gpiolib: cdev: support GPIO_V2_GET_LINE_IOCTL and GPIO_V2_LINE_GET_VALUES_IOCTL

Add support for requesting lines using the GPIO_V2_GET_LINE_IOCTL, and
returning their current values using GPIO_V2_LINE_GET_VALUES_IOCTL.

The struct linereq implementation is based on the v1 struct linehandle
implementation.
Signed-off-by: Kent Gibson <warthog618@gmail.com>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>

drivers/gpio/gpiolib-cdev.c

 // SPDX-License-Identifier: GPL-2.0
 
 #include <linux/anon_inodes.h>
+#include <linux/atomic.h>
 #include <linux/bitmap.h>
+#include <linux/build_bug.h>
 #include <linux/cdev.h>
 #include <linux/compat.h>
 #include <linux/device.h>
@@ -24,6 +26,25 @@
 #include "gpiolib.h"
 #include "gpiolib-cdev.h"
 
+/*
+ * Array sizes must ensure 64-bit alignment and not create holes in the
+ * struct packing.
+ */
+static_assert(IS_ALIGNED(GPIO_V2_LINES_MAX, 2));
+static_assert(IS_ALIGNED(GPIO_MAX_NAME_SIZE, 8));
+
+/*
+ * Check that uAPI structs are 64-bit aligned for 32/64-bit compatibility
+ */
+static_assert(IS_ALIGNED(sizeof(struct gpio_v2_line_attribute), 8));
+static_assert(IS_ALIGNED(sizeof(struct gpio_v2_line_config_attribute), 8));
+static_assert(IS_ALIGNED(sizeof(struct gpio_v2_line_config), 8));
+static_assert(IS_ALIGNED(sizeof(struct gpio_v2_line_request), 8));
+static_assert(IS_ALIGNED(sizeof(struct gpio_v2_line_info), 8));
+static_assert(IS_ALIGNED(sizeof(struct gpio_v2_line_info_changed), 8));
+static_assert(IS_ALIGNED(sizeof(struct gpio_v2_line_event), 8));
+static_assert(IS_ALIGNED(sizeof(struct gpio_v2_line_values), 8));
+
 /* Character device interface to GPIO.
  *
  * The GPIO character device, /dev/gpiochipN, provides userspace an
@@ -34,6 +55,7 @@
  * GPIO line handle management
  */
 
