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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.
See attributes(5) for descriptions of the following attributes:
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
| Interface Stability | Committed |
attach(9E), detach(9E), prop_op(9E), ddi_create_minor_node(9F), inquiry-vendor-id(9P)
Writing Device Drivers