Merge tag 'net-next-6.3' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-nextgrafted

Pull networking updates from Jakub Kicinski:
 "Core:

   - Add dedicated kmem_cache for typical/small skb->head, avoid having
     to access struct page at kfree time, and improve memory use.

   - Introduce sysctl to set default RPS configuration for new netdevs.

   - Define Netlink protocol specification format which can be used to
     describe messages used by each family and auto-generate parsers.
     Add tools for generating kernel data structures and uAPI headers.

   - Expose all net/core sysctls inside netns.

   - Remove 4s sleep in netpoll if carrier is instantly detected on
     boot.

   - Add configurable limit of MDB entries per port, and port-vlan.

   - Continue populating drop reasons throughout the stack.

   - Retire a handful of legacy Qdiscs and classifiers.

  Protocols:

   - Support IPv4 big TCP (TSO frames larger than 64kB).

   - Add IP_LOCAL_PORT_RANGE socket option, to control local port range
     on socket by socket basis.

   - Track and report in procfs number of MPTCP sockets used.

   - Support mixing IPv4 and IPv6 flows in the in-kernel MPTCP path
     manager.

   - IPv6: don't check net.ipv6.route.max_size and rely on garbage
     collection to free memory (similarly to IPv4).

   - Support Penultimate Segment Pop (PSP) flavor in SRv6 (RFC8986).

   - ICMP: add per-rate limit counters.

   - Add support for user scanning requests in ieee802154.

   - Remove static WEP support.

   - Support minimal Wi-Fi 7 Extremely High Throughput (EHT) rate
     reporting.

   - WiFi 7 EHT channel puncturing support (client & AP).

  BPF:

   - Add a rbtree data structure following the "next-gen data structure"
     precedent set by recently added linked list, that is, by using
     kfunc + kptr instead of adding a new BPF map type.

   - Expose XDP hints via kfuncs with initial support for RX hash and
     timestamp metadata.

   - Add BPF_F_NO_TUNNEL_KEY extension to bpf_skb_set_tunnel_key to
     better support decap on GRE tunnel devices not operating in collect
     metadata.

   - Improve x86 JIT's codegen for PROBE_MEM runtime error checks.

   - Remove the need for trace_printk_lock for bpf_trace_printk and
     bpf_trace_vprintk helpers.

   - Extend libbpf's bpf_tracing.h support for tracing arguments of
     kprobes/uprobes and syscall as a special case.

   - Significantly reduce the search time for module symbols by
     livepatch and BPF.

   - Enable cpumasks to be used as kptrs, which is useful for tracing
     programs tracking which tasks end up running on which CPUs in
     different time intervals.

   - Add support for BPF trampoline on s390x and riscv64.

   - Add capability to export the XDP features supported by the NIC.

   - Add __bpf_kfunc tag for marking kernel functions as kfuncs.

   - Add cgroup.memory=nobpf kernel parameter option to disable BPF
     memory accounting for container environments.

  Netfilter:

   - Remove the CLUSTERIP target. It has been marked as obsolete for
     years, and we still have WARN splats wrt races of the out-of-band
     /proc interface installed by this target.

   - Add 'destroy' commands to nf_tables. They are identical to the
     existing 'delete' commands, but do not return an error if the
     referenced object (set, chain, rule...) did not exist.

  Driver API:

   - Improve cpumask_local_spread() locality to help NICs set the right
     IRQ affinity on AMD platforms.

   - Separate C22 and C45 MDIO bus transactions more clearly.

   - Introduce new DCB table to control DSCP rewrite on egress.

   - Support configuration of Physical Layer Collision Avoidance (PLCA)
     Reconciliation Sublayer (RS) (802.3cg-2019). Modern version of
     shared medium Ethernet.

   - Support for MAC Merge layer (IEEE 802.3-2018 clause 99). Allowing
     preemption of low priority frames by high priority frames.

   - Add support for controlling MACSec offload using netlink SET.

   - Rework devlink instance refcounts to allow registration and
     de-registration under the instance lock. Split the code into
     multiple files, drop some of the unnecessarily granular locks and
     factor out common parts of netlink operation handling.

   - Add TX frame aggregation parameters (for USB drivers).

   - Add a new attr TCA_EXT_WARN_MSG to report TC (offload) warning
     messages with notifications for debug.

   - Allow offloading of UDP NEW connections via act_ct.

   - Add support for per action HW stats in TC.

   - Support hardware miss to TC action (continue processing in SW from
     a specific point in the action chain).

   - Warn if old Wireless Extension user space interface is used with
     modern cfg80211/mac80211 drivers. Do not support Wireless
     Extensions for Wi-Fi 7 devices at all. Everyone should switch to
     using nl80211 interface instead.

