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, 691 insertions, 0 deletions

diff --git a/drivers/comedi/comedi_buf.c b/drivers/comedi/comedi_buf.c
new file mode 100644
index 000000000..393966c09
--- /dev/null
+++ b/drivers/comedi/comedi_buf.c
@@ -0,0 +1,691 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * comedi_buf.c
+ *
+ * COMEDI - Linux Control and Measurement Device Interface
+ * Copyright (C) 1997-2000 David A. Schleef <ds@schleef.org>
+ * Copyright (C) 2002 Frank Mori Hess <fmhess@users.sourceforge.net>
+ */
+
+#include <linux/vmalloc.h>
+#include <linux/slab.h>
+#include <linux/comedi/comedidev.h>
+#include "comedi_internal.h"
+
+#ifdef PAGE_KERNEL_NOCACHE
+#define COMEDI_PAGE_PROTECTION		PAGE_KERNEL_NOCACHE
+#else
+#define COMEDI_PAGE_PROTECTION		PAGE_KERNEL
+#endif
+
+static void comedi_buf_map_kref_release(struct kref *kref)
+{
+	struct comedi_buf_map *bm =
+		container_of(kref, struct comedi_buf_map, refcount);
+	struct comedi_buf_page *buf;
+	unsigned int i;
+
+	if (bm->page_list) {
+		if (bm->dma_dir != DMA_NONE) {
+			/*
+			 * DMA buffer was allocated as a single block.
+			 * Address is in page_list[0].
+			 */
+			buf = &bm->page_list[0];
+			dma_free_coherent(bm->dma_hw_dev,
+					  PAGE_SIZE * bm->n_pages,
+					  buf->virt_addr, buf->dma_addr);
+		} else {
+			for (i = 0; i < bm->n_pages; i++) {
+				buf = &bm->page_list[i];
+				ClearPageReserved(virt_to_page(buf->virt_addr));
+				free_page((unsigned long)buf->virt_addr);
+			}
+		}
+		vfree(bm->page_list);
+	}
+	if (bm->dma_dir != DMA_NONE)
+		put_device(bm->dma_hw_dev);
+	kfree(bm);
+}
+
+static void __comedi_buf_free(struct comedi_device *dev,
+			      struct comedi_subdevice *s)
+{
+	struct comedi_async *async = s->async;
+	struct comedi_buf_map *bm;
+	unsigned long flags;
+
+	if (async->prealloc_buf) {
+		if (s->async_dma_dir == DMA_NONE)
+			vunmap(async->prealloc_buf);
+		async->prealloc_buf = NULL;
+		async->prealloc_bufsz = 0;
+	}
+
+	spin_lock_irqsave(&s->spin_lock, flags);
+	bm = async->buf_map;
+	async->buf_map = NULL;
+	spin_unlock_irqrestore(&s->spin_lock, flags);
+	comedi_buf_map_put(bm);
+}
+
+static struct comedi_buf_map *
+comedi_buf_map_alloc(struct comedi_device *dev, enum dma_data_direction dma_dir,
+		     unsigned int n_pages)
+{
+	struct comedi_buf_map *bm;
+	struct comedi_buf_page *buf;
+	unsigned int i;
+
+	bm = kzalloc(sizeof(*bm), GFP_KERNEL);
+	if (!bm)
+		return NULL;
+
+	kref_init(&bm->refcount);
+	bm->dma_dir = dma_dir;
+	if (bm->dma_dir != DMA_NONE) {
+		/* Need ref to hardware device to free buffer later. */
+		bm->dma_hw_dev = get_device(dev->hw_dev);
+	}
+
+	bm->page_list = vzalloc(sizeof(*buf) * n_pages);
+	if (!bm->page_list)
+		goto err;
+
+	if (bm->dma_dir != DMA_NONE) {
+		void *virt_addr;
+		dma_addr_t dma_addr;
+
+		/*
+		 * Currently, the DMA buffer needs to be allocated as a
+		 * single block so that it can be mmap()'ed.
