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, 698 insertions, 0 deletions

diff --git a/drivers/tty/tty_buffer.c b/drivers/tty/tty_buffer.c
new file mode 100644
index 000000000..2df86ed90
--- /dev/null
+++ b/drivers/tty/tty_buffer.c
@@ -0,0 +1,698 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Tty buffer allocation management
+ */
+
+#include <linux/types.h>
+#include <linux/errno.h>
+#include <linux/minmax.h>
+#include <linux/tty.h>
+#include <linux/tty_driver.h>
+#include <linux/tty_flip.h>
+#include <linux/timer.h>
+#include <linux/string.h>
+#include <linux/slab.h>
+#include <linux/sched.h>
+#include <linux/wait.h>
+#include <linux/bitops.h>
+#include <linux/delay.h>
+#include <linux/module.h>
+#include <linux/ratelimit.h>
+#include "tty.h"
+
+#define MIN_TTYB_SIZE	256
+#define TTYB_ALIGN_MASK	0xff
+
+/*
+ * Byte threshold to limit memory consumption for flip buffers.
+ * The actual memory limit is > 2x this amount.
+ */
+#define TTYB_DEFAULT_MEM_LIMIT	(640 * 1024UL)
+
+/*
+ * We default to dicing tty buffer allocations to this many characters
+ * in order to avoid multiple page allocations. We know the size of
+ * tty_buffer itself but it must also be taken into account that the
+ * buffer is 256 byte aligned. See tty_buffer_find for the allocation
+ * logic this must match.
+ */
+
+#define TTY_BUFFER_PAGE	(((PAGE_SIZE - sizeof(struct tty_buffer)) / 2) & ~TTYB_ALIGN_MASK)
+
+/**
+ * tty_buffer_lock_exclusive	-	gain exclusive access to buffer
+ * @port: tty port owning the flip buffer
+ *
+ * Guarantees safe use of the &tty_ldisc_ops.receive_buf() method by excluding
+ * the buffer work and any pending flush from using the flip buffer. Data can
+ * continue to be added concurrently to the flip buffer from the driver side.
+ *
+ * See also tty_buffer_unlock_exclusive().
+ */
+void tty_buffer_lock_exclusive(struct tty_port *port)
+{
+	struct tty_bufhead *buf = &port->buf;
+
+	atomic_inc(&buf->priority);
+	mutex_lock(&buf->lock);
+}
+EXPORT_SYMBOL_GPL(tty_buffer_lock_exclusive);
+
+/**
+ * tty_buffer_unlock_exclusive	-	release exclusive access
+ * @port: tty port owning the flip buffer
+ *
+ * The buffer work is restarted if there is data in the flip buffer.
+ *
+ * See also tty_buffer_lock_exclusive().
+ */
+void tty_buffer_unlock_exclusive(struct tty_port *port)
+{
+	struct tty_bufhead *buf = &port->buf;
+	int restart;
+
+	restart = buf->head->commit != buf->head->read;
+
+	atomic_dec(&buf->priority);
+	mutex_unlock(&buf->lock);
+	if (restart)
+		queue_work(system_unbound_wq, &buf->work);
+}
+EXPORT_SYMBOL_GPL(tty_buffer_unlock_exclusive);
+
+/**
+ * tty_buffer_space_avail	-	return unused buffer space
+ * @port: tty port owning the flip buffer
+ *
+ * Returns: the # of bytes which can be written by the driver without reaching
+ * the buffer limit.
+ *
+ * Note: this does not guarantee that memory is available to write the returned
+ * # of bytes (use tty_prepare_flip_string() to pre-allocate if memory
+ * guarantee is required).