   - Improve the CAN bit timing configuration. Use extack to return
     error messages directly to user space, update the SJW handling,
     including the definition of a new default value that will benefit
     CAN-FD controllers, by increasing their oscillator tolerance.

  New hardware / drivers:

   - Ethernet:
      - nVidia BlueField-3 support (control traffic driver)
      - Ethernet support for imx93 SoCs
      - Motorcomm yt8531 gigabit Ethernet PHY
      - onsemi NCN26000 10BASE-T1S PHY (with support for PLCA)
      - Microchip LAN8841 PHY (incl. cable diagnostics and PTP)
      - Amlogic gxl MDIO mux

   - WiFi:
      - RealTek RTL8188EU (rtl8xxxu)
      - Qualcomm Wi-Fi 7 devices (ath12k)

   - CAN:
      - Renesas R-Car V4H

  Drivers:

   - Bluetooth:
      - Set Per Platform Antenna Gain (PPAG) for Intel controllers.

   - Ethernet NICs:
      - Intel (1G, igc):
         - support TSN / Qbv / packet scheduling features of i226 model
      - Intel (100G, ice):
         - use GNSS subsystem instead of TTY
         - multi-buffer XDP support
         - extend support for GPIO pins to E823 devices
      - nVidia/Mellanox:
         - update the shared buffer configuration on PFC commands
         - implement PTP adjphase function for HW offset control
         - TC support for Geneve and GRE with VF tunnel offload
         - more efficient crypto key management method
         - multi-port eswitch support
      - Netronome/Corigine:
         - add DCB IEEE support
         - support IPsec offloading for NFP3800
      - Freescale/NXP (enetc):
         - support XDP_REDIRECT for XDP non-linear buffers
         - improve reconfig, avoid link flap and waiting for idle
         - support MAC Merge layer
      - Other NICs:
         - sfc/ef100: add basic devlink support for ef100
         - ionic: rx_push mode operation (writing descriptors via MMIO)
         - bnxt: use the auxiliary bus abstraction for RDMA
         - r8169: disable ASPM and reset bus in case of tx timeout
         - cpsw: support QSGMII mode for J721e CPSW9G
         - cpts: support pulse-per-second output
         - ngbe: add an mdio bus driver
         - usbnet: optimize usbnet_bh() by avoiding unnecessary queuing
         - r8152: handle devices with FW with NCM support
         - amd-xgbe: support 10Mbps, 2.5GbE speeds and rx-adaptation
         - virtio-net: support multi buffer XDP
         - virtio/vsock: replace virtio_vsock_pkt with sk_buff
         - tsnep: XDP support

   - Ethernet high-speed switches:
      - nVidia/Mellanox (mlxsw):
         - add support for latency TLV (in FW control messages)
      - Microchip (sparx5):
         - separate explicit and implicit traffic forwarding rules, make
           the implicit rules always active
         - add support for egress DSCP rewrite
         - IS0 VCAP support (Ingress Classification)
         - IS2 VCAP filters (protos, L3 addrs, L4 ports, flags, ToS
           etc.)
         - ES2 VCAP support (Egress Access Control)
         - support for Per-Stream Filtering and Policing (802.1Q,
           8.6.5.1)

   - Ethernet embedded switches:
      - Marvell (mv88e6xxx):
         - add MAB (port auth) offload support
         - enable PTP receive for mv88e6390
      - NXP (ocelot):
         - support MAC Merge layer
         - support for the the vsc7512 internal copper phys
      - Microchip:
         - lan9303: convert to PHYLINK
         - lan966x: support TC flower filter statistics
         - lan937x: PTP support for KSZ9563/KSZ8563 and LAN937x
         - lan937x: support Credit Based Shaper configuration
         - ksz9477: support Energy Efficient Ethernet
      - other:
         - qca8k: convert to regmap read/write API, use bulk operations
         - rswitch: Improve TX timestamp accuracy

   - Intel WiFi (iwlwifi):
      - EHT (Wi-Fi 7) rate reporting
      - STEP equalizer support: transfer some STEP (connection to radio
        on platforms with integrated wifi) related parameters from the
        BIOS to the firmware.

