From mboxrd@z Thu Jan 1 00:00:00 1970 From: Pavel Machek Subject: Re: Runtime device power management in userspace Date: Tue, 27 Dec 2005 20:41:00 +0100 Message-ID: <20051227194100.GL1822@elf.ucw.cz> References: <20051223143047.GC16463@f192.suse.de> <20051224004029.GC16043@elf.ucw.cz> <20051226223325.GE1974@elf.ucw.cz> <20051227192254.GJ1822@elf.ucw.cz> <20051227192956.GA10704@digitalimplant.org> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable Return-path: Content-Disposition: inline In-Reply-To: <20051227192956.GA10704@digitalimplant.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: linux-pm-bounces@lists.osdl.org Errors-To: linux-pm-bounces@lists.osdl.org To: Patrick Mochel Cc: linux-pm@lists.osdl.org List-Id: linux-pm@vger.kernel.org On =DAt 27-12-05 11:29:56, Patrick Mochel wrote: > On Tue, Dec 27, 2005 at 08:22:54PM +0100, Pavel Machek wrote: >=20 > > I don't really think we want complexity of putting PCI device into > > D0/D1/D2/D3hot/D3cold. All that userspace should care about is device > > working/device suspended, and we could not test all 5 states, anyway. >=20 > What do you mean?=20 >=20 > The devices and drivers should support various states, and that's the > whole point of having multiple states - to make a choice based on the > power saving required vs. the latency requirements of bringing it back. >=20 > Granted, for most things, the latency to return from D3 (hot only, cold > is irrelevant during runtime) is not going to be noticable, so that's > probably the only state most devices will ever enter.=20 Exactly. And for these "most devices", having to test/debug/support D1/D2 is not worth the effort. > But, in some cases, peple are going to care about the intermediate > states, and we'll need to support them. It's simple enought to know > what states a PCI device supports, so I don't understand where the > complexity comes in.. ? Someone has to test all that... Unless we have in-tree driver that wants use intermediate states, I think supporting them is bad idea. Pavel --=20 Thanks, Sharp!