From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dmitry Torokhov Subject: Re: [PATCH 1/3] HID: logitech-hidpp: use devres to manage FF private data Date: Fri, 11 Oct 2019 14:11:08 -0700 Message-ID: <20191011211108.GI229325@dtor-ws> References: <20191007051240.4410-1-andrew.smirnov@gmail.com> <20191007051240.4410-2-andrew.smirnov@gmail.com> <20191011182617.GE229325@dtor-ws> <20191011203303.GF229325@dtor-ws> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: Andrey Smirnov Cc: Benjamin Tissoires , "open list:HID CORE LAYER" , Jiri Kosina , Henrik Rydberg , Sam Bazely , "Pierre-Loup A . Griffais" , Austin Palmer , lkml , "3.8+" List-Id: linux-input@vger.kernel.org On Fri, Oct 11, 2019 at 02:02:30PM -0700, Andrey Smirnov wrote: > On Fri, Oct 11, 2019 at 1:33 PM Dmitry Torokhov > wrote: > > > > On Fri, Oct 11, 2019 at 09:25:52PM +0200, Benjamin Tissoires wrote: > > > On Fri, Oct 11, 2019 at 8:26 PM Dmitry Torokhov > > > wrote: > > > > > > > > On Fri, Oct 11, 2019 at 04:52:04PM +0200, Benjamin Tissoires wrote: > > > > > Hi Andrey, > > > > > > > > > > On Mon, Oct 7, 2019 at 7:13 AM Andrey Smirnov wrote: > > > > > > > > > > > > To simplify resource management in commit that follows as well as to > > > > > > save a couple of extra kfree()s and simplify hidpp_ff_deinit() switch > > > > > > driver code to use devres to manage the life-cycle of FF private data. > > > > > > > > > > > > Signed-off-by: Andrey Smirnov > > > > > > Cc: Jiri Kosina > > > > > > Cc: Benjamin Tissoires > > > > > > Cc: Henrik Rydberg > > > > > > Cc: Sam Bazely > > > > > > Cc: Pierre-Loup A. Griffais > > > > > > Cc: Austin Palmer > > > > > > Cc: linux-input@vger.kernel.org > > > > > > Cc: linux-kernel@vger.kernel.org > > > > > > Cc: stable@vger.kernel.org > > > > > > > > > > This patch doesn't seem to fix any error, is there a reason to send it > > > > > to stable? (besides as a dependency of the rest of the series). > > > > > > > > > > > --- > > > > > > drivers/hid/hid-logitech-hidpp.c | 53 +++++++++++++++++--------------- > > > > > > 1 file changed, 29 insertions(+), 24 deletions(-) > > > > > > > > > > > > diff --git a/drivers/hid/hid-logitech-hidpp.c b/drivers/hid/hid-logitech-hidpp.c > > > > > > index 0179f7ed77e5..58eb928224e5 100644 > > > > > > --- a/drivers/hid/hid-logitech-hidpp.c > > > > > > +++ b/drivers/hid/hid-logitech-hidpp.c > > > > > > @@ -2079,6 +2079,11 @@ static void hidpp_ff_destroy(struct ff_device *ff) > > > > > > struct hidpp_ff_private_data *data = ff->private; > > > > > > > > > > > > kfree(data->effect_ids); > > > > > > > > > > Is there any reasons we can not also devm alloc data->effect_ids? > > > > > > > > > > > + /* > > > > > > + * Set private to NULL to prevent input_ff_destroy() from > > > > > > + * freeing our devres allocated memory > > > > > > > > > > Ouch. There is something wrong here: input_ff_destroy() calls > > > > > kfree(ff->private), when the data has not been allocated by > > > > > input_ff_create(). This seems to lack a little bit of symmetry. > > > > > > > > Yeah, ff and ff-memless essentially take over the private data assigned > > > > to them. They were done before devm and the lifetime of the "private" > > > > data pieces was tied to the lifetime of the input device to simplify > > > > error handling and teardown. > > > > > > Yeah, that stealing of the pointer is not good :) > > > But OTOH, it helps > > > > > > > > > > > Maybe we should clean it up a bit... I'm open to suggestions. > > > > > > The problem I had when doing the review was that there is no easy way > > > to have a "devm_input_ff_create_()", because the way it's built is > > > already "devres-compatible": the destroy gets called by input core. > > > > I do not think we want devm_input_ff_create() explicitly, I think the > > fact that you can "build up" an input device by allocating it, then > > adding slots, poller, ff support, etc, and input core cleans it up is > > all good. It is