   - Qualcomm 802.11ax WiFi (ath11k):
      - IPQ5018 support
      - Fine Timing Measurement (FTM) responder role support
      - channel 177 support

   - MediaTek WiFi (mt76):
      - per-PHY LED support
      - mt7996: EHT (Wi-Fi 7) support
      - Wireless Ethernet Dispatch (WED) reset support
      - switch to using page pool allocator

   - RealTek WiFi (rtw89):
      - support new version of Bluetooth co-existance

   - Mobile:
      - rmnet: support TX aggregation"

* tag 'net-next-6.3' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next: (1872 commits)
  page_pool: add a comment explaining the fragment counter usage
  net: ethtool: fix __ethtool_dev_mm_supported() implementation
  ethtool: pse-pd: Fix double word in comments
  xsk: add linux/vmalloc.h to xsk.c
  sefltests: netdevsim: wait for devlink instance after netns removal
  selftest: fib_tests: Always cleanup before exit
  net/mlx5e: Align IPsec ASO result memory to be as required by hardware
  net/mlx5e: TC, Set CT miss to the specific ct action instance
  net/mlx5e: Rename CHAIN_TO_REG to MAPPED_OBJ_TO_REG
  net/mlx5: Refactor tc miss handling to a single function
  net/mlx5: Kconfig: Make tc offload depend on tc skb extension
  net/sched: flower: Support hardware miss to tc action
  net/sched: flower: Move filter handle initialization earlier
  net/sched: cls_api: Support hardware miss to tc action
  net/sched: Rename user cookie and act cookie
  sfc: fix builds without CONFIG_RTC_LIB
  sfc: clean up some inconsistent indentings
  net/mlx4_en: Introduce flexible array to silence overflow warning
  net: lan966x: Fix possible deadlock inside PTP
  net/ulp: Remove redundant ->clone() test in inet_clone_ulp().
  ...

