On Mon, Sep 14, 2009 at 8:00 AM, Sosnowski, Maciej
[off-list ref] wrote:

Making the max_alloc_order a module parameter gives impression
that it can be modified by an user, including making it larger than default.
The default is however its maximum value, which may be confusing.
Why not to use parameter only as the upper limit?

It is the upper limit.

The user can limit the upper size of the descriptor ring by setting
this to a value less than 16.  By default it is the maximum ring size
that the driver/hardware* supports.  Specifying values greater than 16
are not supported by the so we need enforce a ceiling at 16.

--
Dan

* We could support ring sizes larger than 1 << 16 but we would need to
extra logic to ensure that the pending count never exceeded 1 << 16.
Simpler I think to just limit the maximum ring size.