+ */
+unsigned int tty_buffer_space_avail(struct tty_port *port)
+{
+	int space = port->buf.mem_limit - atomic_read(&port->buf.mem_used);
+
+	return max(space, 0);
+}
+EXPORT_SYMBOL_GPL(tty_buffer_space_avail);
+
+static void tty_buffer_reset(struct tty_buffer *p, size_t size)
+{
+	p->used = 0;
+	p->size = size;
+	p->next = NULL;
+	p->commit = 0;
+	p->lookahead = 0;
+	p->read = 0;
+	p->flags = true;
+}
+
+/**
+ * tty_buffer_free_all		-	free buffers used by a tty
+ * @port: tty port to free from
+ *
+ * Remove all the buffers pending on a tty whether queued with data or in the
+ * free ring. Must be called when the tty is no longer in use.
+ */
+void tty_buffer_free_all(struct tty_port *port)
+{
+	struct tty_bufhead *buf = &port->buf;
+	struct tty_buffer *p, *next;
+	struct llist_node *llist;
+	unsigned int freed = 0;
+	int still_used;
+
+	while ((p = buf->head) != NULL) {
+		buf->head = p->next;
+		freed += p->size;
+		if (p->size > 0)
+			kfree(p);
+	}
+	llist = llist_del_all(&buf->free);
+	llist_for_each_entry_safe(p, next, llist, free)
+		kfree(p);
+
+	tty_buffer_reset(&buf->sentinel, 0);
+	buf->head = &buf->sentinel;
+	buf->tail = &buf->sentinel;
+
+	still_used = atomic_xchg(&buf->mem_used, 0);
+	WARN(still_used != freed, "we still have not freed %d bytes!",
+			still_used - freed);
+}
+
+/**
+ * tty_buffer_alloc	-	allocate a tty buffer
+ * @port: tty port
+ * @size: desired size (characters)
+ *
+ * Allocate a new tty buffer to hold the desired number of characters. We
+ * round our buffers off in 256 character chunks to get better allocation
+ * behaviour.
+ *
+ * Returns: %NULL if out of memory or the allocation would exceed the per
+ * device queue.
+ */
+static struct tty_buffer *tty_buffer_alloc(struct tty_port *port, size_t size)
+{
+	struct llist_node *free;
+	struct tty_buffer *p;
+
+	/* Round the buffer size out */
+	size = __ALIGN_MASK(size, TTYB_ALIGN_MASK);
+
+	if (size <= MIN_TTYB_SIZE) {
+		free = llist_del_first(&port->buf.free);
+		if (free) {
+			p = llist_entry(free, struct tty_buffer, free);
+			goto found;
+		}
+	}
+
+	/* Should possibly check if this fails for the largest buffer we
+	 * have queued and recycle that ?
+	 */
+	if (atomic_read(&port->buf.mem_used) > port->buf.mem_limit)
+		return NULL;
+	p = kmalloc(sizeof(struct tty_buffer) + 2 * size,
+		    GFP_ATOMIC | __GFP_NOWARN);
+	if (p == NULL)
+		return NULL;
+
+found:
+	tty_buffer_reset(p, size);
+	atomic_add(size, &port->buf.mem_used);
+	return p;
+}
+
+/**
+ * tty_buffer_free		-	free a tty buffer
+ * @port: tty port owning the buffer
+ * @b: the buffer to free
+ *
+ * Free a tty buffer, or add it to the free list according to our internal
+ * strategy.
+ */
+static void tty_buffer_free(struct tty_port *port, struct tty_buffer *b)
+{
+	struct tty_bufhead *buf = &port->buf;
+
+	/* Dumb strategy for now - should keep some stats */
+	WARN_ON(atomic_sub_return(b->size, &buf->mem_used) < 0);
+
+	if (b->size > MIN_TTYB_SIZE)
+		kfree(b);
+	else if (b->size > 0)
+		llist_add(&b->free, &buf->free);
+}
+
+/**
+ * tty_buffer_flush		-	flush full tty buffers
+ * @tty: tty to flush
+ * @ld: optional ldisc ptr (must be referenced)
+ *
+ * Flush all the buffers containing receive data. If @ld != %NULL, flush the
+ * ldisc input buffer.
+ *
+ * Locking: takes buffer lock to ensure single-threaded flip buffer 'consumer'.