1 files changed, 817 insertions, 0 deletions

diff --git a/drivers/gpio/gpiolib-sysfs.c b/drivers/gpio/gpiolib-sysfs.c
new file mode 100644
index 000000000..cd27bf173
--- /dev/null
+++ b/drivers/gpio/gpiolib-sysfs.c
@@ -0,0 +1,817 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/idr.h>
+#include <linux/mutex.h>
+#include <linux/device.h>
+#include <linux/sysfs.h>
+#include <linux/gpio/consumer.h>
+#include <linux/gpio/driver.h>
+#include <linux/interrupt.h>
+#include <linux/kdev_t.h>
+#include <linux/slab.h>
+#include <linux/ctype.h>
+
+#include "gpiolib.h"
+#include "gpiolib-sysfs.h"
+
+#define GPIO_IRQF_TRIGGER_NONE		0
+#define GPIO_IRQF_TRIGGER_FALLING	BIT(0)
+#define GPIO_IRQF_TRIGGER_RISING	BIT(1)
+#define GPIO_IRQF_TRIGGER_BOTH		(GPIO_IRQF_TRIGGER_FALLING | \
+					 GPIO_IRQF_TRIGGER_RISING)
+
+struct gpiod_data {
+	struct gpio_desc *desc;
+
+	struct mutex mutex;
+	struct kernfs_node *value_kn;
+	int irq;
+	unsigned char irq_flags;
+
+	bool direction_can_change;
+};
+
+/*
+ * Lock to serialise gpiod export and unexport, and prevent re-export of
+ * gpiod whose chip is being unregistered.
+ */
+static DEFINE_MUTEX(sysfs_lock);
+
+/*
+ * /sys/class/gpio/gpioN... only for GPIOs that are exported
+ *   /direction
+ *      * MAY BE OMITTED if kernel won't allow direction changes
+ *      * is read/write as "in" or "out"
+ *      * may also be written as "high" or "low", initializing
+ *        output value as specified ("out" implies "low")
+ *   /value
+ *      * always readable, subject to hardware behavior
+ *      * may be writable, as zero/nonzero
+ *   /edge
+ *      * configures behavior of poll(2) on /value
+ *      * available only if pin can generate IRQs on input
+ *      * is read/write as "none", "falling", "rising", or "both"
+ *   /active_low
+ *      * configures polarity of /value
+ *      * is read/write as zero/nonzero
+ *      * also affects existing and subsequent "falling" and "rising"
+ *        /edge configuration
+ */
+
+static ssize_t direction_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	struct gpiod_data *data = dev_get_drvdata(dev);
+	struct gpio_desc *desc = data->desc;
+	int value;
+
+	mutex_lock(&data->mutex);
+
+	gpiod_get_direction(desc);
+	value = !!test_bit(FLAG_IS_OUT, &desc->flags);
+
+	mutex_unlock(&data->mutex);
+
+	return sysfs_emit(buf, "%s\n", value ? "out" : "in");
+}
+
+static ssize_t direction_store(struct device *dev,
+		struct device_attribute *attr, const char *buf, size_t size)
+{
+	struct gpiod_data *data = dev_get_drvdata(dev);
+	struct gpio_desc *desc = data->desc;
+	ssize_t			status;
+
+	mutex_lock(&data->mutex);
+
+	if (sysfs_streq(buf, "high"))
+		status = gpiod_direction_output_raw(desc, 1);
+	else if (sysfs_streq(buf, "out") || sysfs_streq(buf, "low"))
+		status = gpiod_direction_output_raw(desc, 0);
+	else if (sysfs_streq(buf, "in"))
+		status = gpiod_direction_input(desc);
+	else
+		status = -EINVAL;
+
+	mutex_unlock(&data->mutex);
+
+	return status ? : size;
+}
+static DEVICE_ATTR_RW(direction);
+
+static ssize_t value_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	struct gpiod_data *data = dev_get_drvdata(dev);
+	struct gpio_desc *desc = data->desc;
+	ssize_t			status;
+
+	mutex_lock(&data->mutex);
+
+	status = gpiod_get_value_cansleep(desc);
+
+	mutex_unlock(&data->mutex);
+
+	if (status < 0)
+		return status;
+
+	return sysfs_emit(buf, "%zd\n", status);
+}
+
+static ssize_t value_store(struct device *dev,
+		struct device_attribute *attr, const char *buf, size_t size)
+{
+	struct gpiod_data *data = dev_get_drvdata(dev);
+	struct gpio_desc *desc = data->desc;
+	ssize_t status;
+	long value;
+
+	status = kstrtol(buf, 0, &value);
+
+	mutex_lock(&data->mutex);
+
+	if (!test_bit(FLAG_IS_OUT, &desc->flags)) {
+		status = -EPERM;
+	} else if (status == 0) {
+		gpiod_set_value_cansleep(desc, value);
+		status = size;
+	}
+
+	mutex_unlock(&data->mutex);
+
+	return status;
+}
+static DEVICE_ATTR_PREALLOC(value, S_IWUSR | S_IRUGO, value_show, value_store);
+
+static irqreturn_t gpio_sysfs_irq(int irq, void *priv)
+{
+	struct gpiod_data *data = priv;
+