+#ifdef CONFIG_GPIO_CDEV_V1
 /**
  * struct linehandle_state - contains the state of a userspace handle
  * @gdev: the GPIO device the handle pertains to
@@ -376,6 +398,402 @@ static int linehandle_create(struct gpio_device *gdev, void __user *ip)
 	linehandle_free(lh);
 	return ret;
 }
+#endif /* CONFIG_GPIO_CDEV_V1 */
+
+/**
+ * struct line - contains the state of a requested line
+ * @desc: the GPIO descriptor for this line.
+ */
+struct line {
+	struct gpio_desc *desc;
+};
+
+/**
+ * struct linereq - contains the state of a userspace line request
+ * @gdev: the GPIO device the line request pertains to
+ * @label: consumer label used to tag GPIO descriptors
+ * @num_lines: the number of lines in the lines array
+ * @lines: the lines held by this line request, with @num_lines elements.
+ */
+struct linereq {
+	struct gpio_device *gdev;
+	const char *label;
+	u32 num_lines;
+	struct line lines[];
+};
+
+#define GPIO_V2_LINE_BIAS_FLAGS \
+	(GPIO_V2_LINE_FLAG_BIAS_PULL_UP | \
+	 GPIO_V2_LINE_FLAG_BIAS_PULL_DOWN | \
+	 GPIO_V2_LINE_FLAG_BIAS_DISABLED)
+
+#define GPIO_V2_LINE_DIRECTION_FLAGS \
+	(GPIO_V2_LINE_FLAG_INPUT | \
+	 GPIO_V2_LINE_FLAG_OUTPUT)
+
+#define GPIO_V2_LINE_DRIVE_FLAGS \
+	(GPIO_V2_LINE_FLAG_OPEN_DRAIN | \
+	 GPIO_V2_LINE_FLAG_OPEN_SOURCE)
+
+#define GPIO_V2_LINE_VALID_FLAGS \
+	(GPIO_V2_LINE_FLAG_ACTIVE_LOW | \
+	 GPIO_V2_LINE_DIRECTION_FLAGS | \
+	 GPIO_V2_LINE_DRIVE_FLAGS | \
+	 GPIO_V2_LINE_BIAS_FLAGS)
+
+static u64 gpio_v2_line_config_flags(struct gpio_v2_line_config *lc,
+				     unsigned int line_idx)
+{
+	unsigned int i;
+	u64 mask = BIT_ULL(line_idx);
+
+	for (i = 0; i < lc->num_attrs; i++) {
+		if ((lc->attrs[i].attr.id == GPIO_V2_LINE_ATTR_ID_FLAGS) &&
+		    (lc->attrs[i].mask & mask))
+			return lc->attrs[i].attr.flags;
+	}
+	return lc->flags;
+}
+
+static int gpio_v2_line_config_output_value(struct gpio_v2_line_config *lc,
+					    unsigned int line_idx)
+{
+	unsigned int i;
+	u64 mask = BIT_ULL(line_idx);
+
+	for (i = 0; i < lc->num_attrs; i++) {
+		if ((lc->attrs[i].attr.id == GPIO_V2_LINE_ATTR_ID_OUTPUT_VALUES) &&
+		    (lc->attrs[i].mask & mask))
+			return !!(lc->attrs[i].attr.values & mask);
+	}
+	return 0;
+}
+
+static int gpio_v2_line_flags_validate(u64 flags)
+{
+	/* Return an error if an unknown flag is set */
+	if (flags & ~GPIO_V2_LINE_VALID_FLAGS)
+		return -EINVAL;
+
+	/*
+	 * Do not allow both INPUT and OUTPUT flags to be set as they are
+	 * contradictory.
+	 */
+	if ((flags & GPIO_V2_LINE_FLAG_INPUT) &&
+	    (flags & GPIO_V2_LINE_FLAG_OUTPUT))
+		return -EINVAL;
+
+	/*
+	 * Do not allow OPEN_SOURCE and OPEN_DRAIN flags in a single
+	 * request. If the hardware actually supports enabling both at the
+	 * same time the electrical result would be disastrous.
+	 */
+	if ((flags & GPIO_V2_LINE_FLAG_OPEN_DRAIN) &&
+	    (flags & GPIO_V2_LINE_FLAG_OPEN_SOURCE))
+		return -EINVAL;
+
+	/* Drive requires explicit output direction. */
+	if ((flags & GPIO_V2_LINE_DRIVE_FLAGS) &&
+	    !(flags & GPIO_V2_LINE_FLAG_OUTPUT))
+		return -EINVAL;
+
+	/* Bias requires explicit direction. */
+	if ((flags & GPIO_V2_LINE_BIAS_FLAGS) &&
+	    !(flags & GPIO_V2_LINE_DIRECTION_FLAGS))
+		return -EINVAL;
+
+	/* Only one bias flag can be set. */
+	if (((flags & GPIO_V2_LINE_FLAG_BIAS_DISABLED) &&
+	     (flags & (GPIO_V2_LINE_FLAG_BIAS_PULL_DOWN |
+		       GPIO_V2_LINE_FLAG_BIAS_PULL_UP))) ||
+	    ((flags & GPIO_V2_LINE_FLAG_BIAS_PULL_DOWN) &&
+	     (flags & GPIO_V2_LINE_FLAG_BIAS_PULL_UP)))
+		return -EINVAL;
+
+	return 0;
+}
+
+static int gpio_v2_line_config_validate(struct gpio_v2_line_config *lc,
+					unsigned int num_lines)
+{
+	unsigned int i;
+	u64 flags;
+	int ret;
+
