From mboxrd@z Thu Jan 1 00:00:00 1970 From: Russell King Date: Thu, 29 Apr 2004 21:42:43 +0000 Subject: Re: [PATCH] Hotplug for device power state changes Message-Id: <20040429224243.L16407@flint.arm.linux.org.uk> List-Id: References: <20040429202654.GA9971@dhcp193.mvista.com> In-Reply-To: <20040429202654.GA9971@dhcp193.mvista.com>; from tpoynor@mvista.com on Thu, Apr 29, 2004 at 01:26:54PM -0700 MIME-Version: 1.0 Content-Type: text/plain; charset="macroman" Content-Transfer-Encoding: base64 To: Todd Poynor Cc: mochel@digitalimplant.org, linux-hotplug-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org T24gVGh1LCBBcHIgMjksIDIwMDQgYXQgMDE6MjY6NTRQTSAtMDcwMCwgVG9kZCBQb3lub3Igd3Jv dGU6Cj4gQSBwYXRjaCB0byBjYWxsIGEgaG90cGx1ZyBkZXZpY2UtcG93ZXIgYWdlbnQgd2hlbiB0 aGUgcG93ZXIgc3RhdGUgb2YgYQo+IGRldmljZSBpcyBtb2RpZmllZCBhdCBydW50aW1lICh0aGF0 IGlzLCBpbmRpdmlkdWFsbHkgdmlhIHN5c2ZzIG9yIGJ5IGEKPiBkcml2ZXIgY2FsbCwgbm90IGFz IHBhcnQgb2YgYSBzeXN0ZW0gc3VzcGVuZC9yZXN1bWUpLiAgQWxsb3dzIGEgcG93ZXIKPiBtYW5h Z2VtZW50IGFwcGxpY2F0aW9uIHRvIGJlIGluZm9ybWVkIG9mIGNoYW5nZXMgaW4gZGV2aWNlIHBv d2VyIG5lZWRzLgo+IFRoaXMgY2FuIGJlIHVzZWZ1bCBvbiBwbGF0Zm9ybXMgd2l0aCBkZXBlbmRl bmNpZXMgYmV0d2VlbiBzeXN0ZW0KPiBjbG9jay92b2x0YWdlIHNldHRpbmdzIGFuZCBvcGVyYXRp b24gb2YgY2VydGFpbiBkZXZpY2VzIChzdWNoIGFzCj4gUFhBMjd4KSwgb3IsIGZvciBleGFtcGxl LCBvbiBhIGNlbGwgcGhvbmUgd2hlcmUgdm9pY2ViYW5kIG9yIG5ldHdvcmsKPiBkZXZpY2VzIGdv aW5nIGluYWN0aXZlIHNpZ25hbHMgYW4gb3Bwb3J0dW5pdHkgdG8gbG93ZXIgcGxhdGZvcm0gcG93 ZXIKPiBsZXZlbHMgdG8gY29uc2VydmUgYmF0dGVyeSBsaWZlLgoKTm90ZSB0aGF0IHdlIHNob3Vs ZCBydW4gdGhpcyBzeW5jaHJvbm91c2x5IHdpdGggdXNlcnNwYWNlIC0gaWUsIHdhaXQKZm9yIHRo ZSB1c2Vyc3BhY2UgaG90cGx1ZyBzY3JpcHQgdG8gZmluaXNoIGV4ZWN1dGluZyBiZWZvcmUgbW92 aW5nCm9uIHRvIHRoZSBuZXh0IGRldmljZS4gIFdoeT8KClRoaW5rIG9mIHRoZSBjYXNlIHdoZXJl IHdlJ3JlIHN1c3BlbmRpbmcgdGhlIGNvbXBsZXRlIHN5c3RlbS4gIElmIHlvdQpnbyByb3VuZCBh bmQgYXN5bmNob25vdXNseSB0cnkgdG8gcnVuIHVzZXJzcGFjZSBzY3JpcHRzLCBjaGFuY2VzIGFy ZQp5b3UnbGwgaGF2ZSB0aGUgQ1BVIGFzbGVlcCBiZWZvcmUgX2FueV8gb2YgdGhlIHNjcmlwdHMg aGF2ZSBydW4sIHdoaWNoCm1lYW5zIChlZykgeW91ciBESENQIGNsaWVudCBjb3VsZG4ndCB0ZWxs IHRoZSBzZXJ2ZXIgdGhhdCBpdHMgcmVsZWFzZWQKaXRzIGFsbG9jYXRpb24uCgpBbHNvLCBzaG91 bGQgd2UgYmUgdGVsbGluZyB1c2Vyc3BhY2UgYWJvdXQgc3VzcGVuZCBiZWZvcmUgd2UgYWN0dWFs bHkKc3VzcGVuZCB0aGUgZGV2aWNlPwoKLS0gClJ1c3NlbGwgS2luZwogTGludXgga2VybmVsICAg IDIuNiBBUk0gTGludXggICAtIGh0dHA6Ly93d3cuYXJtLmxpbnV4Lm9yZy51ay8KIG1haW50YWlu ZXIgb2Y6ICAyLjYgUENNQ0lBICAgICAgLSBodHRwOi8vcGNtY2lhLmFybS5saW51eC5vcmcudWsv CiAgICAgICAgICAgICAgICAgMi42IFNlcmlhbCBjb3JlCgoKLS0tLS0tLS0tLS0tLS0tLS0tLS0t LS0tLS0tLS0tLS0tLS0tLS0tLS0tLS0tLS0tLS0tLS0tLQpUaGlzIFNGLk5ldCBlbWFpbCBpcyBz cG9uc29yZWQgYnk6IE9yYWNsZSAxMGcKR2V0IGNlcnRpZmllZCBvbiB0aGUgaG90dGVzdCB0aGlu ZyBldmVyIHRvIGhpdCB0aGUgbWFya2V0Li4uIE9yYWNsZSAxMGcuIApUYWtlIGFuIE9yYWNsZSAx MGcgY2xhc3Mgbm93LCBhbmQgd2UnbGwgZ2l2ZSB5b3UgdGhlIGV4YW0gRlJFRS4gCmh0dHA6Ly9h