+		 */
+		virt_addr = dma_alloc_coherent(bm->dma_hw_dev,
+					       PAGE_SIZE * n_pages, &dma_addr,
+					       GFP_KERNEL);
+		if (!virt_addr)
+			goto err;
+
+		for (i = 0; i < n_pages; i++) {
+			buf = &bm->page_list[i];
+			buf->virt_addr = virt_addr + (i << PAGE_SHIFT);
+			buf->dma_addr = dma_addr + (i << PAGE_SHIFT);
+		}
+
+		bm->n_pages = i;
+	} else {
+		for (i = 0; i < n_pages; i++) {
+			buf = &bm->page_list[i];
+			buf->virt_addr = (void *)get_zeroed_page(GFP_KERNEL);
+			if (!buf->virt_addr)
+				break;
+
+			SetPageReserved(virt_to_page(buf->virt_addr));
+		}
+
+		bm->n_pages = i;
+		if (i < n_pages)
+			goto err;
+	}
+
+	return bm;
+
+err:
+	comedi_buf_map_put(bm);
+	return NULL;
+}
+
+static void __comedi_buf_alloc(struct comedi_device *dev,
+			       struct comedi_subdevice *s,
+			       unsigned int n_pages)
+{
+	struct comedi_async *async = s->async;
+	struct page **pages = NULL;
+	struct comedi_buf_map *bm;
+	struct comedi_buf_page *buf;
+	unsigned long flags;
+	unsigned int i;
+
+	if (!IS_ENABLED(CONFIG_HAS_DMA) && s->async_dma_dir != DMA_NONE) {
+		dev_err(dev->class_dev,
+			"dma buffer allocation not supported\n");
+		return;
+	}
+
+	bm = comedi_buf_map_alloc(dev, s->async_dma_dir, n_pages);
+	if (!bm)
+		return;
+
+	spin_lock_irqsave(&s->spin_lock, flags);
+	async->buf_map = bm;
+	spin_unlock_irqrestore(&s->spin_lock, flags);
+
+	if (bm->dma_dir != DMA_NONE) {
+		/*
+		 * DMA buffer was allocated as a single block.
+		 * Address is in page_list[0].
+		 */
+		buf = &bm->page_list[0];
+		async->prealloc_buf = buf->virt_addr;
+	} else {
+		pages = vmalloc(sizeof(struct page *) * n_pages);
+		if (!pages)
+			return;
+
+		for (i = 0; i < n_pages; i++) {
+			buf = &bm->page_list[i];
+			pages[i] = virt_to_page(buf->virt_addr);
+		}
+
+		/* vmap the pages to prealloc_buf */
+		async->prealloc_buf = vmap(pages, n_pages, VM_MAP,
+					   COMEDI_PAGE_PROTECTION);
+
+		vfree(pages);
+	}
+}
+
+void comedi_buf_map_get(struct comedi_buf_map *bm)
+{
+	if (bm)
+		kref_get(&bm->refcount);
+}
+
+int comedi_buf_map_put(struct comedi_buf_map *bm)
+{
+	if (bm)
+		return kref_put(&bm->refcount, comedi_buf_map_kref_release);
+	return 1;
+}
+
+/* helper for "access" vm operation */
+int comedi_buf_map_access(struct comedi_buf_map *bm, unsigned long offset,
+			  void *buf, int len, int write)
+{
+	unsigned int pgoff = offset_in_page(offset);
+	unsigned long pg = offset >> PAGE_SHIFT;
+	int done = 0;
+
+	while (done < len && pg < bm->n_pages) {
+		int l = min_t(int, len - done, PAGE_SIZE - pgoff);
+		void *b = bm->page_list[pg].virt_addr + pgoff;
+
+		if (write)
+			memcpy(b, buf, l);
+		else
+			memcpy(buf, b, l);
+		buf += l;
+		done += l;
+		pg++;
+		pgoff = 0;
+	}
+	return done;
+}
+
+/* returns s->async->buf_map and increments its kref refcount */
+struct comedi_buf_map *
+comedi_buf_map_from_subdev_get(struct comedi_subdevice *s)
+{
+	struct comedi_async *async = s->async;
+	struct comedi_buf_map *bm = NULL;
+	unsigned long flags;
+
+	if (!async)
+		return NULL;
+
+	spin_lock_irqsave(&s->spin_lock, flags);
+	bm = async->buf_map;
+	/* only want it if buffer pages allocated */
+	if (bm && bm->n_pages)
+		comedi_buf_map_get(bm);
+	else
+		bm = NULL;
+	spin_unlock_irqrestore(&s->spin_lock, flags);
+
+	return bm;
+}
+
+bool comedi_buf_is_mmapped(struct comedi_subdevice *s)
+{
+	struct comedi_buf_map *bm = s->async->buf_map;
+
+	return bm && (kref_read(&bm->refcount) > 1);
+}
+
+int comedi_buf_alloc(struct comedi_device *dev, struct comedi_subdevice *s,
+		     unsigned long new_size)
+{
+	struct comedi_async *async = s->async;
+
+	lockdep_assert_held(&dev->mutex);
+
+	/* Round up new_size to multiple of PAGE_SIZE */
+	new_size = (new_size + PAGE_SIZE - 1) & PAGE_MASK;
+
+	/* if no change is required, do nothing */
+	if (async->prealloc_buf && async->prealloc_bufsz == new_size)
+		return 0;
+
+	/* deallocate old buffer */
+	__comedi_buf_free(dev, s);
+
+	/* allocate new buffer */
+	if (new_size) {
+		unsigned int n_pages = new_size >> PAGE_SHIFT;
+
+		__comedi_buf_alloc(dev, s, n_pages);
+
+		if (!async->prealloc_buf) {
+			/* allocation failed */
+			__comedi_buf_free(dev, s);
+			return -ENOMEM;
+		}
+	}
+	async->prealloc_bufsz = new_size;
+
+	return 0;
+}
+
+void comedi_buf_reset(struct comedi_subdevice *s)
+{
+	struct comedi_async *async = s->async;
+
+	async->buf_write_alloc_count = 0;
+	async->buf_write_count = 0;
+	async->buf_read_alloc_count = 0;
+	async->buf_read_count = 0;
+
+	async->buf_write_ptr = 0;
+	async->buf_read_ptr = 0;
+
+	async->cur_chan = 0;
+	async->scans_done = 0;
+	async->scan_progress = 0;
+	async->munge_chan = 0;
+	async->munge_count = 0;
+	async->munge_ptr = 0;
+
+	async->events = 0;
+}
+
+static unsigned int comedi_buf_write_n_unalloc(struct comedi_subdevice *s)
+{
+	struct comedi_async *async = s->async;
+	unsigned int free_end = async->buf_read_count + async->prealloc_bufsz;
+
+	return free_end - async->buf_write_alloc_count;
+}
+
+unsigned int comedi_buf_write_n_available(struct comedi_subdevice *s)
+{
+	struct comedi_async *async = s->async;
+	unsigned int free_end = async->buf_read_count + async->prealloc_bufsz;
+
+	return free_end - async->buf_write_count;
+}
+
+/**
+ * comedi_buf_write_alloc() - Reserve buffer space for writing
+ * @s: COMEDI subdevice.
+ * @nbytes: Maximum space to reserve in bytes.
+ *
+ * Reserve up to @nbytes bytes of space to be written in the COMEDI acquisition
+ * data buffer associated with the subdevice.  The amount reserved is limited
+ * by the space available.
+ *
+ * Return: The amount of space reserved in bytes.
+ */
+unsigned int comedi_buf_write_alloc(struct comedi_subdevice *s,
+				    unsigned int nbytes)
+{
+	struct comedi_async *async = s->async;
+	unsigned int unalloc = comedi_buf_write_n_unalloc(s);
+
+	if (nbytes > unalloc)
+		nbytes = unalloc;
+
+	async->buf_write_alloc_count += nbytes;
+
+	/*
+	 * ensure the async buffer 'counts' are read and updated
+	 * before we write data to the write-alloc'ed buffer space
+	 */
+	smp_mb();
+
+	return nbytes;
+}
+EXPORT_SYMBOL_GPL(comedi_buf_write_alloc);
+
+/*
+ * munging is applied to data by core as it passes between user
+ * and kernel space
+ */
+static unsigned int comedi_buf_munge(struct comedi_subdevice *s,
+				     unsigned int num_bytes)
+{
+	struct comedi_async *async = s->async;
+	unsigned int count = 0;
+	const unsigned int num_sample_bytes = comedi_bytes_per_sample(s);
+
+	if (!s->munge || (async->cmd.flags & CMDF_RAWDATA)) {
+		async->munge_count += num_bytes;
+		return num_bytes;
+	}
+
+	/* don't munge partial samples */
+	num_bytes -= num_bytes % num_sample_bytes;
+	while (count < num_bytes) {
+		int block_size = num_bytes - count;
+		unsigned int buf_end;
+
+		buf_end = async->prealloc_bufsz - async->munge_ptr;
+		if (block_size > buf_end)
+			block_size = buf_end;
+
+		s->munge(s->device, s,
+			 async->prealloc_buf + async->munge_ptr,
+			 block_size, async->munge_chan);
+
+		/*
+		 * ensure data is munged in buffer before the
+		 * async buffer munge_count is incremented
+		 */
+		smp_wmb();
+
+		async->munge_chan += block_size / num_sample_bytes;
+		async->munge_chan %= async->cmd.chanlist_len;
+		async->munge_count += block_size;
+		async->munge_ptr += block_size;
+		async->munge_ptr %= async->prealloc_bufsz;
+		count += block_size;
+	}
+
+	return count;
+}
+
+unsigned int comedi_buf_write_n_allocated(struct comedi_subdevice *s)
+{
+	struct comedi_async *async = s->async;
+
+	return async->buf_write_alloc_count - async->buf_write_count;
+}
+
+/**
+ * comedi_buf_write_free() - Free buffer space after it is written
+ * @s: COMEDI subdevice.
+ * @nbytes: Maximum space to free in bytes.
+ *
+ * Free up to @nbytes bytes of space previously reserved for writing in the
+ * COMEDI acquisition data buffer associated with the subdevice.  The amount of
+ * space freed is limited to the amount that was reserved.  The freed space is
+ * assumed to have been filled with sample data by the writer.
+ *
+ * If the samples in the freed space need to be "munged", do so here.  The
+ * freed space becomes available for allocation by the reader.
+ *
+ * Return: The amount of space freed in bytes.
+ */
+unsigned int comedi_buf_write_free(struct comedi_subdevice *s,
+				   unsigned int nbytes)
+{
+	struct comedi_async *async = s->async;
+	unsigned int allocated = comedi_buf_write_n_allocated(s);
+
+	if (nbytes > allocated)
+		nbytes = allocated;
+
+	async->buf_write_count += nbytes;
+	async->buf_write_ptr += nbytes;
+	comedi_buf_munge(s, async->buf_write_count - async->munge_count);
+	if (async->buf_write_ptr >= async->prealloc_bufsz)
+		async->buf_write_ptr %= async->prealloc_bufsz;
+
+	return nbytes;
+}
+EXPORT_SYMBOL_GPL(comedi_buf_write_free);
+
+/**
+ * comedi_buf_read_n_available() - Determine amount of readable buffer space
+ * @s: COMEDI subdevice.
+ *
+ * Determine the amount of readable buffer space in the COMEDI acquisition data
+ * buffer associated with the subdevice.  The readable buffer space is that
+ * which has been freed by the writer and "munged" to the sample data format
+ * expected by COMEDI if necessary.
+ *
+ * Return: The amount of readable buffer space.
+ */
+unsigned int comedi_buf_read_n_available(struct comedi_subdevice *s)
+{
+	struct comedi_async *async = s->async;
+	unsigned int num_bytes;
+
+	if (!async)
+		return 0;
+
+	num_bytes = async->munge_count - async->buf_read_count;
+
+	/*
+	 * ensure the async buffer 'counts' are read before we
+	 * attempt to read data from the buffer
+	 */
+	smp_rmb();
+
+	return num_bytes;
+}
+EXPORT_SYMBOL_GPL(comedi_buf_read_n_available);
+
+/**
+ * comedi_buf_read_alloc() - Reserve buffer space for reading
+ * @s: COMEDI subdevice.