+	sysfs_notify_dirent(data->value_kn);
+
+	return IRQ_HANDLED;
+}
+
+/* Caller holds gpiod-data mutex. */
+static int gpio_sysfs_request_irq(struct device *dev, unsigned char flags)
+{
+	struct gpiod_data	*data = dev_get_drvdata(dev);
+	struct gpio_desc	*desc = data->desc;
+	unsigned long		irq_flags;
+	int			ret;
+
+	data->irq = gpiod_to_irq(desc);
+	if (data->irq < 0)
+		return -EIO;
+
+	data->value_kn = sysfs_get_dirent(dev->kobj.sd, "value");
+	if (!data->value_kn)
+		return -ENODEV;
+
+	irq_flags = IRQF_SHARED;
+	if (flags & GPIO_IRQF_TRIGGER_FALLING)
+		irq_flags |= test_bit(FLAG_ACTIVE_LOW, &desc->flags) ?
+			IRQF_TRIGGER_RISING : IRQF_TRIGGER_FALLING;
+	if (flags & GPIO_IRQF_TRIGGER_RISING)
+		irq_flags |= test_bit(FLAG_ACTIVE_LOW, &desc->flags) ?
+			IRQF_TRIGGER_FALLING : IRQF_TRIGGER_RISING;
+
+	/*
+	 * FIXME: This should be done in the irq_request_resources callback
+	 *        when the irq is requested, but a few drivers currently fail
+	 *        to do so.
+	 *
+	 *        Remove this redundant call (along with the corresponding
+	 *        unlock) when those drivers have been fixed.
+	 */
+	ret = gpiochip_lock_as_irq(desc->gdev->chip, gpio_chip_hwgpio(desc));
+	if (ret < 0)
+		goto err_put_kn;
+
+	ret = request_any_context_irq(data->irq, gpio_sysfs_irq, irq_flags,
+				"gpiolib", data);
+	if (ret < 0)
+		goto err_unlock;
+
+	data->irq_flags = flags;
+
+	return 0;
+
+err_unlock:
+	gpiochip_unlock_as_irq(desc->gdev->chip, gpio_chip_hwgpio(desc));
+err_put_kn:
+	sysfs_put(data->value_kn);
+
+	return ret;
+}
+
+/*
+ * Caller holds gpiod-data mutex (unless called after class-device
+ * deregistration).
+ */
+static void gpio_sysfs_free_irq(struct device *dev)
+{
+	struct gpiod_data *data = dev_get_drvdata(dev);
+	struct gpio_desc *desc = data->desc;
+
+	data->irq_flags = 0;
+	free_irq(data->irq, data);
+	gpiochip_unlock_as_irq(desc->gdev->chip, gpio_chip_hwgpio(desc));
+	sysfs_put(data->value_kn);
+}
+
+static const char * const trigger_names[] = {
+	[GPIO_IRQF_TRIGGER_NONE]	= "none",
+	[GPIO_IRQF_TRIGGER_FALLING]	= "falling",
+	[GPIO_IRQF_TRIGGER_RISING]	= "rising",
+	[GPIO_IRQF_TRIGGER_BOTH]	= "both",
+};
+
+static ssize_t edge_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	struct gpiod_data *data = dev_get_drvdata(dev);
+	int flags;
+
+	mutex_lock(&data->mutex);
+
+	flags = data->irq_flags;
+
+	mutex_unlock(&data->mutex);
+
+	if (flags >= ARRAY_SIZE(trigger_names))
+		return 0;
+
+	return sysfs_emit(buf, "%s\n", trigger_names[flags]);
+}
+
+static ssize_t edge_store(struct device *dev,
+		struct device_attribute *attr, const char *buf, size_t size)
+{
+	struct gpiod_data *data = dev_get_drvdata(dev);
+	ssize_t	status = size;
+	int flags;
+
+	flags = sysfs_match_string(trigger_names, buf);
+	if (flags < 0)
+		return flags;
+
+	mutex_lock(&data->mutex);
+
+	if (flags == data->irq_flags) {
+		status = size;
+		goto out_unlock;
+	}
+
+	if (data->irq_flags)
+		gpio_sysfs_free_irq(dev);
+
+	if (flags) {
+		status = gpio_sysfs_request_irq(dev, flags);
+		if (!status)
+			status = size;
+	}
+
+out_unlock:
+	mutex_unlock(&data->mutex);
+
+	return status;
+}
+static DEVICE_ATTR_RW(edge);
+
+/* Caller holds gpiod-data mutex. */
+static int gpio_sysfs_set_active_low(struct device *dev, int value)
+{
+	struct gpiod_data	*data = dev_get_drvdata(dev);
+	struct gpio_desc	*desc = data->desc;
+	int			status = 0;
+	unsigned int		flags = data->irq_flags;
+
+	if (!!test_bit(FLAG_ACTIVE_LOW, &desc->flags) == !!value)
+		return 0;
+
+	assign_bit(FLAG_ACTIVE_LOW, &desc->flags, value);
+
+	/* reconfigure poll(2) support if enabled on one edge only */
+	if (flags == GPIO_IRQF_TRIGGER_FALLING ||
+					flags == GPIO_IRQF_TRIGGER_RISING) {
+		gpio_sysfs_free_irq(dev);
+		status = gpio_sysfs_request_irq(dev, flags);
+	}
+
+	return status;
+}
+
+static ssize_t active_low_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	struct gpiod_data *data = dev_get_drvdata(dev);
+	struct gpio_desc *desc = data->desc;
+	int value;
+
+	mutex_lock(&data->mutex);
+
+	value = !!test_bit(FLAG_ACTIVE_LOW, &desc->flags);
+
+	mutex_unlock(&data->mutex);
+
