The Minor Number - Legacy vs. Persistent DSF

[gnaid]

Hi,

As we know,in legacy
DSFs, 15 bits in the minor number represent the device address, and 9 bits represent the
DSF’s special access options.
Persistent DSF minor numbers are also 24-bits. However, persistent DSFs use all 24 bits to
identify the device itself.
(As a result, persistent DSFs can represent 224 = 16,777,216 LUNs.)

I just wonder what happen with the access options?! Tape drives ussually have a suffix representing the compression,format, and other options enabled by the device file - tape0_BEST,tape0_BESTn, etc.

But,I don't think the name suffix is the only one left to represent access options ;)

[VK2COT]

Hello,

I hope I understand your question correctly.
Here is how HP-UX 11.31 defines DSFs for
tape drives and there is nothing more to it:

Best density, autorewind, AT&T style:
/dev/rtape/tape0_BEST

Best density, no autorewind, AT&T style:
/dev/rtape/tape0_BESTn

Best density, autorewind, Berkeley style:
/dev/rtape/tape0_BESTb

Best density, no autorewind, Berkeley style:
/dev/rtape/tape0_BESTnb

Cheers,

VK2COT

[gnaid]

Hello, VK2COT
thanks for the answer, but,no, I know that

I found something here:
HP-UX 11i v3 Mass Storage Device Naming
http://docs.hp.com/en/msDeviceNaming/Mass_Storage_Device_Naming.pdf

Introduction, page 3

About "The agile addressing scheme":
"It increases the scalability by using 24 bit opaque minor numbers and storing the device options separately. The binding between a minor number and certain device options is maintained in a system registry."

I don't have any idea what this SYSTEM REGISTRY is?


On the other hand, when I looked here "Driver Development Guide HP-UX 11i v3"( http://h21007.www2.hp.com/portal/download/files/unprot/ddk/DDR11iv3_new.pdf )

things seem to be a bit different :O
According to the Guide, the minor number information is still encoded in the device-special file(inode)?!


I/O Request Flow, page 37

"The following steps describe how a user request results in driver execution:
1. A user process makes an I/O system call and invokes the kernel through the system call
interface. The kernel manages the process and resources for the request.
2. The kernel gets the major and minor numbers.
If the file specified in the I/O system call is a device-special file, the kernel gets the major
and minor numbers from the file's inode. The kernel uses the major number to index into
a device switch table and sets up parameters, if any, to be passed to the driver.
....
"

and here:
Using Minor Numbers, page 35
"Minor numbers contain the location of the interface to which a device is attached and
driver-dependent characteristics. This information is organized by specific bit assignments. The
minor number information is encoded in the device-special file."