+ * @nbytes: Maximum space to reserve in bytes.
+ *
+ * Reserve up to @nbytes bytes of previously written and "munged" buffer space
+ * for reading in the COMEDI acquisition data buffer associated with the
+ * subdevice.  The amount reserved is limited to the space available.  The
+ * reader can read from the reserved space and then free it.  A reader is also
+ * allowed to read from the space before reserving it as long as it determines
+ * the amount of readable data available, but the space needs to be marked as
+ * reserved before it can be freed.
+ *
+ * Return: The amount of space reserved in bytes.
+ */
+unsigned int comedi_buf_read_alloc(struct comedi_subdevice *s,
+				   unsigned int nbytes)
+{
+	struct comedi_async *async = s->async;
+	unsigned int available;
+
+	available = async->munge_count - async->buf_read_alloc_count;
+	if (nbytes > available)
+		nbytes = available;
+
+	async->buf_read_alloc_count += nbytes;
+
+	/*
+	 * ensure the async buffer 'counts' are read before we
+	 * attempt to read data from the read-alloc'ed buffer space
+	 */
+	smp_rmb();
+
+	return nbytes;
+}
+EXPORT_SYMBOL_GPL(comedi_buf_read_alloc);
+
+static unsigned int comedi_buf_read_n_allocated(struct comedi_async *async)
+{
+	return async->buf_read_alloc_count - async->buf_read_count;
+}
+
+/**
+ * comedi_buf_read_free() - Free buffer space after it has been read
+ * @s: COMEDI subdevice.
+ * @nbytes: Maximum space to free in bytes.
+ *
+ * Free up to @nbytes bytes of buffer space previously reserved for reading in
+ * the COMEDI acquisition data buffer associated with the subdevice.  The
+ * amount of space freed is limited to the amount that was reserved.
+ *
+ * The freed space becomes available for allocation by the writer.
+ *
+ * Return: The amount of space freed in bytes.
+ */
+unsigned int comedi_buf_read_free(struct comedi_subdevice *s,
+				  unsigned int nbytes)
+{
+	struct comedi_async *async = s->async;
+	unsigned int allocated;
+
+	/*
+	 * ensure data has been read out of buffer before
+	 * the async read count is incremented
+	 */
+	smp_mb();
+
+	allocated = comedi_buf_read_n_allocated(async);
+	if (nbytes > allocated)
+		nbytes = allocated;
+
+	async->buf_read_count += nbytes;
+	async->buf_read_ptr += nbytes;
+	async->buf_read_ptr %= async->prealloc_bufsz;
+	return nbytes;
+}
+EXPORT_SYMBOL_GPL(comedi_buf_read_free);
+
+static void comedi_buf_memcpy_to(struct comedi_subdevice *s,
+				 const void *data, unsigned int num_bytes)
+{
+	struct comedi_async *async = s->async;
+	unsigned int write_ptr = async->buf_write_ptr;
+
+	while (num_bytes) {
+		unsigned int block_size;
+
+		if (write_ptr + num_bytes > async->prealloc_bufsz)
+			block_size = async->prealloc_bufsz - write_ptr;
+		else
+			block_size = num_bytes;
+
+		memcpy(async->prealloc_buf + write_ptr, data, block_size);
+
+		data += block_size;
+		num_bytes -= block_size;
+
+		write_ptr = 0;
+	}
+}
+
+static void comedi_buf_memcpy_from(struct comedi_subdevice *s,
+				   void *dest, unsigned int nbytes)
+{
+	void *src;
+	struct comedi_async *async = s->async;
+	unsigned int read_ptr = async->buf_read_ptr;
+
+	while (nbytes) {
+		unsigned int block_size;
+
+		src = async->prealloc_buf + read_ptr;
+
+		if (nbytes >= async->prealloc_bufsz - read_ptr)
+			block_size = async->prealloc_bufsz - read_ptr;
+		else
+			block_size = nbytes;
+
+		memcpy(dest, src, block_size);
+		nbytes -= block_size;
+		dest += block_size;
+		read_ptr = 0;
+	}
+}
+
+/**
+ * comedi_buf_write_samples() - Write sample data to COMEDI buffer
+ * @s: COMEDI subdevice.
