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Tue, 15 Oct 2024 01:00:37 -0700 (PDT) Received: from [127.0.1.1] ([2a01:cb1d:dc:7e00:d382:b11b:c441:d747]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4313f6c5531sm9962385e9.46.2024.10.15.01.00.35 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 15 Oct 2024 01:00:35 -0700 (PDT) From: Bartosz Golaszewski Date: Tue, 15 Oct 2024 10:00:24 +0200 Subject: [PATCH v2 2/2] gpio: create the /sys/class/gpio mount point with GPIO_SYSFS disabled Precedence: bulk X-Mailing-List: linux-gpio@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Message-Id: <20241015-gpio-class-mountpoint-v2-2-7709301876ef@linaro.org> References: <20241015-gpio-class-mountpoint-v2-0-7709301876ef@linaro.org> In-Reply-To: <20241015-gpio-class-mountpoint-v2-0-7709301876ef@linaro.org> To: Greg Kroah-Hartman , "Rafael J. Wysocki" , Linus Walleij , Bartosz Golaszewski , Kent Gibson Cc: linux-kernel@vger.kernel.org, linux-gpio@vger.kernel.org, Bartosz Golaszewski X-Mailer: b4 0.13.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=2478; i=bartosz.golaszewski@linaro.org; h=from:subject:message-id; bh=IXI8fc+BDTt6dXc2mOvzUU5JFVJWsj1fSNvXX0TFXLM=; b=owEBbQKS/ZANAwAKARGnLqAUcddyAcsmYgBnDiEh5aNPWbyBm1yyVv5fwe+71Vy7kKpSsdVtR gVh96Hn7ISJAjMEAAEKAB0WIQQWnetsC8PEYBPSx58Rpy6gFHHXcgUCZw4hIQAKCRARpy6gFHHX cpCtD/4oUNtfzUWGhirGZ4x++US0pfxpEH5QMOPfP0IxjxVRDIuZg68Es3A9Tk9/ZIdWpJbXX0z zcqpXca1REK0CHdUqzBJ2NKLJOiuAijNLdutzgU8VOXjuP+sYjuj1C/Gnuu3Ib2TDqzuWCEcyZ/ uJN9iPVhPovAoPG2+UQh+RlUhkCrJFdWg68L3IVIS9XPoy2JzGx8iTt75iXNZ9ZjKy+Rna/xMa6 3tU1Y4R/TkRNleiYrTjAYCb12AzJHO2zttfW2TvT4WIWhtMmXXSXJ9zot1Xy4i1jy3wqS4XzrrQ /uptNGwcKC2TQkOP64UuvVhnbKz8HZ70Pmf2hEmYuE4i0JOe1lu5N9CnlRQyBvNyGZLmYRf04kU HwcnHgucRg5A+h718QrPRQHpsGoHwnawi4/zoHrmuBMOdjxmYp74OIs34jeSJuXozkbhy+fq2Am q7g1SIrSB1ShuRfO6vzYu30sQBFpwzgn3WHT9IXzKTni8w1KUywjjuIvqq6skY6TyC/aIfqBgm+ NV7ybIAcTCAxaAumuIdztwVKnuBdSHJt2Z1j6kgoc9/6fy9Youp9OIyGEVA2T5HycAj524kvh1K 7JJOK8k6/1zW44PX8t9hTjscmYxX9OsPB23PIDe2KsIELOeriX35+JydtV//1a/q7b7aZDIw4/R +j0ST1Cv3QHC9bw== X-Developer-Key: i=bartosz.golaszewski@linaro.org; a=openpgp; fpr=169DEB6C0BC3C46013D2C79F11A72EA01471D772 From: Bartosz Golaszewski User-space may want to use some kind of a compatibility layer for the deprecated GPIO sysfs ABI. This would typically involve mounting a fuse-based filesystem using the GPIO character device to emulate the sysfs behavior and layout. With GPIO_SYSFS disabled, the /sys/class/gpio directory doesn't exist and user-space cannot create it. In order to facilitate moving away from the sysfs, add a new Kconfig option that indicates to GPIOLIB that is should create an always-empty directory where the GPIO class interface would exist and enable this option by default if GPIO_SYSFS is not selected. Signed-off-by: Bartosz Golaszewski --- drivers/gpio/Kconfig | 18 ++++++++++++++++++ drivers/gpio/gpiolib.c | 6 ++++++ 2 files changed, 24 insertions(+) diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig index efddc6455315..1a3535bda779 100644 --- a/drivers/gpio/Kconfig +++ b/drivers/gpio/Kconfig @@ -69,6 +69,24 @@ config GPIO_SYSFS use the character device /dev/gpiochipN with the appropriate ioctl() operations instead. +config GPIO_SYSFS_CLASS_MOUNT_POINT + bool "Create empty /sys/class/gpio directory" if EXPERT + depends on !GPIO_SYSFS + default y + help + Say Y here to create an empty /sys/class/gpio directory. + + User-space may want to use some kind of a compatibility layer for the + deprecated GPIO sysfs ABI. This would typically involve mounting + a fuse-based filesystem using the GPIO character device to emulate + the sysfs behavior and layout. + + This option makes GPIOLIB create an empty directory at /sys/class/gpio + where user-space can mount the sysfs replacement and avoid having to + change existing programs to adjust to different filesystem paths. + + If unsure, say Y. + config GPIO_CDEV bool prompt "Character device (/dev/gpiochipN) support" if EXPERT diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c index 97346b746ef5..1c8bd765d8e1 100644 --- a/drivers/gpio/gpiolib.c +++ b/drivers/gpio/gpiolib.c @@ -4899,6 +4899,12 @@ static int __init gpiolib_dev_init(void) return ret; } +#if IS_ENABLED(CONFIG_GPIO_SYSFS_CLASS_MOUNT_POINT) + ret = sysfs_create_mount_point(class_kobj, "gpio"); + if (ret) + pr_err("gpiolib: failed to create the GPIO class mountpoint\n"); +#endif /* CONFIG_GPIO_SYSFS_CLASS_MOUNT_POINT */ + gpiolib_initialized = true; gpiochip_setup_devs();