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Received: from shell.armlinux.org.uk ([2001:4d48:ad52:3201:5054:ff:fe00:4ec]:40348) by pandora.armlinux.org.uk with esmtpsa (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.90_1) (envelope-from ) id 1ifPHr-000791-JH; Thu, 12 Dec 2019 14:17:51 +0000 Received: from linux by shell.armlinux.org.uk with local (Exim 4.92) (envelope-from ) id 1ifPHn-0006sN-Ar; Thu, 12 Dec 2019 14:17:47 +0000 Date: Thu, 12 Dec 2019 14:17:47 +0000 From: Russell King - ARM Linux admin To: Marc Gonzalez Subject: Re: [PATCH v1] clk: Convert managed get functions to devm_add_action API Message-ID: <20191212141747.GI25745@shell.armlinux.org.uk> References: <3d8a58bf-0814-1ec1-038a-10a20b9646ad@free.fr> <20191128185630.GK82109@yoga> <20191202014237.GR248138@dtor-ws> <20191211222829.GV50317@dtor-ws> <70528f77-ca10-01cd-153b-23486ce87d45@free.fr> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <70528f77-ca10-01cd-153b-23486ce87d45@free.fr> User-Agent: Mutt/1.10.1 (2018-07-13) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20191212_061814_120496_4364165C X-CRM114-Status: GOOD ( 20.37 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Kuninori Morimoto , Stephen Boyd , Michael Turquette , Dmitry Torokhov , linux-clk , LKML , Bjorn Andersson , Linux ARM , Robin Murphy , Sudip Mukherjee , Guenter Roeck Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Thu, Dec 12, 2019 at 02:53:40PM +0100, Marc Gonzalez wrote: > On 11/12/2019 23:28, Dmitry Torokhov wrote: > > > On Wed, Dec 11, 2019 at 05:17:28PM +0100, Marc Gonzalez wrote: > > > >> What is the rationale for the devm_add_action API? > > > > For one-off and maybe complex unwind actions in drivers that wish to use > > devm API (as mixing devm and manual release is verboten). Also is often > > used when some core subsystem does not provide enough devm APIs. > > Thanks for the insight, Dmitry. Thanks to Robin too. > > This is what I understand so far: > > devm_add_action() is nice because it hides/factorizes the complexity > of the devres API, but it incurs a small storage overhead of one > pointer per call, which makes it unfit for frequently used actions, > such as clk_get. > > Is that correct? > > My question is: why not design the API without the small overhead? > > Proof of concept below: > > > diff --git a/drivers/base/devres.c b/drivers/base/devres.c > index 0bbb328bd17f..76392dd6273b 100644 > --- a/drivers/base/devres.c > +++ b/drivers/base/devres.c > @@ -685,6 +685,20 @@ int devres_release_group(struct device *dev, void *id) > } > EXPORT_SYMBOL_GPL(devres_release_group); > > +void *devm_add(struct device *dev, dr_release_t func, void *arg, size_t size) > +{ > + void *data = devres_alloc(func, size, GFP_KERNEL); > + > + if (data) { > + memcpy(data, arg, size); > + devres_add(dev, data); > + } else > + func(dev, arg); > + > + return data; > +} > +EXPORT_SYMBOL_GPL(devm_add); > + > /* > * Custom devres actions allow inserting a simple function call > * into the teadown sequence. > diff --git a/drivers/clk/clk-devres.c b/drivers/clk/clk-devres.c > index be160764911b..8db671823126 100644 > --- a/drivers/clk/clk-devres.c > +++ b/drivers/clk/clk-devres.c > @@ -4,6 +4,11 @@ > #include > #include > > +static void __clk_put(struct device *dev, void *data) > +{ > + clk_put(*(struct clk **)data); > +} > + > static void devm_clk_release(struct device *dev, void *res) > { > clk_put(*(struct clk **)res); > @@ -11,19 +16,11 @@ static void devm_clk_release(struct device *dev, void *res) > > struct clk *devm_clk_get(struct device *dev, const char *id) > { > - struct clk **ptr, *clk; > - > - ptr = devres_alloc(devm_clk_release, sizeof(*ptr), GFP_KERNEL); > - if (!ptr) > - return ERR_PTR(-ENOMEM); > + struct clk *clk = clk_get(dev, id); > > - clk = clk_get(dev, id); > - if (!IS_ERR(clk)) { > - *ptr = clk; > - devres_add(dev, ptr); > - } else { > - devres_free(ptr); > - } > + if (!IS_ERR(clk)) > + if (!devm_add(dev, __clk_put, &clk, sizeof(clk))) > + clk = ERR_PTR(-ENOMEM); You leak clk here. -- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTC broadband for 0.8mile line in suburbia: sync at 12.1Mbps down 622kbps up According to speedtest.net: 11.9Mbps down 500kbps up _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel