From patchwork Tue Apr 5 13:54:34 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Marc Zyngier X-Patchwork-Id: 12802072 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 43FA0C4321E for ; Tue, 5 Apr 2022 23:25:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230180AbiDEXD4 (ORCPT ); Tue, 5 Apr 2022 19:03:56 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51086 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1443188AbiDEPjI (ORCPT ); Tue, 5 Apr 2022 11:39:08 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6B1AA14753D; Tue, 5 Apr 2022 06:55:04 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id E6E05B81BA8; Tue, 5 Apr 2022 13:55:02 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7BD12C385A4; Tue, 5 Apr 2022 13:55:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1649166901; bh=iB8V/cO3JDHg3B4uaq4JA6GvE9hxQZX/fsJc7mMx4Fw=; h=From:To:Cc:Subject:Date:From; b=JhEBLwku9Xc18r0NykUeJRpimrF/ZQ7Vy2v5FtpfNKp9TFQV8SCLWd3YfLSCkoZWj nQ5A2lhhzkC2vDDOLS2fLFyRvZxjVweUFNChghZAlbqcrbC8/h9EjHgSTIqsg7fPsj PeJo5uheX/Wkb0siHrvHYvvGdA2KuMrQejv1bwSTdgHD5zpl2zGCmBLKzt55eA8J0v pkg0PsKScqzB51rkSgMMs2UrQqyX27Y4khUssjIy6AAutuC1LSJ9v1DeM7Mr7EI5w6 KSPtZ0NMJGh0sv1+hb63xtf6/ucXGTc65OLTwLgfmFundA1Z7xEP9yqvyzIkQbzuRi QUk3HlObdvTfw== Received: from sofa.misterjones.org ([185.219.108.64] helo=why.lan) by disco-boy.misterjones.org with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94.2) (envelope-from ) id 1nbje7-001q4g-37; Tue, 05 Apr 2022 14:54:59 +0100 From: Marc Zyngier To: linux-kernel@vger.kernel.org Cc: Linus Walleij , Bartosz Golaszewski , Thierry Reding , Joey Gouly , Jonathan Hunter , Hector Martin , Sven Peter , Alyssa Rosenzweig , Bjorn Andersson , Andy Gross , Jeffrey Hugo , Thomas Gleixner , Basavaraj Natikar , Shyam Sundar S K , linux-gpio@vger.kernel.org, linux-tegra@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-arm-msm@vger.kernel.org, kernel-team@android.com Subject: [PATCH v2 00/10] gpiolib: Handle immutable irq_chip structures Date: Tue, 5 Apr 2022 14:54:34 +0100 Message-Id: <20220405135444.199295-1-maz@kernel.org> X-Mailer: git-send-email 2.34.1 MIME-Version: 1.0 X-SA-Exim-Connect-IP: 185.219.108.64 X-SA-Exim-Rcpt-To: linux-kernel@vger.kernel.org, linus.walleij@linaro.org, brgl@bgdev.pl, thierry.reding@gmail.com, joey.gouly@arm.com, jonathanh@nvidia.com, marcan@marcan.st, sven@svenpeter.dev, alyssa@rosenzweig.io, bjorn.andersson@linaro.org, agross@kernel.org, jeffrey.l.hugo@gmail.com, tglx@linutronix.de, Basavaraj.Natikar@amd.com, Shyam-sundar.S-k@amd.com, linux-gpio@vger.kernel.org, linux-tegra@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-arm-msm@vger.kernel.org, kernel-team@android.com X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false Precedence: bulk List-ID: X-Mailing-List: linux-arm-msm@vger.kernel.org This is a followup from [1]. I recently realised that the gpiolib play ugly tricks on the unsuspecting irq_chip structures by patching the callbacks. Not only this breaks when an irq_chip structure is made const (which really should be the default case), but it also forces this structure to be copied at nauseam for each instance of the GPIO block, which is a waste of memory. My current approach is to add a new irq_chip flag (IRQCHIP_IMMUTABLE) which does what it says on the tin: don't you dare writing to them. Gpiolib is further updated not to install its own callbacks, and it becomes the responsibility of the driver to call into the gpiolib when required. This is similar to what we do for other subsystems such as PCI-MSI. 5 drivers are updated to this new model: M1, QC, Tegra, pl061 and AMD (as I actively use them) keeping a single irq_chip structure, marking it const, and exposing the new flag. Nothing breaks, the volume of change is small, the memory usage goes down and we have fewer callbacks that can be used as attack vectors. What's not to love? * From v1 [1]: - pl061 and AMD drivers converted - New helpers to keep the changes small - New warning for non-converted drivers - Documentation and TODO updates [1] https://lore.kernel.org/r/20220223154405.54912-1-maz@kernel.org Marc Zyngier (10): gpio: Don't fiddle with irqchips marked as immutable gpio: Expose the gpiochip_irq_re[ql]res helpers gpio: Add helpers to ease the transition towards immutable irq_chip gpio: tegra186: Make the irqchip immutable gpio: pl061: Make the irqchip immutable pinctrl: apple-gpio: Make the irqchip immutable pinctrl: msmgpio: Make the irqchip immutable pinctrl: amd: Make the irqchip immutable gpio: Update TODO to mention immutable irq_chip structures Documentation: Update the recommended pattern for GPIO irqchips Documentation/driver-api/gpio/driver.rst | 175 ++++++++++++++++++----- drivers/gpio/TODO | 19 +++ drivers/gpio/gpio-pl061.c | 32 +++-- drivers/gpio/gpio-tegra186.c | 32 +++-- drivers/gpio/gpiolib.c | 13 +- drivers/pinctrl/pinctrl-amd.c | 11 +- drivers/pinctrl/pinctrl-apple-gpio.c | 29 ++-- drivers/pinctrl/qcom/pinctrl-msm.c | 53 ++++--- include/linux/gpio/driver.h | 16 +++ include/linux/irq.h | 2 + kernel/irq/debugfs.c | 1 + 11 files changed, 293 insertions(+), 90 deletions(-) Reviewed-by: Andy Shevchenko Reviewed-by: Bartosz Golaszewski Acked-by: Linus Walleij