ZHMub3Nkbi5jb20vP2FkX2lkMTQ5JmFsbG9jX2lkgTY2Jm9wPWNsaWNrCl9fX19fX19fX19fX19f X19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fCkxpbnV4LWhvdHBsdWctZGV2ZWwgbWFp bGluZyBsaXN0ICBodHRwOi8vbGludXgtaG90cGx1Zy5zb3VyY2Vmb3JnZS5uZXQKTGludXgtaG90 cGx1Zy1kZXZlbEBsaXN0cy5zb3VyY2Vmb3JnZS5uZXQKaHR0cHM6Ly9saXN0cy5zb3VyY2Vmb3Jn ZS5uZXQvbGlzdHMvbGlzdGluZm8vbGludXgtaG90cGx1Zy1kZXZlbA== From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S264980AbUD2VnG (ORCPT ); Thu, 29 Apr 2004 17:43:06 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S264874AbUD2VnG (ORCPT ); Thu, 29 Apr 2004 17:43:06 -0400 Received: from caramon.arm.linux.org.uk ([212.18.232.186]:54539 "EHLO caramon.arm.linux.org.uk") by vger.kernel.org with ESMTP id S264980AbUD2Vms (ORCPT ); Thu, 29 Apr 2004 17:42:48 -0400 Date: Thu, 29 Apr 2004 22:42:43 +0100 From: Russell King To: Todd Poynor Cc: mochel@digitalimplant.org, linux-hotplug-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org Subject: Re: [PATCH] Hotplug for device power state changes Message-ID: <20040429224243.L16407@flint.arm.linux.org.uk> Mail-Followup-To: Todd Poynor , mochel@digitalimplant.org, linux-hotplug-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org References: <20040429202654.GA9971@dhcp193.mvista.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.2.5.1i In-Reply-To: <20040429202654.GA9971@dhcp193.mvista.com>; from tpoynor@mvista.com on Thu, Apr 29, 2004 at 01:26:54PM -0700 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Apr 29, 2004 at 01:26:54PM -0700, Todd Poynor wrote: > A patch to call a hotplug device-power agent when the power state of a > device is modified at runtime (that is, individually via sysfs or by a > driver call, not as part of a system suspend/resume). Allows a power > management application to be informed of changes in device power needs. > This can be useful on platforms with dependencies between system > clock/voltage settings and operation of certain devices (such as > PXA27x), or, for example, on a cell phone where voiceband or network > devices going inactive signals an opportunity to lower platform power > levels to conserve battery life. Note that we should run this synchronously with userspace - ie, wait for the userspace hotplug script to finish executing before moving on to the next device. Why? Think of the case where we're suspending the complete system. If you go round and asynchonously try to run userspace scripts, chances are you'll have the CPU asleep before _any_ of the scripts have run, which means (eg) your DHCP client couldn't tell the server that its released its allocation. Also, should we be telling userspace about suspend before we actually suspend the device? -- Russell King Linux kernel 2.6 ARM Linux - http://www.arm.linux.org.uk/ maintainer of: 2.6 PCMCIA - http://pcmcia.arm.linux.org.uk/ 2.6 Serial core