From: Grant Likely <grant.likely@linaro.org>
To: Jason Gunthorpe <jgunthorpe@obsidianresearch.com>,
Sylwester Nawrocki <s.nawrocki@samsung.com>
Cc: robh+dt@kernel.org, devicetree@vger.kernel.org,
linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH] of: Add of_device_destroy_children() function
Date: Wed, 14 May 2014 11:25:49 +0100 [thread overview]
Message-ID: <20140514102549.EEEF9C4153D@trevor.secretlab.ca> (raw)
In-Reply-To: <20140508203339.GA542@obsidianresearch.com>
On Thu, 8 May 2014 14:33:39 -0600, Jason Gunthorpe <jgunthorpe@obsidianresearch.com> wrote:
> On Thu, May 08, 2014 at 06:37:49PM +0200, Sylwester Nawrocki wrote:
> > This patch adds a helper function to unregister devices which
> > were created by an of_platform_populate() call. The pattern
> > used here can already be found in multiple drivers. This helper
> > can now be used instead of repeating similar code in drivers.
>
> I have a driver that does this as well, and what I found is that the
> remove must be in reverse order from the create or things explode, and
> that assumes the DT is topologically sorted according to dependency
> (so no deferred probe).
That is the tip of a much larger problem that we don't have any good way
to solve. There is no dependency tracking beyond the nature Linux driver
model tree. For example, the removal of a GPIO driver has no way to
tell users that it is going away, and so there is no way to force a
driver remove when it happens.
If we created a managed api for requesting resource (ie.
devm_request_gpio()), then it would be possible for the gpio core to
force a remove event on any driver that doesn't have the ability to
gracefully handle a remove.
The exact same problem exists for IRQs, clocks, regulators, or pretty
much any cross-tree dependency. :-(
> AFAIK, there is no analog to deferred probe for removal, and
> attempting to remove, say, a GPIO driver while an I2C bit bang is using
> it just fails.
Indeed, it is a completely different operation.
g.
next prev parent reply other threads:[~2014-05-14 10:25 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-05-08 16:37 [PATCH] of: Add of_device_destroy_children() function Sylwester Nawrocki
2014-05-08 20:33 ` Jason Gunthorpe
2014-05-09 9:53 ` Sylwester Nawrocki
2014-05-14 10:25 ` Grant Likely [this message]
2014-05-14 10:27 ` Grant Likely
2014-05-14 11:55 ` Sylwester Nawrocki
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