+	return sysfs_emit(buf, "%d\n", value);
+}
+
+static ssize_t active_low_store(struct device *dev,
+		struct device_attribute *attr, const char *buf, size_t size)
+{
+	struct gpiod_data	*data = dev_get_drvdata(dev);
+	ssize_t			status;
+	long			value;
+
+	status = kstrtol(buf, 0, &value);
+	if (status)
+		return status;
+
+	mutex_lock(&data->mutex);
+
+	status = gpio_sysfs_set_active_low(dev, value);
+
+	mutex_unlock(&data->mutex);
+
+	return status ? : size;
+}
+static DEVICE_ATTR_RW(active_low);
+
+static umode_t gpio_is_visible(struct kobject *kobj, struct attribute *attr,
+			       int n)
+{
+	struct device *dev = kobj_to_dev(kobj);
+	struct gpiod_data *data = dev_get_drvdata(dev);
+	struct gpio_desc *desc = data->desc;
+	umode_t mode = attr->mode;
+	bool show_direction = data->direction_can_change;
+
+	if (attr == &dev_attr_direction.attr) {
+		if (!show_direction)
+			mode = 0;
+	} else if (attr == &dev_attr_edge.attr) {
+		if (gpiod_to_irq(desc) < 0)
+			mode = 0;
+		if (!show_direction && test_bit(FLAG_IS_OUT, &desc->flags))
+			mode = 0;
+	}
+
+	return mode;
+}
+
+static struct attribute *gpio_attrs[] = {
+	&dev_attr_direction.attr,
+	&dev_attr_edge.attr,
+	&dev_attr_value.attr,
+	&dev_attr_active_low.attr,
+	NULL,
+};
+
+static const struct attribute_group gpio_group = {
+	.attrs = gpio_attrs,
+	.is_visible = gpio_is_visible,
+};
+
+static const struct attribute_group *gpio_groups[] = {
+	&gpio_group,
+	NULL
+};
+
+/*
+ * /sys/class/gpio/gpiochipN/
+ *   /base ... matching gpio_chip.base (N)
+ *   /label ... matching gpio_chip.label
+ *   /ngpio ... matching gpio_chip.ngpio
+ */
+
+static ssize_t base_show(struct device *dev,
+			       struct device_attribute *attr, char *buf)
+{
+	const struct gpio_chip	*chip = dev_get_drvdata(dev);
+
+	return sysfs_emit(buf, "%d\n", chip->base);
+}
+static DEVICE_ATTR_RO(base);
+
+static ssize_t label_show(struct device *dev,
+			       struct device_attribute *attr, char *buf)
+{
+	const struct gpio_chip	*chip = dev_get_drvdata(dev);
+
+	return sysfs_emit(buf, "%s\n", chip->label ?: "");
+}
+static DEVICE_ATTR_RO(label);
+
+static ssize_t ngpio_show(struct device *dev,
+			       struct device_attribute *attr, char *buf)
+{
+	const struct gpio_chip	*chip = dev_get_drvdata(dev);
+
+	return sysfs_emit(buf, "%u\n", chip->ngpio);
+}
+static DEVICE_ATTR_RO(ngpio);
+
+static struct attribute *gpiochip_attrs[] = {
+	&dev_attr_base.attr,
+	&dev_attr_label.attr,
+	&dev_attr_ngpio.attr,
+	NULL,
+};
+ATTRIBUTE_GROUPS(gpiochip);
+
+/*
+ * /sys/class/gpio/export ... write-only
+ *	integer N ... number of GPIO to export (full access)
+ * /sys/class/gpio/unexport ... write-only
+ *	integer N ... number of GPIO to unexport
+ */
+static ssize_t export_store(struct class *class,
+				struct class_attribute *attr,
+				const char *buf, size_t len)
+{
+	long			gpio;
+	struct gpio_desc	*desc;
+	int			status;
+	struct gpio_chip	*gc;
+	int			offset;
+
+	status = kstrtol(buf, 0, &gpio);
+	if (status < 0)
+		goto done;
+
+	desc = gpio_to_desc(gpio);
+	/* reject invalid GPIOs */
+	if (!desc) {
+		pr_warn("%s: invalid GPIO %ld\n", __func__, gpio);
+		return -EINVAL;
+	}
+	gc = desc->gdev->chip;
+	offset = gpio_chip_hwgpio(desc);
+	if (!gpiochip_line_is_valid(gc, offset)) {
+		pr_warn("%s: GPIO %ld masked\n", __func__, gpio);
+		return -EINVAL;
+	}
+
+	/* No extra locking here; FLAG_SYSFS just signifies that the
+	 * request and export were done by on behalf of userspace, so
+	 * they may be undone on its behalf too.
+	 */
+
+	status = gpiod_request_user(desc, "sysfs");
+	if (status)
+		goto done;
+
+	status = gpiod_set_transitory(desc, false);
+	if (!status) {
+		status = gpiod_export(desc, true);
+		if (status < 0)
+			gpiod_free(desc);
+		else
+			set_bit(FLAG_SYSFS, &desc->flags);
+	}
+
+done:
+	if (status)
+		pr_debug("%s: status %d\n", __func__, status);
+	return status ? : len;
+}
+static CLASS_ATTR_WO(export);
+
+static ssize_t unexport_store(struct class *class,
+				struct class_attribute *attr,
+				const char *buf, size_t len)
+{
+	long			gpio;
+	struct gpio_desc	*desc;
+	int			status;
+
+	status = kstrtol(buf, 0, &gpio);
