scsi_alloc(D3X)scsi_alloc(D3X)NAMEscsi_alloc - allocate communication channel to host adapter driver
SYNOPSIS
#include <sys/types.h>
#include <sys/scsi.h>
int
(*scsi_alloc)( vertex_hdl_t lun_vhdl,
int option,
void (*callback_function)(vertex_hdl_t, char *));
DESCRIPTION
A kernel level SCSI device driver calls the host adapter scsi_alloc
function to initialize a communication connection between itself and a
host adapter driver, in preparation for issuing SCSI commands.
There is no kernel object called scsi_alloc; rather, there is a pointer
to each host adapter's scsi_alloc function in the sci_alloc field of the
scsi_ctlr_info structure, which is attached to the vertex corresponding
to the host adapter.
The lun_vhdl argument specifies the hwgraph vertex for the device. The
option argument currently has two fields:
o SCSIALLOC_EXCLUSIVE indicates that the driver needs exclusive use
with the device.
o SCSIALLOC_QDEPTH is an 8-bit mask specifying the maximum number of
commands that the device driver will want to queue. It is advisory
only and may be ignored by the host adapter driver.
The callback_function may be useful for drivers that don't use the
SCSIALLOC_EXCLUSIVE option. When callback_function is NULL, it is
ignored. When non-NULL, it specifies a function to call whenever there
is sense data from device. It can be useful when more than one device
driver will talk to a SCSI device, but one of the drivers needs to know
about things like media removals. Only one device driver may specify a
callback_function for a given device. The callback function is called
with two arguments, the vertex handle corresponding to the SCSI lun and
the sense data. The vertex handle allows a driver to know which device
the callback pertains to.
DIAGNOSTICSscsi_alloc returns 0 if a communication connection could not be
established, or if the arguments are invalid, or if the device was
already allocated in exclusive use mode, or if this request was for
exclusive use and the device is already allocated (including possibly
earlier requests by the same driver). Otherwise, it returns a positive
value.
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scsi_alloc(D3X)scsi_alloc(D3X)NOTESscsi_alloc is stored as a function pointer in the scsi_ctlr_info_t
structure, which is associated with the scsi host adapter vertex in the
hwgraph. The information structure in the scsi target vertex also has a
pointer to the scsi_ctlr_info_t of the host adapter that the target is
connected to. Given a lun_vhdl (vertex handle of the device) the
scsi_alloc function can be called as follows:
scsi_lun_info_t *scsi_lun_info;
...
scsi_lun_info = scsi_lun_info_get(lun_vhdl);
SLI_ALLOC(scsi_lun_info)(lun_vhdl,option,callback_function);
SEE ALSO
comments in /usr/include/sys/scsi.h, hwgraph.intro(D4X), scsi_free(D3X),
scsi_info(D3X), scsi_command(D3X), scsi_ioctl(D3X), scsi_abort(D3X), SCSI
chapter of the IRIX Device Driver Programmer's Guide.
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