+	if (lc->num_attrs > GPIO_V2_LINE_NUM_ATTRS_MAX)
+		return -EINVAL;
+
+	if (memchr_inv(lc->padding, 0, sizeof(lc->padding)))
+		return -EINVAL;
+
+	for (i = 0; i < num_lines; i++) {
+		flags = gpio_v2_line_config_flags(lc, i);
+		ret = gpio_v2_line_flags_validate(flags);
+		if (ret)
+			return ret;
+	}
+	return 0;
+}
+
+static void gpio_v2_line_config_flags_to_desc_flags(u64 flags,
+						    unsigned long *flagsp)
+{
+	assign_bit(FLAG_ACTIVE_LOW, flagsp,
+		   flags & GPIO_V2_LINE_FLAG_ACTIVE_LOW);
+
+	if (flags & GPIO_V2_LINE_FLAG_OUTPUT)
+		set_bit(FLAG_IS_OUT, flagsp);
+	else if (flags & GPIO_V2_LINE_FLAG_INPUT)
+		clear_bit(FLAG_IS_OUT, flagsp);
+
+	assign_bit(FLAG_OPEN_DRAIN, flagsp,
+		   flags & GPIO_V2_LINE_FLAG_OPEN_DRAIN);
+	assign_bit(FLAG_OPEN_SOURCE, flagsp,
+		   flags & GPIO_V2_LINE_FLAG_OPEN_SOURCE);
+
+	assign_bit(FLAG_PULL_UP, flagsp,
+		   flags & GPIO_V2_LINE_FLAG_BIAS_PULL_UP);
+	assign_bit(FLAG_PULL_DOWN, flagsp,
+		   flags & GPIO_V2_LINE_FLAG_BIAS_PULL_DOWN);
+	assign_bit(FLAG_BIAS_DISABLE, flagsp,
+		   flags & GPIO_V2_LINE_FLAG_BIAS_DISABLED);
+}
+
+static long linereq_get_values(struct linereq *lr, void __user *ip)
+{
+	struct gpio_v2_line_values lv;
+	DECLARE_BITMAP(vals, GPIO_V2_LINES_MAX);
+	struct gpio_desc **descs;
+	unsigned int i, didx, num_get;
+	int ret;
+
+	/* NOTE: It's ok to read values of output lines. */
+	if (copy_from_user(&lv, ip, sizeof(lv)))
+		return -EFAULT;
+
+	for (num_get = 0, i = 0; i < lr->num_lines; i++) {
+		if (lv.mask & BIT_ULL(i)) {
+			num_get++;
+			descs = &lr->lines[i].desc;
+		}
+	}
+
+	if (num_get == 0)
+		return -EINVAL;
+
+	if (num_get != 1) {
+		descs = kmalloc_array(num_get, sizeof(*descs), GFP_KERNEL);
+		if (!descs)
+			return -ENOMEM;
+		for (didx = 0, i = 0; i < lr->num_lines; i++) {
+			if (lv.mask & BIT_ULL(i)) {
+				descs[didx] = lr->lines[i].desc;
+				didx++;
+			}
+		}
+	}
+	ret = gpiod_get_array_value_complex(false, true, num_get,
+					    descs, NULL, vals);
+
+	if (num_get != 1)
+		kfree(descs);
+	if (ret)
+		return ret;
+
+	lv.bits = 0;
+	for (didx = 0, i = 0; i < lr->num_lines; i++) {
+		if (lv.mask & BIT_ULL(i)) {
+			if (test_bit(didx, vals))
+				lv.bits |= BIT_ULL(i);
+			didx++;
+		}
+	}
+
+	if (copy_to_user(ip, &lv, sizeof(lv)))
+		return -EFAULT;
+
+	return 0;
+}
+
+static long linereq_ioctl(struct file *file, unsigned int cmd,
+			  unsigned long arg)
+{
+	struct linereq *lr = file->private_data;
+	void __user *ip = (void __user *)arg;
+
+	if (cmd == GPIO_V2_LINE_GET_VALUES_IOCTL)
+		return linereq_get_values(lr, ip);
+
+	return -EINVAL;
+}
+
+#ifdef CONFIG_COMPAT
+static long linereq_ioctl_compat(struct file *file, unsigned int cmd,
+				 unsigned long arg)
+{
+	return linereq_ioctl(file, cmd, (unsigned long)compat_ptr(arg));
+}
+#endif
+
+static void linereq_free(struct linereq *lr)
+{
+	unsigned int i;
+
+	for (i = 0; i < lr->num_lines; i++) {
+		if (lr->lines[i].desc)
+			gpiod_free(lr->lines[i].desc);
+	}
+	kfree(lr->label);
+	put_device(&lr->gdev->dev);
+	kfree(lr);
+}
+
+static int linereq_release(struct inode *inode, struct file *file)
+{
+	struct linereq *lr = file->private_data;
+
+	linereq_free(lr);
+	return 0;
+}
+
+static const struct file_operations line_fileops = {
+	.release = linereq_release,
+	.owner = THIS_MODULE,
+	.llseek = noop_llseek,
+	.unlocked_ioctl = linereq_ioctl,
+#ifdef CONFIG_COMPAT
+	.compat_ioctl = linereq_ioctl_compat,
+#endif
+};
+
+static int linereq_create(struct gpio_device *gdev, void __user *ip)
+{
+	struct gpio_v2_line_request ulr;
+	struct gpio_v2_line_config *lc;
+	struct linereq *lr;
+	struct file *file;
+	u64 flags;
+	unsigned int i;
+	int fd, ret;
+
+	if (copy_from_user(&ulr, ip, sizeof(ulr)))
