RE: Request for comments (kdev_t and friends...)

Bret Indrelee (bindrelee@sbs-cp.com)
Sat, 27 Nov 1999 15:33:53 -0600

Linus Torvalds wrote:
> > Further, major and minor don't make much sense either anymore. Major
> > should indicate a device type, with minor indicating an
> instance. But now
> > there are multiple devices within a major (misc, mem) and
> devices that
> > span majors (tty, scsi). So the terms are more or less
> arbitrary. So most
> > of the kernel outside drivers themselves should treat
> device handles as
> > opaque.
>
> The major/minor stuff should never be used in a perfect
> world, except for
> the initial lookup. After that, you would just have "index within this
> controller" or something, and that depends on the actual hardware.

What about drivers that use the minor number to indicate instance number or
special modes of operation?

The major number is just something that the system uses to convert from the
user concept of 'open the device at this inode' into a table lookup. Device
drivers shouldn't care about their major number.

The minor number for some devices has been and continues to indicate
operating mode for certain devices.

-Bret

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Bret Indrelee, Engineer
SBS Technologies, Inc., Connectivity Products
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