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=-6.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham 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 28B03C433DF for ; Thu, 14 May 2020 06:13:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 00B7C206D8 for ; Thu, 14 May 2020 06:13:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1589436836; bh=bhNOJnYDfB8gOvaKKGeOvSoCEvPi1a1FTJvAij5KE+A=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=FqwSYo6PbN5SdOZ9QXzt1TPTSm88jXaZU+PA3XDQ37tc8He+WRkh2RgsQ0hpfVNHX 3ziSjwk+f7a3RSvf+1WIPkdWb4BB0Q015CI4qYgp282MrBuoq2gLSOuH3DGbMDpcMH 4XVoMEiIEdCxr6VmpZ2wyvmrumQbn39TjV9zKNgc= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725952AbgENGNz (ORCPT ); Thu, 14 May 2020 02:13:55 -0400 Received: from mail.kernel.org ([198.145.29.99]:43376 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725794AbgENGNy (ORCPT ); Thu, 14 May 2020 02:13:54 -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 8C184206D4; Thu, 14 May 2020 06:13:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1589436834; bh=bhNOJnYDfB8gOvaKKGeOvSoCEvPi1a1FTJvAij5KE+A=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=h9QCj7kC4KQdvPhcxy3ChcGQPglBeen/Fit9MrSK368fmbHn+87CbrQJ4pbhT7SZY eW01BmaPLAG48LIlTBjkKvPsBxmF2TpEaTM4VzQoDzhSEzUbvX2tLHcFlscsmRpjKd X+1OxGRRgLo6yruzXP1QewxOTKyLmDtuUwsUG1Fo= Date: Thu, 14 May 2020 08:13:51 +0200 From: Greg Kroah-Hartman To: Saravana Kannan Cc: "Rafael J. Wysocki" , Android Kernel Team , LKML Subject: Re: [PATCH v1] driver core: Add state_synced sysfs file for devices that support it Message-ID: <20200514061351.GB1457703@kroah.com> References: <20200513013415.148858-1-saravanak@google.com> <20200513082209.GB770255@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, May 13, 2020 at 11:49:57AM -0700, Saravana Kannan wrote: > On Wed, May 13, 2020 at 1:34 AM Saravana Kannan wrote: > > > > On Wed, May 13, 2020 at 1:22 AM Greg Kroah-Hartman > > wrote: > > > > > > On Tue, May 12, 2020 at 06:34:15PM -0700, Saravana Kannan wrote: > > > > This can be used to check if a device supports sync_state() callbacks > > > > and therefore keeps resources left on by the bootloader enabled till all > > > > its consumers have probed. > > > > > > > > This can also be used to check if sync_state() has been called for a > > > > device or whether it is still trying to keep resources enabled because > > > > they were left enabled by the bootloader and all its consumers haven't > > > > probed yet. > > > > > > > > Signed-off-by: Saravana Kannan > > > > --- > > > > .../ABI/testing/sysfs-devices-state_synced | 24 +++++++++++++++++++ > > > > drivers/base/dd.c | 16 +++++++++++++ > > > > 2 files changed, 40 insertions(+) > > > > create mode 100644 Documentation/ABI/testing/sysfs-devices-state_synced > > > > > > > > diff --git a/Documentation/ABI/testing/sysfs-devices-state_synced b/Documentation/ABI/testing/sysfs-devices-state_synced > > > > new file mode 100644 > > > > index 000000000000..0c922d7d02fc > > > > --- /dev/null > > > > +++ b/Documentation/ABI/testing/sysfs-devices-state_synced > > > > @@ -0,0 +1,24 @@ > > > > +What: /sys/devices/.../state_synced > > > > +Date: May 2020 > > > > +Contact: Saravana Kannan > > > > +Description: > > > > + The /sys/devices/.../state_synced attribute is only present for > > > > + devices whose bus types or driver provides the .sync_state() > > > > + callback. The number read from it (0 or 1) reflects the value > > > > + of the device's 'state_synced' field. A value of 0 means the > > > > + .sync_state() callback hasn't been called yet. A value of 1 > > > > + means the .sync_state() callback has been called. > > > > + > > > > + Generally, if a device has sync_state() support and has some of > > > > + the resources it provides enabled at the time the kernel starts > > > > + (Eg: enabled by hardware reset or bootloader or anything that > > > > + run before the kernel starts), then it'll keep those resources > > > > + enabled and in a state that's compatible with the state they > > > > + were in at the start of the kernel. The device will stop doing > > > > + this only when the sync_state() callback has been called -- > > > > + which happens only when all its consumer devices are registered > > > > + and have probed successfully. Resources that were left disabled > > > > + at the time the kernel starts are not affected or limited in > > > > + any way by sync_state() callbacks. > > > > + > > > > + > > > > diff --git a/drivers/base/dd.c b/drivers/base/dd.c > > > > index 48ca81cb8ebc..72599436ae84 100644 > > > > --- a/drivers/base/dd.c > > > > +++ b/drivers/base/dd.c > > > > @@ -458,6 +458,13 @@ static void driver_deferred_probe_add_trigger(struct device *dev, > > > > driver_deferred_probe_trigger(); > > > > } > > > > > > > > +static ssize_t state_synced_show(struct device *dev, > > > > + struct device_attribute *attr, char *buf) > > > > +{ > > > > + return sprintf(buf, "%u\n", dev->state_synced); > > > > +} > > > > +static DEVICE_ATTR_RO(state_synced); > > > > + > > > > static int really_probe(struct device *dev, struct device_driver *drv) > > > > { > > > > int ret = -EPROBE_DEFER; > > > > @@ -531,9 +538,16 @@ static int really_probe(struct device *dev, struct device_driver *drv) > > > > goto dev_groups_failed; > > > > } > > > > > > > > + if (dev_has_sync_state(dev) && > > > > + device_create_file(dev, &dev_attr_state_synced)) { > > > > + dev_err(dev, "state_synced sysfs add failed\n"); > > > > + goto dev_sysfs_state_synced_failed; > > > > + } > > > > > > Why not add this to the groups above this and only enable it if needed > > > at runtime? > > > > Those groups above seem to be driver specific groups. Looking at the > > code, some drivers seem to be setting them. Also, this attribute can > > only be decided after a driver has successfully bound to the device > > because dev_has_sync_state() has to check the bus and the driver for > > sync_state() support. > > > > > The is_visible() callback should be what you need to use here. > > > > If this is an attribute specific property, it might work. I'll take a look. > > I took a look at is_visible(). It only makes sense for a group of > attributes that are exposed in a sub directory. But state_synced is a > top level property IMO. What I'm doing is similar to the "online" > attribute that's exposed for a device. No, no need for a subdirectory for an attribute group. If you don't have a name for the group, the files will be placed in the device's directory. > And even if I create a group with one lone attribute, I'll still have > to add it after the device has probed or have to call > sysfs_update_groups() after the device is probed to update the > visibility. Seems quite messy and unnecessarily complicated. Ah, ok, that is messier. > I'd like to keep this an attribute and not create a group for that > reason. Does that sound okay to you? I'll obviously still do the clean > up correctly. Ok, that's fine, we can change it later if we figure it out. thanks, greg k-h