DKI Changes

• Device numbers are passed as a dev_t rather than as an int in prior IRIX versions. As mentioned elsewhere, the DDI contains new functions to access the major and minor numbers. Note that open takes a dev_t *, while read and write take a dev_t (no indirection).

• Many of the entry points (open, close, read, write) take a new argument that is an opaque credentials structure. (It is opaque in the sense that the device driver never examines the internal makeup of the structure.) This is used to call the DDI drv_priv() routine, which takes the place of checking u.u_uid == 0. This permits different models of privileges to be used, for example, in a trusted system.

• The read and write routines take a uio_t *, a pointer to a structure that defines the addresses and lengths of the data in the user space. (The IRIX Device Driver Reference Pages describe this structure. It is defined in /usr/include/sys/uio.h.) Previously, this information was computed in the driver from the u vector. The driver typically passes this structure to a DMA setup routine such as the DDI uiophysio() or the Silicon Graphics enhancement, biophysio(), which is nearly identical to iophysio(), except that it takes a block number instead of a file offset).

• Generally, drivers can no longer access the u vector directly. DDI defines access routines for fields in the u vector. Direct access to the u vector tends to make a driver more dependent on specific aspects of the system than is desirable. This also extends to access u.u_error. DKI expect to return the error value (0 indicates no error), and are not supposed to set u.u_error.

• Interrupt routines are now of type void.

Addressability