From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.3 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 65413C32753 for ; Wed, 14 Aug 2019 21:20:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 300F3214C6 for ; Wed, 14 Aug 2019 21:20:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1565817617; bh=2E2JMCEsGfJgUZSIcsEX9gpK1QWJbGLg/k/y//c7LnY=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=XimXrZCd3CZ3OWhwyHfkIHUQkTGa/8L5cxN2OGUndhkPLQ9jkUXIx1eWR22H+Se5u ZbFezIT4gqoEMVsZNAwN1LhBTM0rFJLuC15rrU/QF8Hri+HFVlOoHZb9MS+a3SX0kr gRxhjQcbPmzBWoRazSAEKXgDg/mD/S5hy7+Wb8og= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728378AbfHNVUQ (ORCPT ); Wed, 14 Aug 2019 17:20:16 -0400 Received: from mail.kernel.org ([198.145.29.99]:44786 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728014AbfHNVUQ (ORCPT ); Wed, 14 Aug 2019 17:20:16 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id AEF2A2133F; Wed, 14 Aug 2019 21:20:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1565817615; bh=2E2JMCEsGfJgUZSIcsEX9gpK1QWJbGLg/k/y//c7LnY=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=pgLKdYEea1VQuEuz1Gv3VbFrCYN2PEZ4jEbCkHoJwkSePk2JWz6kFI/uZ+uK+7dMF b0JQUzgonM4/XQ+1OafG24te3op3Ut/QA4FsqW9o6Qw+mMQu+ERyz3OqmgUD4GFDH3 KpH/YdphbCyf+VobkIuFmnck9Dpp+wIQGoT3wL5U= Date: Wed, 14 Aug 2019 23:20:12 +0200 From: Greg Kroah-Hartman To: Nick Crews Cc: linux-usb@vger.kernel.org, Enric Balletbo i Serra , linux-kernel , Daniel Kurtz Subject: Re: Policy to keep USB ports powered in low-power states Message-ID: <20190814212012.GB22618@kroah.com> References: <20190813060249.GD6670@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.12.1 (2019-06-15) Sender: linux-usb-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-usb@vger.kernel.org On Wed, Aug 14, 2019 at 02:12:07PM -0600, Nick Crews wrote: > Thanks for the fast response! > > On Tue, Aug 13, 2019 at 12:02 AM Greg Kroah-Hartman > wrote: > > > > On Mon, Aug 12, 2019 at 06:08:43PM -0600, Nick Crews wrote: > > > Hi Greg! > > > > Hi! > > > > First off, please fix your email client to not send html so that vger > > does not reject your messages :) > > Thanks, should be good now. > > > > > > I am working on a Chrome OS device that supports a policy called "USB Power > > > Share," which allows users to turn the laptop into a charge pack for their > > > phone. When the policy is enabled, power will be supplied to the USB ports > > > even when the system is in low power states such as S3 and S5. When > > > disabled, then no power will be supplied in S3 and S5. I wrote a driver > > > for this already as part > > > of drivers/platform/chrome/, but Enric Balletbo i Serra, the maintainer, > > > had the reasonable suggestion of trying to move this into the USB subsystem. > > > > Correct suggestion. > > > > > Has anything like this been done before? Do you have any preliminary > > > thoughts on this before I start writing code? A few things that I haven't > > > figured out yet: > > > - How to make this feature only available on certain devices. Using device > > > tree? Kconfig? Making a separate driver just for this device that plugs > > > into the USB core? > > > - The feature is only supported on some USB ports, so we need a way of > > > filtering on a per-port basis. > > > > Look at the drivers/usb/typec/ code, I think that should do everything > > you need here as this is a typec standard functionality, right? > > Unfortunately this is for USB 2.0 ports, so it's not type-C. > Is the type-C code still worth looking at? If this is for USB 2, does it use the "non-standard" hub commands to turn on and off power? If so, why not just use the usbreset userspace program for that? And how are you turning a USB 2 port into a power source? That feels really odd given the spec. Is this part of the standard somewhere or just a firmware/hardware hack that you are adding to a device? Is there some port information in the firmware that describes this functionality? If so, can you expose it through sysfs to the port that way? thanks, greg k-h