Re: [PATCH 2/3] Add EVPD page 0x83 to sysfs

Hannes Reinecke
2014-03-06T09:01:07Z

On 03/05/2014 08:42 PM, Christoph Hellwig wrote:
> On Wed, Mar 05, 2014 at 08:38:01AM +0100, Hannes Reinecke wrote:
>>> Either way I think the call to query evpd 0 should be a separate
>>> function, so even if we don't store the information it's abstracted out.
>>>
>> Hmm. That would work if we were just asking for a single page; but
>> when we're checking several pages (like 0x83 and 0x80) we'd need
>> either to pass in a page array or querying page 0 several times.
>> Neither of which is very appealing.
>>
>> However, specifying additional flags for the individual pages might
>> work. I'll see what I can come up with.
>
> Passing in a bitmask or flags seems useful. Even better storing it in the
> scsi_device. Note that I expect the place that need to know the EVPD
> patch to grow slowly but steadily over time.
>
I am somewhat reluctant here.

Adding separate flags like 'support_vpd_pg83' is a bit pointless,
given that we might as well check for vpg_pg83.

So the only 'proper' solution would be to add a bitmap of supported
pages; however, this would be 256 bits = 32 bytes of additional
space required for struct sdev.
Which I'm a bit reluctant do to, as it'll be a sparse array in most
cases, adding to quite some wasted space.

Thoughts?

Cheers,

Hannes
--
Dr. Hannes Reinecke zSeries & Storage
hare@suse.de +49 911 74053 688
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