From fdf9cab5eaa849e90b12e17718bc47130a91433c Mon Sep 17 00:00:00 2001 From: Jonathan Bell Date: Tue, 25 Apr 2023 15:52:13 +0100 Subject: [PATCH] drivers: char: add generic gpiomem driver Based on bcm2835-gpiomem. We allow export of the "GPIO registers" to userspace via a chardev as this allows for finer access control (e.g. users must be group gpio, root not required). This driver allows access to either rp1-gpiomem or gpiomem, depending on which nodes are populated in devicetree. RP1 has a different look-and-feel to BCM283x SoCs as it has split ranges for IO controls and the parallel registered OE/IN/OUT access. To handle this, the driver concatenates the ranges for an IO bank and the corresponding RIO instance into a contiguous buffer. Signed-off-by: Jonathan Bell --- drivers/char/Kconfig | 8 + drivers/char/Makefile | 1 + drivers/char/raspberrypi-gpiomem.c | 276 +++++++++++++++++++++++++++++ 3 files changed, 285 insertions(+) create mode 100644 drivers/char/raspberrypi-gpiomem.c --- a/drivers/char/Kconfig +++ b/drivers/char/Kconfig @@ -461,4 +461,12 @@ config RANDOM_TRUST_BOOTLOADER believe its RNG facilities may be faulty. This may also be configured at boot time with "random.trust_bootloader=on/off". +config RASPBERRYPI_GPIOMEM + tristate "Rootless GPIO access via mmap() on Raspberry Pi boards" + default n + help + Provides users with root-free access to the GPIO registers + on the board. Calling mmap(/dev/gpiomem) will map the GPIO + register page to the user's pointer. + endmenu --- a/drivers/char/Makefile +++ b/drivers/char/Makefile @@ -46,3 +46,4 @@ obj-$(CONFIG_XILLYBUS_CLASS) += xillybus obj-$(CONFIG_POWERNV_OP_PANEL) += powernv-op-panel.o obj-$(CONFIG_ADI) += adi.o obj-$(CONFIG_BRCM_CHAR_DRIVERS) += broadcom/ +obj-$(CONFIG_RASPBERRYPI_GPIOMEM) += raspberrypi-gpiomem.o --- /dev/null +++ b/drivers/char/raspberrypi-gpiomem.c @@ -0,0 +1,276 @@ +// SPDX-License-Identifier: GPL-2.0 OR BSD-3-Clause +/** + * raspberrypi-gpiomem.c + * + * Provides MMIO access to discontiguous section of Device memory as a linear + * user mapping. Successor to bcm2835-gpiomem.c. + * + * Copyright (c) 2023, Raspberry Pi Ltd. + */ + +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#define DRIVER_NAME "rpi-gpiomem" +#define DEVICE_MINOR 0 + +/* + * Sensible max for a hypothetical "gpio" controller that splits pads, + * IO controls, GPIO in/out/enable, and function selection into different + * ranges. Most use only one or two. + */ +#define MAX_RANGES 4 + +struct io_windows { + unsigned long phys_base; + unsigned long len; +}; + +struct rpi_gpiomem_priv { + dev_t devid; + struct class *class; + struct cdev rpi_gpiomem_cdev; + struct device *dev; + const char *name; + unsigned int nr_wins; + struct io_windows iowins[4]; +}; + +static int rpi_gpiomem_open(struct inode *inode, struct file *file) +{ + int dev = iminor(inode); + int ret = 0; + struct rpi_gpiomem_priv *priv; + + if (dev != DEVICE_MINOR) + ret = -ENXIO; + + priv = container_of(inode->i_cdev, struct rpi_gpiomem_priv, + rpi_gpiomem_cdev); + if (!priv) + return -EINVAL; + file->private_data = priv; + return ret; +} + +static int rpi_gpiomem_release(struct inode *inode, struct file *file) +{ + int dev = iminor(inode); + int ret = 0; + + if (dev != DEVICE_MINOR) + ret = -ENXIO; + + return ret; +} + +static const struct vm_operations_struct rpi_gpiomem_vm_ops = { +#ifdef CONFIG_HAVE_IOREMAP_PROT + .access = generic_access_phys +#endif +}; + +static int rpi_gpiomem_mmap(struct file *file, struct vm_area_struct *vma) +{ + int i; + struct rpi_gpiomem_priv *priv; + unsigned long base; + unsigned long len = 0; + unsigned long offset; + + priv = file->private_data; + /* + * Userspace must provide a virtual address space at least + * the size of the concatenated ranges. + */ + for (i = 0; i < priv->nr_wins; i++) + len += priv->iowins[i].len; + if (len > vma->vm_end - vma->vm_start + 1) + return -EINVAL; + + vma->vm_ops = &rpi_gpiomem_vm_ops; + offset = vma->vm_start; + for (i = 0; i < priv->nr_wins; i++) { + base = priv->iowins[i].phys_base >> PAGE_SHIFT; + len = priv->iowins[i].len; + vma->vm_page_prot = phys_mem_access_prot(file, base, len, + vma->vm_page_prot); + if (remap_pfn_range(vma, offset, + base, len, + vma->vm_page_prot)) + break; + offset += len; + } + + if (i < priv->nr_wins) + return -EAGAIN; + + return 0; +} + +static const struct file_operations rpi_gpiomem_fops = { + .owner = THIS_MODULE, + .open = rpi_gpiomem_open, + .release = rpi_gpiomem_release, + .mmap = rpi_gpiomem_mmap, +}; + +static const struct of_device_id rpi_gpiomem_of_match[]; + +static int rpi_gpiomem_probe(struct platform_device *pdev) +{ + int err, i; + const struct of_device_id *id; + struct device *dev = &pdev->dev; + struct device_node *node = dev->of_node; + struct resource *ioresource; + struct rpi_gpiomem_priv *priv; + + /* Allocate buffers and instance data */ + + priv = kzalloc(sizeof(struct rpi_gpiomem_priv), GFP_KERNEL); + + if (!priv) { + err = -ENOMEM; + goto failed_inst_alloc; + } + platform_set_drvdata(pdev, priv); + + priv->dev = dev; + id = of_match_device(rpi_gpiomem_of_match, dev); + if (!id) + return -EINVAL; + + /* + * Device node naming - for legacy (bcm2835) DT bindings, the driver + * created the node based on a hardcoded name - for new bindings, + * take the node name from DT. + */ + if (id == &rpi_gpiomem_of_match[0]) { + priv->name = "gpiomem"; + } else { + err = of_property_read_string(node, "chardev-name", &priv->name); + if (err) + return -EINVAL; + } + + /* + * Go find the register ranges associated with this instance + */ + for (i = 0; i < MAX_RANGES; i++) { + ioresource = platform_get_resource(pdev, IORESOURCE_MEM, i); + if (!ioresource && i == 0) { + dev_err(priv->dev, "failed to get IO resource - no ranges available\n"); + err = -ENOENT; + goto failed_get_resource; + } + if (!ioresource) + break; + + priv->iowins[i].phys_base = ioresource->start; + priv->iowins[i].len = (ioresource->end + 1) - ioresource->start; + dev_info(&pdev->dev, "window base 0x%08lx size 0x%08lx\n", + priv->iowins[i].phys_base, priv->iowins[i].len); + priv->nr_wins++; + } + + /* Create character device entries */ + + err = alloc_chrdev_region(&priv->devid, + DEVICE_MINOR, 1, priv->name); + if (err != 0) { + dev_err(priv->dev, "unable to allocate device number"); + goto failed_alloc_chrdev; + } + cdev_init(&priv->rpi_gpiomem_cdev, &rpi_gpiomem_fops); + priv->rpi_gpiomem_cdev.owner = THIS_MODULE; + err = cdev_add(&priv->rpi_gpiomem_cdev, priv->devid, 1); + if (err != 0) { + dev_err(priv->dev, "unable to register device"); + goto failed_cdev_add; + } + + /* Create sysfs entries */ + + priv->class = class_create(THIS_MODULE, priv->name); + if (IS_ERR(priv->class)) { + err = PTR_ERR(priv->class); + goto failed_class_create; + } + + dev = device_create(priv->class, NULL, priv->devid, NULL, priv->name); + if (IS_ERR(dev)) { + err = PTR_ERR(dev); + goto failed_device_create; + } + + dev_info(priv->dev, "initialised %u regions as /dev/%s\n", + priv->nr_wins, priv->name); + + return 0; + +failed_device_create: + class_destroy(priv->class); +failed_class_create: + cdev_del(&priv->rpi_gpiomem_cdev); +failed_cdev_add: + unregister_chrdev_region(priv->devid, 1); +failed_alloc_chrdev: +failed_get_resource: + kfree(priv); +failed_inst_alloc: + dev_err(&pdev->dev, "could not load rpi_gpiomem"); + return err; +} + +static int rpi_gpiomem_remove(struct platform_device *pdev) +{ + struct device *dev = &pdev->dev; + struct rpi_gpiomem_priv *priv = platform_get_drvdata(pdev); + + device_destroy(priv->class, priv->devid); + class_destroy(priv->class); + cdev_del(&priv->rpi_gpiomem_cdev); + unregister_chrdev_region(priv->devid, 1); + kfree(priv); + + dev_info(dev, "%s driver removed - OK", priv->name); + return 0; +} + +static const struct of_device_id rpi_gpiomem_of_match[] = { + { + .compatible = "brcm,bcm2835-gpiomem", + }, + { + .compatible = "raspberrypi,gpiomem", + }, + { /* sentinel */ }, +}; + +MODULE_DEVICE_TABLE(of, rpi_gpiomem_of_match); + +static struct platform_driver rpi_gpiomem_driver = { + .probe = rpi_gpiomem_probe, + .remove = rpi_gpiomem_remove, + .driver = { + .name = DRIVER_NAME, + .owner = THIS_MODULE, + .of_match_table = rpi_gpiomem_of_match, + }, +}; + +module_platform_driver(rpi_gpiomem_driver); + +MODULE_ALIAS("platform:rpi-gpiomem"); +MODULE_LICENSE("Dual BSD/GPL"); +MODULE_DESCRIPTION("Driver for accessing GPIOs from userspace"); +MODULE_AUTHOR("Jonathan Bell ");