+ * @data: Pointer to source samples.
+ * @nsamples: Number of samples to write.
+ *
+ * Write up to @nsamples samples to the COMEDI acquisition data buffer
+ * associated with the subdevice, mark it as written and update the
+ * acquisition scan progress.  If there is not enough room for the specified
+ * number of samples, the number of samples written is limited to the number
+ * that will fit and the %COMEDI_CB_OVERFLOW event flag is set to cause the
+ * acquisition to terminate with an overrun error.  Set the %COMEDI_CB_BLOCK
+ * event flag if any samples are written to cause waiting tasks to be woken
+ * when the event flags are processed.
+ *
+ * Return: The amount of data written in bytes.
+ */
+unsigned int comedi_buf_write_samples(struct comedi_subdevice *s,
+				      const void *data, unsigned int nsamples)
+{
+	unsigned int max_samples;
+	unsigned int nbytes;
+
+	/*
+	 * Make sure there is enough room in the buffer for all the samples.
+	 * If not, clamp the nsamples to the number that will fit, flag the
+	 * buffer overrun and add the samples that fit.
+	 */
+	max_samples = comedi_bytes_to_samples(s, comedi_buf_write_n_unalloc(s));
+	if (nsamples > max_samples) {
+		dev_warn(s->device->class_dev, "buffer overrun\n");
+		s->async->events |= COMEDI_CB_OVERFLOW;
+		nsamples = max_samples;
+	}
+
+	if (nsamples == 0)
+		return 0;
+
+	nbytes = comedi_buf_write_alloc(s,
+					comedi_samples_to_bytes(s, nsamples));
+	comedi_buf_memcpy_to(s, data, nbytes);
+	comedi_buf_write_free(s, nbytes);
+	comedi_inc_scan_progress(s, nbytes);
+	s->async->events |= COMEDI_CB_BLOCK;
+
+	return nbytes;
+}
+EXPORT_SYMBOL_GPL(comedi_buf_write_samples);
+
+/**
+ * comedi_buf_read_samples() - Read sample data from COMEDI buffer
+ * @s: COMEDI subdevice.
+ * @data: Pointer to destination.
+ * @nsamples: Maximum number of samples to read.
+ *
+ * Read up to @nsamples samples from the COMEDI acquisition data buffer
+ * associated with the subdevice, mark it as read and update the acquisition
+ * scan progress.  Limit the number of samples read to the number available.
+ * Set the %COMEDI_CB_BLOCK event flag if any samples are read to cause waiting
+ * tasks to be woken when the event flags are processed.
+ *
+ * Return: The amount of data read in bytes.
+ */
+unsigned int comedi_buf_read_samples(struct comedi_subdevice *s,
+				     void *data, unsigned int nsamples)
+{
+	unsigned int max_samples;
+	unsigned int nbytes;
+
+	/* clamp nsamples to the number of full samples available */
+	max_samples = comedi_bytes_to_samples(s,
+					      comedi_buf_read_n_available(s));
+	if (nsamples > max_samples)
+		nsamples = max_samples;
+
+	if (nsamples == 0)
+		return 0;
+
+	nbytes = comedi_buf_read_alloc(s,
+				       comedi_samples_to_bytes(s, nsamples));
+	comedi_buf_memcpy_from(s, data, nbytes);
+	comedi_buf_read_free(s, nbytes);
+	comedi_inc_scan_progress(s, nbytes);
+	s->async->events |= COMEDI_CB_BLOCK;
+
+	return nbytes;
+}
+EXPORT_SYMBOL_GPL(comedi_buf_read_samples);