+ */
+void tty_buffer_flush(struct tty_struct *tty, struct tty_ldisc *ld)
+{
+	struct tty_port *port = tty->port;
+	struct tty_bufhead *buf = &port->buf;
+	struct tty_buffer *next;
+
+	atomic_inc(&buf->priority);
+
+	mutex_lock(&buf->lock);
+	/* paired w/ release in __tty_buffer_request_room; ensures there are
+	 * no pending memory accesses to the freed buffer
+	 */
+	while ((next = smp_load_acquire(&buf->head->next)) != NULL) {
+		tty_buffer_free(port, buf->head);
+		buf->head = next;
+	}
+	buf->head->read = buf->head->commit;
+	buf->head->lookahead = buf->head->read;
+
+	if (ld && ld->ops->flush_buffer)
+		ld->ops->flush_buffer(tty);
+
+	atomic_dec(&buf->priority);
+	mutex_unlock(&buf->lock);
+}
+
+/**
+ * __tty_buffer_request_room	-	grow tty buffer if needed
+ * @port: tty port
+ * @size: size desired
+ * @flags: buffer has to store flags along character data
+ *
+ * Make at least @size bytes of linear space available for the tty buffer.
+ *
+ * Will change over to a new buffer if the current buffer is encoded as
+ * %TTY_NORMAL (so has no flags buffer) and the new buffer requires a flags
+ * buffer.
+ *
+ * Returns: the size we managed to find.
+ */
+static int __tty_buffer_request_room(struct tty_port *port, size_t size,
+				     bool flags)
+{
+	struct tty_bufhead *buf = &port->buf;
+	struct tty_buffer *b, *n;
+	int left, change;
+
+	b = buf->tail;
+	if (!b->flags)
+		left = 2 * b->size - b->used;
+	else
+		left = b->size - b->used;
+
+	change = !b->flags && flags;
+	if (change || left < size) {
+		/* This is the slow path - looking for new buffers to use */
+		n = tty_buffer_alloc(port, size);
+		if (n != NULL) {
+			n->flags = flags;
+			buf->tail = n;
+			/*
+			 * Paired w/ acquire in flush_to_ldisc() and lookahead_bufs()
+			 * ensures they see all buffer data.
+			 */
+			smp_store_release(&b->commit, b->used);
+			/*
+			 * Paired w/ acquire in flush_to_ldisc() and lookahead_bufs()
+			 * ensures the latest commit value can be read before the head
+			 * is advanced to the next buffer.
+			 */
+			smp_store_release(&b->next, n);
+		} else if (change)
+			size = 0;
+		else
+			size = left;
+	}
+	return size;
+}
+
+int tty_buffer_request_room(struct tty_port *port, size_t size)
+{
+	return __tty_buffer_request_room(port, size, true);
+}
+EXPORT_SYMBOL_GPL(tty_buffer_request_room);
+
+/**
+ * tty_insert_flip_string_fixed_flag - add characters to the tty buffer
+ * @port: tty port
+ * @chars: characters
+ * @flag: flag value for each character
+ * @size: size
+ *
+ * Queue a series of bytes to the tty buffering. All the characters passed are
+ * marked with the supplied flag.
+ *
+ * Returns: the number added.
+ */
+int tty_insert_flip_string_fixed_flag(struct tty_port *port,
+		const unsigned char *chars, char flag, size_t size)
+{
+	int copied = 0;
+	bool flags = flag != TTY_NORMAL;
+
+	do {
+		int goal = min_t(size_t, size - copied, TTY_BUFFER_PAGE);
+		int space = __tty_buffer_request_room(port, goal, flags);
+		struct tty_buffer *tb = port->buf.tail;
+
+		if (unlikely(space == 0))
+			break;
+		memcpy(char_buf_ptr(tb, tb->used), chars, space);
+		if (tb->flags)
+			memset(flag_buf_ptr(tb, tb->used), flag, space);
+		tb->used += space;
+		copied += space;
+		chars += space;
+		/* There is a small chance that we need to split the data over
+		 * several buffers. If this is the case we must loop.
