physio, minphys - perform physical I/O
int physio(int(*strat)(struct buf *), struct buf *bp, dev_t dev,
int rw, void (*mincnt)(struct buf *), struct uio *uio);
void minphys(struct buf *bp);
Solaris DDI specific (Solaris DDI).
Pointer to device strategy routine.
Pointer to a buf(9S) structure describing the transfer. If
bp is set to NULL then physio() allocates one which is auto‐
matically released upon completion.
The device number.
Read/write flag. This is either B_READ when reading from the
device, or B_WRITE when writing to the device.
Routine which bounds the maximum transfer unit size.
Pointer to the uio structure which describes the user I/O
Pointer to a buf structure.
DESCRIPTIONphysio() performs unbuffered I/O operations between the device dev and
the address space described in the uio structure.
Prior to the start of the transfer physio() verifies the requested
operation is valid by checking the protection of the address space
specified in the uio structure. It then locks the pages involved in the
I/O transfer so they can not be paged out. The device strategy routine,
strat(), is then called one or more times to perform the physical I/O
operations. physio() uses biowait(9F) to block until strat() has com‐
pleted each transfer. Upon completion, or detection of an error,
physio() unlocks the pages and returns the error status.
physio() uses mincnt() to bound the maximum transfer unit size to the
system, or device, maximum length. minphys() is the system mincnt()
routine for use with physio() operations. Drivers which do not provide
their own local mincnt() routines should call physio() with minphys().
minphys() limits the value of bp->b_bcount to a sensible default for
the capabilities of the system. Drivers that provide their own mincnt()
routine should also call minphys() to make sure they do not exceed the
RETURN VALUESphysio() returns:
CONTEXTphysio() can be called from user context only.
SEE ALSOstrategy(9E), biodone(9F), biowait(9F), buf(9S), uio(9S)
Writing Device Drivers
Since physio() calls biowait() to block until each buf transfer is com‐
plete, it is the drivers responsibility to call biodone(9F) when the
transfer is complete, or physio() will block forever.
Apr 2, 1993 PHYSIO(9F)