On Tue, Oct 18, 2016 at 11:58 AM, Jeff Moyer <jmo...@redhat.com> wrote:
> Damien Le Moal <damien.lem...@wdc.com> writes:
>
>> +     if (!is_power_of_2(zone_blocks)) {
>> +             if (sdkp->first_scan)
>> +                     sd_printk(KERN_NOTICE, sdkp,
>> +                               "Devices with non power of 2 zone "
>> +                               "size are not supported\n");
>> +             return -ENODEV;
>> +     }
>
> Are power of 2 zone sizes required by the standard?  I see why you've
> done this, but I wonder if we're artificially limiting the
> implementation, and whether there will be valid devices on the market
> that simply won't work with Linux because of this.

The standard does not require power of 2 zones.
That said, I am not aware of any current (or planned) devices other
than a power of 2.
Common zone sizes I am aware of: 256MiB, 128MiB and 1GiB.

Also note that we are excluding the runt zone from the power of 2 expectation.

So conforming devices should (excluding a runt zone):
  - Have zones of the same size.
  - Choose a zone size that is a power of 2.

--Shaun

> -Jeff
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