From: Matthew Garrett <mjg59@srcf.ucam.org>
To: Tejun Heo <tj@kernel.org>
Cc: Lin Ming <ming.m.lin@intel.com>, Jeff Garzik <jgarzik@pobox.com>,
Alan Stern <stern@rowland.harvard.edu>,
linux-kernel@vger.kernel.org, linux-ide@vger.kernel.org,
linux-pm@vger.kernel.org, "Rafael J. Wysocki" <rjw@sisk.pl>,
kay.sievers@vrfy.org
Subject: Re: [RFC][PATCH 4/4] ahci: support hot plug when port/controller is runtime suspended
Date: Mon, 2 Jan 2012 15:57:11 +0000 [thread overview]
Message-ID: <20120102155711.GA10202@srcf.ucam.org> (raw)
In-Reply-To: <20111215192131.GE32002@google.com>
On Thu, Dec 15, 2011 at 11:21:31AM -0800, Tejun Heo wrote:
> SATA link detection requires hot wire and keeping wire hot takes
> power. I think it's fair tradeoff to not support hotplug while
> powersaving is on. We have warm plug mechanism (the SCSI rescan
> trigger via sysfs) after all. It would be nice if things like that is
> somehow exported to userland in easy way tho (cc'ing Kay), but I
> frankly don't have much idea where that would fit.
We expose the ahci_port_cmd field in sysfs, which lets us know whether a
port is flagged as hotpluggable or external. Userspace could use that to
identify whether a given port can be safely powered off or not. It's not
guaranteed - desktop boards with esata ports will typically not have
this information available (because the esata port could be plugged into
any on-board port), so I think leaving it up to userspace to set the
policy makes sense.
--
Matthew Garrett | mjg59@srcf.ucam.org
prev parent reply other threads:[~2012-01-02 15:57 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-12-15 13:12 [RFC][PATCH 0/4] ahci controller runtime PM support Lin Ming
2011-12-15 13:12 ` [RFC][PATCH 1/4] ahci: port legacy pm interface to struct dev_pm_ops Lin Ming
2011-12-15 19:53 ` Rafael J. Wysocki
2011-12-16 13:07 ` Lin Ming
2011-12-15 13:12 ` [RFC][PATCH 2/4] ahci: add runtime PM callbacks Lin Ming
2011-12-15 13:12 ` [RFC][PATCH 3/4] ata: runtime suspend port if no device attached Lin Ming
2011-12-15 13:12 ` [RFC][PATCH 4/4] ahci: support hot plug when port/controller is runtime suspended Lin Ming
2011-12-15 19:21 ` Tejun Heo
2011-12-15 23:29 ` Kay Sievers
2012-01-02 15:57 ` Matthew Garrett [this message]
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