+		 */
+	} while (unlikely(size > copied));
+	return copied;
+}
+EXPORT_SYMBOL(tty_insert_flip_string_fixed_flag);
+
+/**
+ * tty_insert_flip_string_flags	-	add characters to the tty buffer
+ * @port: tty port
+ * @chars: characters
+ * @flags: flag bytes
+ * @size: size
+ *
+ * Queue a series of bytes to the tty buffering. For each character the flags
+ * array indicates the status of the character.
+ *
+ * Returns: the number added.
+ */
+int tty_insert_flip_string_flags(struct tty_port *port,
+		const unsigned char *chars, const char *flags, size_t size)
+{
+	int copied = 0;
+
+	do {
+		int goal = min_t(size_t, size - copied, TTY_BUFFER_PAGE);
+		int space = tty_buffer_request_room(port, goal);
+		struct tty_buffer *tb = port->buf.tail;
+
+		if (unlikely(space == 0))
+			break;
+		memcpy(char_buf_ptr(tb, tb->used), chars, space);
+		memcpy(flag_buf_ptr(tb, tb->used), flags, space);
+		tb->used += space;
+		copied += space;
+		chars += space;
+		flags += space;
+		/* There is a small chance that we need to split the data over
+		 * several buffers. If this is the case we must loop.
+		 */
+	} while (unlikely(size > copied));
+	return copied;
+}
+EXPORT_SYMBOL(tty_insert_flip_string_flags);
+
+/**
+ * __tty_insert_flip_char   -	add one character to the tty buffer
+ * @port: tty port
+ * @ch: character
+ * @flag: flag byte
+ *
+ * Queue a single byte @ch to the tty buffering, with an optional flag. This is
+ * the slow path of tty_insert_flip_char().
+ */
+int __tty_insert_flip_char(struct tty_port *port, unsigned char ch, char flag)
+{
+	struct tty_buffer *tb;
+	bool flags = flag != TTY_NORMAL;
+
+	if (!__tty_buffer_request_room(port, 1, flags))
+		return 0;
+
+	tb = port->buf.tail;
+	if (tb->flags)
+		*flag_buf_ptr(tb, tb->used) = flag;
+	*char_buf_ptr(tb, tb->used++) = ch;
+
+	return 1;
+}
+EXPORT_SYMBOL(__tty_insert_flip_char);
+
+/**
+ * tty_prepare_flip_string	-	make room for characters
+ * @port: tty port
+ * @chars: return pointer for character write area
+ * @size: desired size
+ *
+ * Prepare a block of space in the buffer for data.
+ *
+ * This is used for drivers that need their own block copy routines into the
+ * buffer. There is no guarantee the buffer is a DMA target!
+ *
+ * Returns: the length available and buffer pointer (@chars) to the space which
+ * is now allocated and accounted for as ready for normal characters.
+ */
+int tty_prepare_flip_string(struct tty_port *port, unsigned char **chars,
+		size_t size)
+{
+	int space = __tty_buffer_request_room(port, size, false);
+
+	if (likely(space)) {
+		struct tty_buffer *tb = port->buf.tail;
+
+		*chars = char_buf_ptr(tb, tb->used);
+		if (tb->flags)
+			memset(flag_buf_ptr(tb, tb->used), TTY_NORMAL, space);
+		tb->used += space;
+	}
+	return space;
+}
+EXPORT_SYMBOL_GPL(tty_prepare_flip_string);
+
+/**
+ * tty_ldisc_receive_buf	-	forward data to line discipline
+ * @ld: line discipline to process input
+ * @p: char buffer
+ * @f: %TTY_NORMAL, %TTY_BREAK, etc. flags buffer
+ * @count: number of bytes to process
+ *
+ * Callers other than flush_to_ldisc() need to exclude the kworker from
+ * concurrent use of the line discipline, see paste_selection().
+ *
+ * Returns: the number of bytes processed.