just the ownership if the driver-private data block is > > not very obvious and is not compatible with allocating via devm. > > > > What do you think of creating input_ff_create_with_private() which > would take a pointer to private memory and set a new > "borrowed_private" flag in struct ff_device which input_ff_destroy() > can check to determine if it needs to free ->private or not? >>From my quick check we only have 3 users of ff->private in the tree: dtor@dtor-ws:~/kernel/master (next)$ git grep -l "[^a-z]ff\->private" -- drivers/ drivers/hid/hid-logitech-hidpp.c drivers/hid/usbhid/hid-pidff.c drivers/input/ff-core.c drivers/input/ff-memless.c and I really wonder if we actually need to have this pointer and maintain it, given that logitech driver appears to not needing it that much... Thanks. -- Dmitry 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=-8.3 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=unavailable 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 8294AECE58D for ; Fri, 11 Oct 2019 21:11:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4A43F2084C for ; Fri, 11 Oct 2019 21:11:16 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="Jvz7fllx" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726642AbfJKVLM (ORCPT ); Fri, 11 Oct 2019 17:11:12 -0400 Received: from mail-pg1-f193.google.com ([209.85.215.193]:40949 "EHLO mail-pg1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726281AbfJKVLM (ORCPT ); Fri, 11 Oct 2019 17:11:12 -0400 Received: by mail-pg1-f193.google.com with SMTP id d26so6474642pgl.7; Fri, 11 Oct 2019 14:11:11 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=N/BP0N83P9W6C5BiVurtFofWl2LpQAdIEXVffsFrPG0=; b=Jvz7fllxnUivk7XuysEKzxZ5YTNQ6Rnby5iUz7DXYwFlPT6t8pI+emQddFG4LRBNnc pnVEH1H3VuiSfm/7J6A3Zp2oQ2A4ww6HCks47rmzHy3zRvksVR6xORwoOdQJLWV6Ctxi Mmbzm0RbXTDCXGz+0lfNumxIlxQF1pW+kAppSh2DYjLUtP+wLZRtdnKGLvBsHElZI4QD tpRQxJWoTjK7SsLHIOovlvYs8Bhw9lk08k0oxa/DtvazlexivTycGwK7wHFwZA7ziNrO LzgxBxBXJ5qN/O6VNVOZuy+RqrCx6tfpPiLTtIQpHMLtnDTuow6ycqhk5oT3ccyCO202 CfJg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=N/BP0N83P9W6C5BiVurtFofWl2LpQAdIEXVffsFrPG0=; b=Wqsh5VcsHe/vA8gbVYxMN7K2oZZjjRgq9dd/Rh84aHK1+ioRG/4UVAH6juCvobYEYM 3XP++LIyelTeomsQ4szlYhBgiIjUb1sM+UegBzfy/ynFWURUnZfdmRJ6OLTzeMVkkQjR 0uHFMn3ScgpEv0mKA64n5pSgUaChSxtgW1l4Mch7zV/ZljhuxGLM08uK8bB1fGLyusNN cTjF6a1CHROuUV517TFG8Fp0FZXQyVyMEIHSCrB2e3482XTsFBgnK8ZuHxqxQyg7YIdG qvNJd7yqqMdPQ/d9S18fBd5U9By96sZNg8pOl8YdntaXiHQ/pTVVBOLaIhMnyUTWWOp8 SG6Q== X-Gm-Message-State: APjAAAUAPFbFNjt8dR5vJYwuNE7Q9732Jmvpvni2erqbjtLitAdAuGPv /8AKaBhdq1nCPK4GaH8Rvy8= X-Google-Smtp-Source: APXvYqzhv6flsAhpHdwLEGMmVOZFh1tfFN/F71S9nwRpqxPCPj1PaB+NyIbIpTED4qh8clbYcS8Hcg== X-Received: by 2002:a17:90a:8a04:: with SMTP id w4mr18356273pjn.135.1570828271058; Fri, 11 Oct 2019 14:11:11 -0700 (PDT) Received: from dtor-ws ([2620:15c:202:201:3adc:b08c:7acc:b325]) by smtp.gmail.com with ESMTPSA id e6sm12873050pfl.146.2019.10.11.14.11.10 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 11 Oct 2019 14:11:10 -0700 (PDT) Date: Fri, 11 Oct 2019 14:11:08 -0700 From: Dmitry Torokhov To: Andrey Smirnov Cc: Benjamin Tissoires , "open list:HID CORE LAYER" , Jiri Kosina , Henrik Rydberg , Sam Bazely , "Pierre-Loup A . Griffais" , Austin Palmer , lkml , "3.8+" Subject: Re: [PATCH 1/3] HID: logitech-hidpp: use devres to manage FF private data Message-ID: <20191011211108.GI229325@dtor-ws> References: <20191007051240.4410-1-andrew.smirnov@gmail.com> <20191007051240.4410-2-andrew.smirnov@gmail.com> <20191011182617.GE229325@dtor-ws> <20191011203303.GF229325@dtor-ws> MIME-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-input-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-input@vger.kernel.org Message-ID: <20191011211108._PRCnB-20K1avDxXuLLCnnJP0Rmf2HzyrA0oGJZLN5E@z> On Fri, Oct 11, 2019 at 02:02:30PM -0700, Andrey Smirnov wrote: > On Fri, Oct 11, 2019 at 1:33 PM Dmitry Torokhov > wrote: > > > > On