+		return -EFAULT;
+
+	if ((ulr.num_lines == 0) || (ulr.num_lines > GPIO_V2_LINES_MAX))
+		return -EINVAL;
+
+	if (memchr_inv(ulr.padding, 0, sizeof(ulr.padding)))
+		return -EINVAL;
+
+	lc = &ulr.config;
+	ret = gpio_v2_line_config_validate(lc, ulr.num_lines);
+	if (ret)
+		return ret;
+
+	lr = kzalloc(struct_size(lr, lines, ulr.num_lines), GFP_KERNEL);
+	if (!lr)
+		return -ENOMEM;
+
+	lr->gdev = gdev;
+	get_device(&gdev->dev);
+
+	/* Make sure this is terminated */
+	ulr.consumer[sizeof(ulr.consumer)-1] = '\0';
+	if (strlen(ulr.consumer)) {
+		/* label is only initialized if consumer is set */
+		lr->label = kstrdup(ulr.consumer, GFP_KERNEL);
+		if (!lr->label) {
+			ret = -ENOMEM;
+			goto out_free_linereq;
+		}
+	}
+
+	lr->num_lines = ulr.num_lines;
+
+	/* Request each GPIO */
+	for (i = 0; i < ulr.num_lines; i++) {
+		u32 offset = ulr.offsets[i];
+		struct gpio_desc *desc = gpiochip_get_desc(gdev->chip, offset);
+
+		if (IS_ERR(desc)) {
+			ret = PTR_ERR(desc);
+			goto out_free_linereq;
+		}
+
+		ret = gpiod_request(desc, lr->label);
+		if (ret)
+			goto out_free_linereq;
+
+		lr->lines[i].desc = desc;
+		flags = gpio_v2_line_config_flags(lc, i);
+		gpio_v2_line_config_flags_to_desc_flags(flags, &desc->flags);
+
+		ret = gpiod_set_transitory(desc, false);
+		if (ret < 0)
+			goto out_free_linereq;
+
+		/*
+		 * Lines have to be requested explicitly for input
+		 * or output, else the line will be treated "as is".
+		 */
+		if (flags & GPIO_V2_LINE_FLAG_OUTPUT) {
+			int val = gpio_v2_line_config_output_value(lc, i);
+
+			ret = gpiod_direction_output(desc, val);
+			if (ret)
+				goto out_free_linereq;
+		} else if (flags & GPIO_V2_LINE_FLAG_INPUT) {
+			ret = gpiod_direction_input(desc);
+			if (ret)
+				goto out_free_linereq;
+		}
+
+		blocking_notifier_call_chain(&desc->gdev->notifier,
+					     GPIOLINE_CHANGED_REQUESTED, desc);
+
+		dev_dbg(&gdev->dev, "registered chardev handle for line %d\n",
+			offset);
+	}
+
+	fd = get_unused_fd_flags(O_RDONLY | O_CLOEXEC);
+	if (fd < 0) {
+		ret = fd;
+		goto out_free_linereq;
+	}
+
+	file = anon_inode_getfile("gpio-line", &line_fileops, lr,
+				  O_RDONLY | O_CLOEXEC);
+	if (IS_ERR(file)) {
+		ret = PTR_ERR(file);
+		goto out_put_unused_fd;
+	}
+
+	ulr.fd = fd;
+	if (copy_to_user(ip, &ulr, sizeof(ulr))) {
+		/*
+		 * fput() will trigger the release() callback, so do not go onto
+		 * the regular error cleanup path here.
+		 */
+		fput(file);
+		put_unused_fd(fd);
+		return -EFAULT;
+	}
+
+	fd_install(fd, file);
+
+	dev_dbg(&gdev->dev, "registered chardev handle for %d lines\n",
+		lr->num_lines);
+
+	return 0;
+
+out_put_unused_fd:
+	put_unused_fd(fd);
+out_free_linereq:
+	linereq_free(lr);
+	return ret;
+}
+
+#ifdef CONFIG_GPIO_CDEV_V1
 
 /*
  * GPIO line event management
@@ -745,6 +1163,8 @@ static int lineevent_create(struct gpio_device *gdev, void __user *ip)
 	return ret;
 }
 
+#endif /* CONFIG_GPIO_CDEV_V1 */
+
 static void gpio_desc_to_lineinfo(struct gpio_desc *desc,
 				  struct gpioline_info *info)
 {
@@ -843,6 +1263,7 @@ static long gpio_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 		if (copy_to_user(ip, &chipinfo, sizeof(chipinfo)))
 			return -EFAULT;
 		return 0;
+#ifdef CONFIG_GPIO_CDEV_V1
 	} else if (cmd == GPIO_GET_LINEINFO_IOCTL) {
 		struct gpioline_info lineinfo;
 
@@ -885,6 +1306,9 @@ static long gpio_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 		}
 
 		return 0;
+#endif /* CONFIG_GPIO_CDEV_V1 */
+	} else if (cmd == GPIO_V2_GET_LINE_IOCTL) {
+		return linereq_create(gdev, ip);
 	} else if (cmd == GPIO_GET_LINEINFO_UNWATCH_IOCTL) {
 		if (copy_from_user(&offset, ip, sizeof(offset)))
 			return -EFAULT;