+ */
+int tty_ldisc_receive_buf(struct tty_ldisc *ld, const unsigned char *p,
+			  const char *f, int count)
+{
+	if (ld->ops->receive_buf2)
+		count = ld->ops->receive_buf2(ld->tty, p, f, count);
+	else {
+		count = min_t(int, count, ld->tty->receive_room);
+		if (count && ld->ops->receive_buf)
+			ld->ops->receive_buf(ld->tty, p, f, count);
+	}
+	return count;
+}
+EXPORT_SYMBOL_GPL(tty_ldisc_receive_buf);
+
+static void lookahead_bufs(struct tty_port *port, struct tty_buffer *head)
+{
+	head->lookahead = max(head->lookahead, head->read);
+
+	while (head) {
+		struct tty_buffer *next;
+		unsigned int count;
+
+		/*
+		 * Paired w/ release in __tty_buffer_request_room();
+		 * ensures commit value read is not stale if the head
+		 * is advancing to the next buffer.
+		 */
+		next = smp_load_acquire(&head->next);
+		/*
+		 * Paired w/ release in __tty_buffer_request_room() or in
+		 * tty_buffer_flush(); ensures we see the committed buffer data.
+		 */
+		count = smp_load_acquire(&head->commit) - head->lookahead;
+		if (!count) {
+			head = next;
+			continue;
+		}
+
+		if (port->client_ops->lookahead_buf) {
+			unsigned char *p, *f = NULL;
+
+			p = char_buf_ptr(head, head->lookahead);
+			if (head->flags)
+				f = flag_buf_ptr(head, head->lookahead);
+
+			port->client_ops->lookahead_buf(port, p, f, count);
+		}
+
+		head->lookahead += count;
+	}
+}
+
+static int
+receive_buf(struct tty_port *port, struct tty_buffer *head, int count)
+{
+	unsigned char *p = char_buf_ptr(head, head->read);
+	const char *f = NULL;
+	int n;
+
+	if (head->flags)
+		f = flag_buf_ptr(head, head->read);
+
+	n = port->client_ops->receive_buf(port, p, f, count);
+	if (n > 0)
+		memset(p, 0, n);
+	return n;
+}
+
+/**
+ * flush_to_ldisc		-	flush data from buffer to ldisc
+ * @work: tty structure passed from work queue.
+ *
+ * This routine is called out of the software interrupt to flush data from the
+ * buffer chain to the line discipline.
+ *
+ * The receive_buf() method is single threaded for each tty instance.
+ *
+ * Locking: takes buffer lock to ensure single-threaded flip buffer 'consumer'.
+ */
+static void flush_to_ldisc(struct work_struct *work)
+{
+	struct tty_port *port = container_of(work, struct tty_port, buf.work);
+	struct tty_bufhead *buf = &port->buf;
+
+	mutex_lock(&buf->lock);
+
+	while (1) {
+		struct tty_buffer *head = buf->head;
+		struct tty_buffer *next;
+		int count, rcvd;
+
+		/* Ldisc or user is trying to gain exclusive access */
+		if (atomic_read(&buf->priority))
+			break;
+
+		/* paired w/ release in __tty_buffer_request_room();
+		 * ensures commit value read is not stale if the head
+		 * is advancing to the next buffer
+		 */
+		next = smp_load_acquire(&head->next);
+		/* paired w/ release in __tty_buffer_request_room() or in
+		 * tty_buffer_flush(); ensures we see the committed buffer data
+		 */
+		count = smp_load_acquire(&head->commit) - head->read;
+		if (!count) {
+			if (next == NULL)
+				break;
+			buf->head = next;
+			tty_buffer_free(port, head);
+			continue;
+		}
+
+		rcvd = receive_buf(port, head, count);
+		head->read += rcvd;
+		if (rcvd < count)
+			lookahead_bufs(port, head);
+		if (!rcvd)
+			break;
+
+		if (need_resched())
+			cond_resched();
+	}
+
+	mutex_unlock(&buf->lock);
+
+}
+
+static inline void tty_flip_buffer_commit(struct tty_buffer *tail)
+{
+	/*
+	 * Paired w/ acquire in flush_to_ldisc(); ensures flush_to_ldisc() sees
+	 * buffer data.