Fri, Oct 11, 2019 at 09:25:52PM +0200, Benjamin Tissoires wrote: > > > On Fri, Oct 11, 2019 at 8:26 PM Dmitry Torokhov > > > wrote: > > > > > > > > On Fri, Oct 11, 2019 at 04:52:04PM +0200, Benjamin Tissoires wrote: > > > > > Hi Andrey, > > > > > > > > > > On Mon, Oct 7, 2019 at 7:13 AM Andrey Smirnov wrote: > > > > > > > > > > > > To simplify resource management in commit that follows as well as to > > > > > > save a couple of extra kfree()s and simplify hidpp_ff_deinit() switch > > > > > > driver code to use devres to manage the life-cycle of FF private data. > > > > > > > > > > > > Signed-off-by: Andrey Smirnov > > > > > > Cc: Jiri Kosina > > > > > > Cc: Benjamin Tissoires > > > > > > Cc: Henrik Rydberg > > > > > > Cc: Sam Bazely > > > > > > Cc: Pierre-Loup A. Griffais > > > > > > Cc: Austin Palmer > > > > > > Cc: linux-input@vger.kernel.org > > > > > > Cc: linux-kernel@vger.kernel.org > > > > > > Cc: stable@vger.kernel.org > > > > > > > > > > This patch doesn't seem to fix any error, is there a reason to send it > > > > > to stable? (besides as a dependency of the rest of the series). > > > > > > > > > > > --- > > > > > > drivers/hid/hid-logitech-hidpp.c | 53 +++++++++++++++++--------------- > > > > > > 1 file changed, 29 insertions(+), 24 deletions(-) > > > > > > > > > > > > diff --git a/drivers/hid/hid-logitech-hidpp.c b/drivers/hid/hid-logitech-hidpp.c > > > > > > index 0179f7ed77e5..58eb928224e5 100644 > > > > > > --- a/drivers/hid/hid-logitech-hidpp.c > > > > > > +++ b/drivers/hid/hid-logitech-hidpp.c > > > > > > @@ -2079,6 +2079,11 @@ static void hidpp_ff_destroy(struct ff_device *ff) > > > > > > struct hidpp_ff_private_data *data = ff->private; > > > > > > > > > > > > kfree(data->effect_ids); > > > > > > > > > > Is there any reasons we can not also devm alloc data->effect_ids? > > > > > > > > > > > + /* > > > > > > + * Set private to NULL to prevent input_ff_destroy() from > > > > > > + * freeing our devres allocated memory > > > > > > > > > > Ouch. There is something wrong here: input_ff_destroy() calls > > > > > kfree(ff->private), when the data has not been allocated by > > > > > input_ff_create(). This seems to lack a little bit of symmetry. > > > > > > > > Yeah, ff and ff-memless essentially take over the private data assigned > > > > to them. They were done before devm and the lifetime of the "private" > > > > data pieces was tied to the lifetime of the input device to simplify > > > > error handling and teardown. > > > > > > Yeah, that stealing of the pointer is not good :) > > > But OTOH, it helps > > > > > > > > > > > Maybe we should clean it up a bit... I'm open to suggestions. > > > > > > The problem I had when doing the review was that there is no easy way > > > to have a "devm_input_ff_create_()", because the way it's built is > > > already "devres-compatible": the destroy gets called by input core. > > > > I do not think we want devm_input_ff_create() explicitly, I think the > > fact that you can "build up" an input device by allocating it, then > > adding slots, poller, ff support, etc, and input core cleans it up is > > all good. It is just the ownership if the driver-private data block is > > not very obvious and is not compatible with allocating via devm. > > > > What do you think of creating input_ff_create_with_private() which > would take a pointer to private memory and set a new > "borrowed_private" flag in struct ff_device which input_ff_destroy() > can check to determine if it needs to free ->private or not? >From my quick check we only have 3 users of ff->private in the tree: dtor@dtor-ws:~/kernel/master (next)$ git grep -l "[^a-z]ff\->private" -- drivers/ drivers/hid/hid-logitech-hidpp.c drivers/hid/usbhid/hid-pidff.c drivers/input/ff-core.c drivers/input/ff-memless.c and I really wonder if we actually need to have this pointer and maintain it, given that logitech driver appears to not needing it that much... Thanks. -- Dmitry