Re: mpt2sas and mpt3sas merge (again)

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On 07/14/2014 04:17 PM, James Bottomley wrote:
On Mon, 2014-07-14 at 11:22 +0200, Hannes Reinecke wrote:
On 07/14/2014 10:35 AM, Christoph Hellwig wrote:
Back when the mpt3sas driver was first posted I suggested that it should
be merged into mpt2sas, but my proposal didn't get much traction.

Illumos has now produced a shared driver and shown that the difference
are basically limited to a different S/G list format [1], and a quick
experiment on the Linux drivers confirms this mostly - the additional
differences are various smaller workarounds for specific hardware
revisions.

I think we'd all be served much better with a merged driver.

[1] http://thread.gmane.org/gmane.os.illumos.devel/17341

Please. Pretty please.

I support the concept, since I think everyone told LSI at the time that
splitting the drivers would become a maintenance nightmare.

I've started a merge myself, but then never found time to finalize it.

Carrying three basically identical drivers just creates a
maintenance overhead for everyone involved.

The original idea of splitting the driver and just maintaining the
latest has never really worked out; all fixes to the latest driver
turned out to be applicable to the others, too.
So it just increased the workload for the maintainer for no real
gain. I would _strongly_ vote for it.

This isn't really a democracy; it's about who maintains the drivers and
right now it's LSI (or whatever their new name is).

One of the big reasons we don't have a lot of leverage with them is that
they always seem to slide updates around upstream via the distros
(often,  it has to be admitted the DKM route), so if Red Hat, SUSE,
Oracle and Canonical can agree not to accept LSI updates until the
driver is done this way, we'd have a lot more leverage.

Hmm. We (as SUSE) have been striving to have a 'upstream first' policy. IE for any new release the drivers have to be upstream before we consider including it in our release. This is most certainly true for the upcoming SLE-12 release, and also has been enforced for the current SLES11 SP3 release.

This is official company policy, and has been communicated to all our partners. We do accept driver updates (ie patches which are not upstream ATM), but only on the understanding that the vendor will have to push the patches upstream eventually.
If they don't the patches will be kicked out of the next release.
(Which is what happened to the mptsas v4 release; it never made it upstream and so got dropped from SLE-12).

However, this cuts both ways; we cannot go and tell our partners to change the driver if upstream hasn't done it first.

So the push has to come from us (as the linux kernel developers); after all, we should make the decision what goes in and what doesn't. If a driver is in a bad state (and it's actually us which defines the 'bad state') we should be discussing on how we would like to improve things. If the maintainer proves unwilling to implement our suggestions we can always go ahead and implement a separate driver.

Look what happened to hpsa; this was the pretty much the showcase on how it should be done: Tomo went ahead and re-implemented the cciss driver, and eventually HP adopted it as their main driver.
I agree that was pretty much the optimal case, though:-)

Cheers,

Hannes
--
Dr. Hannes Reinecke		      zSeries & Storage
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SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg
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