+	 */
+	smp_store_release(&tail->commit, tail->used);
+}
+
+/**
+ * tty_flip_buffer_push		-	push terminal buffers
+ * @port: tty port to push
+ *
+ * Queue a push of the terminal flip buffers to the line discipline. Can be
+ * called from IRQ/atomic context.
+ *
+ * In the event of the queue being busy for flipping the work will be held off
+ * and retried later.
+ */
+void tty_flip_buffer_push(struct tty_port *port)
+{
+	struct tty_bufhead *buf = &port->buf;
+
+	tty_flip_buffer_commit(buf->tail);
+	queue_work(system_unbound_wq, &buf->work);
+}
+EXPORT_SYMBOL(tty_flip_buffer_push);
+
+/**
+ * tty_insert_flip_string_and_push_buffer - add characters to the tty buffer and
+ *	push
+ * @port: tty port
+ * @chars: characters
+ * @size: size
+ *
+ * The function combines tty_insert_flip_string() and tty_flip_buffer_push()
+ * with the exception of properly holding the @port->lock.
+ *
+ * To be used only internally (by pty currently).
+ *
+ * Returns: the number added.
+ */
+int tty_insert_flip_string_and_push_buffer(struct tty_port *port,
+		const unsigned char *chars, size_t size)
+{
+	struct tty_bufhead *buf = &port->buf;
+	unsigned long flags;
+
+	spin_lock_irqsave(&port->lock, flags);
+	size = tty_insert_flip_string(port, chars, size);
+	if (size)
+		tty_flip_buffer_commit(buf->tail);
+	spin_unlock_irqrestore(&port->lock, flags);
+
+	queue_work(system_unbound_wq, &buf->work);
+
+	return size;
+}
+
+/**
+ * tty_buffer_init		-	prepare a tty buffer structure
+ * @port: tty port to initialise
+ *
+ * Set up the initial state of the buffer management for a tty device. Must be
+ * called before the other tty buffer functions are used.
+ */
+void tty_buffer_init(struct tty_port *port)
+{
+	struct tty_bufhead *buf = &port->buf;
+
+	mutex_init(&buf->lock);
+	tty_buffer_reset(&buf->sentinel, 0);
+	buf->head = &buf->sentinel;
+	buf->tail = &buf->sentinel;
+	init_llist_head(&buf->free);
+	atomic_set(&buf->mem_used, 0);
+	atomic_set(&buf->priority, 0);
+	INIT_WORK(&buf->work, flush_to_ldisc);
+	buf->mem_limit = TTYB_DEFAULT_MEM_LIMIT;
+}
+
+/**
+ * tty_buffer_set_limit		-	change the tty buffer memory limit
+ * @port: tty port to change
+ * @limit: memory limit to set
+ *
+ * Change the tty buffer memory limit.
+ *
+ * Must be called before the other tty buffer functions are used.
+ */
+int tty_buffer_set_limit(struct tty_port *port, int limit)
+{
+	if (limit < MIN_TTYB_SIZE)
+		return -EINVAL;
+	port->buf.mem_limit = limit;
+	return 0;
+}
+EXPORT_SYMBOL_GPL(tty_buffer_set_limit);
+
+/* slave ptys can claim nested buffer lock when handling BRK and INTR */
+void tty_buffer_set_lock_subclass(struct tty_port *port)
+{
+	lockdep_set_subclass(&port->buf.lock, TTY_LOCK_SLAVE);
+}
+
+bool tty_buffer_restart_work(struct tty_port *port)
+{
+	return queue_work(system_unbound_wq, &port->buf.work);
+}
+
+bool tty_buffer_cancel_work(struct tty_port *port)
+{
+	return cancel_work_sync(&port->buf.work);
+}
+
+void tty_buffer_flush_work(struct tty_port *port)
+{
+	flush_work(&port->buf.work);
+}