linux-kernel - Re: removing existing working drivers via staging

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Date:	Thu, 15 Oct 2009 12:38:09 -0700 (PDT)
From:	david@...g.hm
To:	Ingo Molnar <mingo@...e.hu>
cc:	Greg KH <gregkh@...e.de>,
	Bartlomiej Zolnierkiewicz <bzolnier@...il.com>,
	Stefan Richter <stefanr@...6.in-berlin.de>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: removing existing working drivers via staging

On Thu, 15 Oct 2009, Ingo Molnar wrote:

> * david@...g.hm <david@...g.hm> wrote:
>
>>> But a driver in staging still has to be able to build, api changes
>>> are not able to be ignored in it.
>>
>> a driver in staging will be able to build, but a driver that was
>> removed after 6-9 months that a user discovered the removal of a year
>> later when they upgraded to a new distro release (say a normal ubuntu
>> release after staying on the old one for the 18 month support period)
>> is likely to need significant work to catch up with kernel changes in
>> the meanwhile.
>
> Where do you get the 6-9 months from? Greg said he'll wait 3 kernel
> releases. Here's the timeline of that:

that was the timeframe listed in the prior discussion, 3 kernel releases * 
2-3 months/release works out to this

> - release x
> - [A] driver moves into drivers/staging/ in the staging tree
> - release x+1
> - drivers/staging/ change gets merged in the x+2 merge window
> - release x+2 - first kernel with the driver in staging
> - release x+3
> - release x+4
> - driver gets removed in the staging tree
> - release x+5 - 3 kernel releases passed - now it's removed
> - removal propagates upstream in the x+6 merge window
> - [B] release x+6

I would have seen this as

release x
driver moves into staging
release x+1
release x+2
release x+3
driver is removed
release x+4 no longer has the driver

> from the decision to move it into staging there's 4 kernel releases
> during which the information is known, and 3 full kernel releases with
> the driver is actually moved, and even in the 4th cycle there's still 3
> months to undo the removal if there's objections (i.e. it's a
> regression).
>
> This means the timeline is 4*3 = 12 months _at minimum_. In practice it
> will be more than a year - up to 1.5 years. Well within most distros ~3
> months upstream kernel update schedule.

yes, this is well past the distro update cycle for new releases, but not 
within the user update cycle. there are a LOT of people who don't upgrade 
every 6 months. every distro provides support for at least 12 months, if 
not more. and even then there are a lot of people who drop out of their 
distro support before they upgrade.

it's these users who will discover the missing driver and care about it, 
not the distros.

personally, I try to do a kernel update every year (if security concerns 
in a feature that I have compiled in don't force me to upgrade sooner) 
sometimes with a distro upgrade, sometimes not.

David Lang
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