synchronization

User context.

Examples

See dma_pageio(D3) for an example of physiock.

Hardware applicability

All

Version applicability

ddi: 1, 2, 3, 4, 5, 5mp, 6, 6mp, 7, 7mp, 7.1, 7.1mp

Differences between version

physiock(D3) is not supported in DDI 8; use do_biostart(D3) instead.

SCO OpenServer ODDI compatibility

SCO OpenServer ODDI drivers use the physio(D3oddi) and physck(D3oddi) functions rather than physiock( ).

References

buf(D4), dma_pageio(D3), ioctl(D2), read(D2), strategy(D2), uio(D4), write(D2)