+	if (status < 0)
+		goto done;
+
+	desc = gpio_to_desc(gpio);
+	/* reject bogus commands (gpio_unexport ignores them) */
+	if (!desc) {
+		pr_warn("%s: invalid GPIO %ld\n", __func__, gpio);
+		return -EINVAL;
+	}
+
+	status = -EINVAL;
+
+	/* No extra locking here; FLAG_SYSFS just signifies that the
+	 * request and export were done by on behalf of userspace, so
+	 * they may be undone on its behalf too.
+	 */
+	if (test_and_clear_bit(FLAG_SYSFS, &desc->flags)) {
+		status = 0;
+		gpiod_free(desc);
+	}
+done:
+	if (status)
+		pr_debug("%s: status %d\n", __func__, status);
+	return status ? : len;
+}
+static CLASS_ATTR_WO(unexport);
+
+static struct attribute *gpio_class_attrs[] = {
+	&class_attr_export.attr,
+	&class_attr_unexport.attr,
+	NULL,
+};
+ATTRIBUTE_GROUPS(gpio_class);
+
+static struct class gpio_class = {
+	.name =		"gpio",
+	.owner =	THIS_MODULE,
+
+	.class_groups = gpio_class_groups,
+};
+
+
+/**
+ * gpiod_export - export a GPIO through sysfs
+ * @desc: GPIO to make available, already requested
+ * @direction_may_change: true if userspace may change GPIO direction
+ * Context: arch_initcall or later
+ *
+ * When drivers want to make a GPIO accessible to userspace after they
+ * have requested it -- perhaps while debugging, or as part of their
+ * public interface -- they may use this routine.  If the GPIO can
+ * change direction (some can't) and the caller allows it, userspace
+ * will see "direction" sysfs attribute which may be used to change
+ * the gpio's direction.  A "value" attribute will always be provided.
+ *
+ * Returns zero on success, else an error.
+ */
+int gpiod_export(struct gpio_desc *desc, bool direction_may_change)
+{
+	struct gpio_chip	*chip;
+	struct gpio_device	*gdev;
+	struct gpiod_data	*data;
+	unsigned long		flags;
+	int			status;
+	const char		*ioname = NULL;
+	struct device		*dev;
+	int			offset;
+
+	/* can't export until sysfs is available ... */
+	if (!gpio_class.p) {
+		pr_debug("%s: called too early!\n", __func__);
+		return -ENOENT;
+	}
+
+	if (!desc) {
+		pr_debug("%s: invalid gpio descriptor\n", __func__);
+		return -EINVAL;
+	}
+
+	gdev = desc->gdev;
+	chip = gdev->chip;
+
+	mutex_lock(&sysfs_lock);
+
+	/* check if chip is being removed */
+	if (!chip || !gdev->mockdev) {
+		status = -ENODEV;
+		goto err_unlock;
+	}
+
+	spin_lock_irqsave(&gpio_lock, flags);
+	if (!test_bit(FLAG_REQUESTED, &desc->flags) ||
+	     test_bit(FLAG_EXPORT, &desc->flags)) {
+		spin_unlock_irqrestore(&gpio_lock, flags);
+		gpiod_dbg(desc, "%s: unavailable (requested=%d, exported=%d)\n",
+				__func__,
+				test_bit(FLAG_REQUESTED, &desc->flags),
+				test_bit(FLAG_EXPORT, &desc->flags));
+		status = -EPERM;
+		goto err_unlock;
+	}
+	spin_unlock_irqrestore(&gpio_lock, flags);
+
+	data = kzalloc(sizeof(*data), GFP_KERNEL);
+	if (!data) {
+		status = -ENOMEM;
+		goto err_unlock;
+	}
+
+	data->desc = desc;
+	mutex_init(&data->mutex);
+	if (chip->direction_input && chip->direction_output)
+		data->direction_can_change = direction_may_change;
+	else
+		data->direction_can_change = false;
+
+	offset = gpio_chip_hwgpio(desc);
+	if (chip->names && chip->names[offset])
+		ioname = chip->names[offset];
+
+	dev = device_create_with_groups(&gpio_class, &gdev->dev,
+					MKDEV(0, 0), data, gpio_groups,
+					ioname ? ioname : "gpio%u",
+					desc_to_gpio(desc));
+	if (IS_ERR(dev)) {
+		status = PTR_ERR(dev);
+		goto err_free_data;
+	}
+
+	set_bit(FLAG_EXPORT, &desc->flags);
+	mutex_unlock(&sysfs_lock);
+	return 0;
+
+err_free_data:
+	kfree(data);
+err_unlock:
+	mutex_unlock(&sysfs_lock);
+	gpiod_dbg(desc, "%s: status %d\n", __func__, status);
+	return status;
+}
+EXPORT_SYMBOL_GPL(gpiod_export);
+
+static int match_export(struct device *dev, const void *desc)
+{
+	struct gpiod_data *data = dev_get_drvdata(dev);
+
+	return data->desc == desc;
+}
+
+/**
+ * gpiod_export_link - create a sysfs link to an exported GPIO node
+ * @dev: device under which to create symlink
+ * @name: name of the symlink
+ * @desc: GPIO to create symlink to, already exported
+ *
+ * Set up a symlink from /sys/.../dev/name to /sys/class/gpio/gpioN
