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=-14.3 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_IN_DEF_DKIM_WL 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 813CACA90AF for ; Wed, 13 May 2020 08:35:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5DDAF20740 for ; Wed, 13 May 2020 08:35:37 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="LGlk4Sox" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732308AbgEMIfg (ORCPT ); Wed, 13 May 2020 04:35:36 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37602 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726092AbgEMIfg (ORCPT ); Wed, 13 May 2020 04:35:36 -0400 Received: from mail-ot1-x343.google.com (mail-ot1-x343.google.com [IPv6:2607:f8b0:4864:20::343]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id CBDA6C061A0C for ; Wed, 13 May 2020 01:35:34 -0700 (PDT) Received: by mail-ot1-x343.google.com with SMTP id d26so1526436otc.7 for ; Wed, 13 May 2020 01:35:34 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=KA7iaRwKyQU/DbW+v3q/rxbvNUjeMSpAhHPzsxnLI+Q=; b=LGlk4SoxCLCmjsHIETakzjhKgymWpgXG0APfAIM+adiGsaVmA2JqFrwoNdNDJ9IsUm vB4oxu6Pzqj2RBazLWSbX9T/Xeli8hHlxESL8IMz2Jzlm9Q6HYiDrwzdFQBGBgJFBTZi j+xed0+XZWTAlHhcRB/ANdUQ/1l7tTGF1a3ME/vE5JFnzi0HUZUxzVap/yWJLrAwHwJY Zcbf+I3vF/ZRjgULoK7RjRdPAj8K4kZVD+bW25oSU/q9nWGDxvDhiGqQq8nLBLlUxhTB InaOO05XJdWTRbkgCglneldx8GLO7kiHwF4MZ+1bBWcDGZ6Sub8fZSe9U1WACqd52Q/e jDfA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=KA7iaRwKyQU/DbW+v3q/rxbvNUjeMSpAhHPzsxnLI+Q=; b=IW7x4NhCwroMFeOOg3VROyGgvQahwbeBXt+T8AP4U/U5u3KQ/9xSyrJZqSZu1yHh+I uEuUUxESszpcu/6hishKz083GPorZQVPQ3wmNtjxIjA0uUPprAdt1Ryv4qqGzx9tBrJa YKGEoQ+bjcZyNi31M7xwzOTPA4fPksigxZ1cFOb4Ufb086mzcFanKmijOpj7bOny0ydI zcITAfh3uR+tB6WqfaVpXlvktpSMGXagPxI21Agyqaw5zXdGd+DwIsMtOL2H451DWj+k A3aQSd3pb43lyYpaeQmEiMJ98mlGnTnJFYRSnnNGYG0r/F9kUZtUO6TEvCXFCX3htC/t 8QYQ== X-Gm-Message-State: AGi0Pub9Cl4e78MC2n76/gdR/zCVDN/Mxn0ws/wNBYDwhkVjQ/PrKvHI TUzaPvCXqXVyD46Ea0VDLBJV+lLcP2lP3u2uh86PJA== X-Google-Smtp-Source: APiQypKG1jpeHPtIYqXqqPvvUODnp63p3EfI9HPjXEK2KnG8KGDQSeKVof0Ng6JuVkmQaNFUyFiIGFFVd5ezUZq5Ldo= X-Received: by 2002:a05:6830:1e45:: with SMTP id e5mr19594675otj.236.1589358933497; Wed, 13 May 2020 01:35:33 -0700 (PDT) MIME-Version: 1.0 References: <20200513013415.148858-1-saravanak@google.com> <20200513082209.GB770255@kroah.com> In-Reply-To: <20200513082209.GB770255@kroah.com> From: Saravana Kannan Date: Wed, 13 May 2020 01:34:57 -0700 Message-ID: Subject: Re: [PATCH v1] driver core: Add state_synced sysfs file for devices that support it To: Greg Kroah-Hartman Cc: "Rafael J. Wysocki" , Android Kernel Team , LKML Content-Type: text/plain; charset="UTF-8" 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 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. > That > will save you lots of housekeeping as well as properly remove the > attribute when the device is removed from the system (which you didn't > explicitly do in this patch...) I had a nagging feeling I was missing something. Duh! I'll make sure I do proper clean up in v2. Thanks for the review. -Saravana