SIZE(9P) Kernel Properties for Drivers SIZE(9P)


NAME


size, Nblock, blksize, device-nblocks, device-blksize - device size
properties

DESCRIPTION


A driver can communicate size information to the system by the values
associated with following properties. Size information falls into two
categories: device size associated with a dev_info_t node, and minor node
size associated with a ddi_create_minor_node(9F) dev_t (partition).


device size property names:

device-nblocks
An int64_t property representing device size in device-
blksizeblocks.


device-blksize
An integer property representing the size in bytes of a
block. If defined, the value must be a power of two. If
not defined, DEV_BSIZE is implied.


minor size property names:

Size
An int64_t property representing the size in bytes of a
character minor device (S_IFCHR spec_type in
ddi_create_minor_node).


Nblocks
An int64_t property representing the number blocks, in device-
blksize units, of a block minor device (S_IFBLK spec_type in
ddi_create_minor_node).


blksize
An integer property representing the size in bytes of a block.
If defined, the value must be a power of two. If not defined,
DEV_BSIZE is implied.


A driver that implements both block and character minor device nodes
should support both "Size" and "Nblocks". Typically, the following is
true: Size = Nblocks * blksize.


A driver where all ddi_create_minor_node(9F) calls for a given instance
are associated with the same physical block device should implement
"device-nblocks". If the device has a fixed block size with a value other
than DEV_BSIZE then "device-blksize" should be implemented.


The driver is responsible for ensuring that property values are updated
when device, media, or partition sizes change. For each represented item,
if its size is know to be zero, the property value should be zero. If its
size is unknown, the property should not be defined.


A driver may choose to implement size properties within its prop_op(9E)
implementation. This reduces system memory since no space is used to
store the properties.


The DDI property interfaces deal in signed numbers. All Size(9P) values
should be considered unsigned. It is the responsibility of the code
dealing with the property value to ensure that an unsigned interpretation
occurs.

ATTRIBUTES


See attributes(5) for descriptions of the following attributes:


+--------------------+-----------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+--------------------+-----------------+
|Interface Stability | Committed |
+--------------------+-----------------+

SEE ALSO


attach(9E), detach(9E), prop_op(9E), ddi_create_minor_node(9F), inquiry-
vendor-id(9P)


Writing Device Drivers


January 23, 2008 SIZE(9P)