+ * node. Caller is responsible for unlinking.
+ *
+ * Returns zero on success, else an error.
+ */
+int gpiod_export_link(struct device *dev, const char *name,
+		      struct gpio_desc *desc)
+{
+	struct device *cdev;
+	int ret;
+
+	if (!desc) {
+		pr_warn("%s: invalid GPIO\n", __func__);
+		return -EINVAL;
+	}
+
+	cdev = class_find_device(&gpio_class, NULL, desc, match_export);
+	if (!cdev)
+		return -ENODEV;
+
+	ret = sysfs_create_link(&dev->kobj, &cdev->kobj, name);
+	put_device(cdev);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(gpiod_export_link);
+
+/**
+ * gpiod_unexport - reverse effect of gpiod_export()
+ * @desc: GPIO to make unavailable
+ *
+ * This is implicit on gpiod_free().
+ */
+void gpiod_unexport(struct gpio_desc *desc)
+{
+	struct gpiod_data *data;
+	struct device *dev;
+
+	if (!desc) {
+		pr_warn("%s: invalid GPIO\n", __func__);
+		return;
+	}
+
+	mutex_lock(&sysfs_lock);
+
+	if (!test_bit(FLAG_EXPORT, &desc->flags))
+		goto err_unlock;
+
+	dev = class_find_device(&gpio_class, NULL, desc, match_export);
+	if (!dev)
+		goto err_unlock;
+
+	data = dev_get_drvdata(dev);
+
+	clear_bit(FLAG_EXPORT, &desc->flags);
+
+	device_unregister(dev);
+
+	/*
+	 * Release irq after deregistration to prevent race with edge_store.
+	 */
+	if (data->irq_flags)
+		gpio_sysfs_free_irq(dev);
+
+	mutex_unlock(&sysfs_lock);
+
+	put_device(dev);
+	kfree(data);
+
+	return;
+
+err_unlock:
+	mutex_unlock(&sysfs_lock);
+}
+EXPORT_SYMBOL_GPL(gpiod_unexport);
+
+int gpiochip_sysfs_register(struct gpio_device *gdev)
+{
+	struct device	*dev;
+	struct device	*parent;
+	struct gpio_chip *chip = gdev->chip;
+
+	/*
+	 * Many systems add gpio chips for SOC support very early,
+	 * before driver model support is available.  In those cases we
+	 * register later, in gpiolib_sysfs_init() ... here we just
+	 * verify that _some_ field of gpio_class got initialized.
+	 */
+	if (!gpio_class.p)
+		return 0;
+
+	/*
+	 * For sysfs backward compatibility we need to preserve this
+	 * preferred parenting to the gpio_chip parent field, if set.
+	 */
+	if (chip->parent)
+		parent = chip->parent;
+	else
+		parent = &gdev->dev;
+
+	/* use chip->base for the ID; it's already known to be unique */
+	dev = device_create_with_groups(&gpio_class, parent, MKDEV(0, 0), chip,
+					gpiochip_groups, GPIOCHIP_NAME "%d",
+					chip->base);
+	if (IS_ERR(dev))
+		return PTR_ERR(dev);
+
+	mutex_lock(&sysfs_lock);
+	gdev->mockdev = dev;
+	mutex_unlock(&sysfs_lock);
+
+	return 0;
+}
+
+void gpiochip_sysfs_unregister(struct gpio_device *gdev)
+{
+	struct gpio_desc *desc;
+	struct gpio_chip *chip = gdev->chip;
+
+	if (!gdev->mockdev)
+		return;
+
+	device_unregister(gdev->mockdev);
+
+	/* prevent further gpiod exports */
+	mutex_lock(&sysfs_lock);
+	gdev->mockdev = NULL;
+	mutex_unlock(&sysfs_lock);
+
+	/* unregister gpiod class devices owned by sysfs */
+	for_each_gpio_desc_with_flag(chip, desc, FLAG_SYSFS)
+		gpiod_free(desc);
+}
+
+static int __init gpiolib_sysfs_init(void)
+{
+	int		status;
+	unsigned long	flags;
+	struct gpio_device *gdev;
+
+	status = class_register(&gpio_class);
+	if (status < 0)
+		return status;
+
+	/* Scan and register the gpio_chips which registered very
+	 * early (e.g. before the class_register above was called).
+	 *
+	 * We run before arch_initcall() so chip->dev nodes can have
+	 * registered, and so arch_initcall() can always gpio_export().
+	 */
+	spin_lock_irqsave(&gpio_lock, flags);
+	list_for_each_entry(gdev, &gpio_devices, list) {
+		if (gdev->mockdev)
+			continue;
+
+		/*
+		 * TODO we yield gpio_lock here because
+		 * gpiochip_sysfs_register() acquires a mutex. This is unsafe
+		 * and needs to be fixed.
+		 *
+		 * Also it would be nice to use gpiochip_find() here so we
+		 * can keep gpio_chips local to gpiolib.c, but the yield of
+		 * gpio_lock prevents us from doing this.
+		 */
+		spin_unlock_irqrestore(&gpio_lock, flags);
+		status = gpiochip_sysfs_register(gdev);
+		spin_lock_irqsave(&gpio_lock, flags);
+	}
+	spin_unlock_irqrestore(&gpio_lock, flags);
+
+	return status;
+}
+postcore_initcall(gpiolib_sysfs_init);