23 files changed, 302 insertions, 141 deletions

diff --git a/MAINTAINERS b/MAINTAINERS
index 05db8b2df438..fdc7368de809 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -4432,6 +4432,7 @@ F:	arch/*/lib/bitops.c
 F:	include/asm-generic/bitops
 F:	include/asm-generic/bitops.h
 F:	include/linux/bitops.h
+F:	lib/hweight.c
 F:	lib/test_bitops.c
 F:	tools/*/bitops*
 
diff --git a/arch/x86/include/asm/cpumask.h b/arch/x86/include/asm/cpumask.h
index 70f6b60ad67b..9df9e9cde670 100644
--- a/arch/x86/include/asm/cpumask.h
+++ b/arch/x86/include/asm/cpumask.h
@@ -2,6 +2,8 @@
 #ifndef _ASM_X86_CPUMASK_H
 #define _ASM_X86_CPUMASK_H
 #ifndef __ASSEMBLER__
+
+#include <linux/compiler.h>
 #include <linux/cpumask.h>
 
 extern void setup_cpu_local_masks(void);
diff --git a/drivers/android/binder/process.rs b/drivers/android/binder/process.rs
index e5237e9ec552..ac981614544e 100644
--- a/drivers/android/binder/process.rs
+++ b/drivers/android/binder/process.rs
@@ -19,6 +19,7 @@ use kernel::{
     cred::Credential,
     error::Error,
     fs::file::{self, File},
+    id_pool::IdPool,
     list::{List, ListArc, ListArcField, ListLinks},
     mm,
     prelude::*,
@@ -394,6 +395,8 @@ kernel::list::impl_list_item! {
 struct ProcessNodeRefs {
     /// Used to look up nodes using the 32-bit id that this process knows it by.
     by_handle: RBTree<u32, ListArc<NodeRefInfo, { NodeRefInfo::LIST_PROC }>>,
+    /// Used to quickly find unused ids in `by_handle`.
+    handle_is_present: IdPool,
     /// Used to look up nodes without knowing their local 32-bit id. The usize is the address of
     /// the underlying `Node` struct as returned by `Node::global_id`.
     by_node: RBTree<usize, u32>,
@@ -408,6 +411,7 @@ impl ProcessNodeRefs {
     fn new() -> Self {
         Self {
             by_handle: RBTree::new(),
+            handle_is_present: IdPool::new(),
             by_node: RBTree::new(),
             freeze_listeners: RBTree::new(),
         }
@@ -802,7 +806,7 @@ impl Process {
     pub(crate) fn insert_or_update_handle(
         self: ArcBorrow<'_, Process>,
         node_ref: NodeRef,
-        is_mananger: bool,
+        is_manager: bool,
     ) -> Result<u32> {
         {
             let mut refs = self.node_refs.lock();
@@ -821,7 +825,33 @@ impl Process {
         let reserve2 = RBTreeNodeReservation::new(GFP_KERNEL)?;
         let info = UniqueArc::new_uninit(GFP_KERNEL)?;
 
-        let mut refs = self.node_refs.lock();
+        let mut refs_lock = self.node_refs.lock();
+        let mut refs = &mut *refs_lock;
+
+        let (unused_id, by_handle_slot) = loop {
+            // ID 0 may only be used by the manager.
+            let start = if is_manager { 0 } else { 1 };
+
+            if let Some(res) = refs.handle_is_present.find_unused_id(start) {
+                match refs.by_handle.entry(res.as_u32()) {
+                    rbtree::Entry::Vacant(entry) => break (res, entry),
+                    rbtree::Entry::Occupied(_) => {
+                        pr_err!("Detected mismatch between handle_is_present and by_handle");
+                        res.acquire();
+                        kernel::warn_on!(true);
+                        return Err(EINVAL);
+                    }
+                }
+            }
+
+            let grow_request = refs.handle_is_present.grow_request().ok_or(ENOMEM)?;
+            drop(refs_lock);
+            let resizer = grow_request.realloc(GFP_KERNEL)?;
+            refs_lock = self.node_refs.lock();
+            refs = &mut *refs_lock;
+            refs.handle_is_present.grow(resizer);
+        };
+        let handle = unused_id.as_u32();
 
         // Do a lookup again as node may have been inserted before the lock was reacquired.
         if let Some(handle_ref) = refs.by_node.get(&node_ref.node.global_id()) {
@@ -831,20 +861,9 @@ impl Process {
             return Ok(handle);
         }
 
-        // Find id.
-        let mut target: u32 = if is_mananger { 0 } else { 1 };
-        for handle in refs.by_handle.keys() {
-            if *handle > target {
-                break;
-            }
-            if *handle == target {
-                target = target.checked_add(1).ok_or(ENOMEM)?;
-            }
-        }
-
         let gid = node_ref.node.global_id();
         let (info_proc, info_node) = {
-            let info_init = NodeRefInfo::new(node_ref, target, self.into());
+            let info_init = NodeRefInfo::new(node_ref, handle, self.into());
             match info.pin_init_with(info_init) {
                 Ok(info) => ListArc::pair_from_pin_unique(info),
                 // error is infallible
@@ -865,9 +884,10 @@ impl Process {
         // `info_node` into the right node's `refs` list.
         unsafe { info_proc.node_ref2().node.insert_node_info(info_node) };
 
-        refs.by_node.insert(reserve1.into_node(gid, target));
-        refs.by_handle.insert(reserve2.into_node(target, info_proc));
-        Ok(target)
+        refs.by_node.insert(reserve1.into_node(gid, handle));
+        by_handle_slot.insert(info_proc, reserve2);
+        unused_id.acquire();
+        Ok(handle)
     }
 
     pub(crate) fn get_transaction_node(&self, handle: u32) -> BinderResult<NodeRef> {
@@ -932,6 +952,16 @@ impl Process {
                 let id = info.node_ref().node.global_id();
                 refs.by_handle.remove(&handle);
                 refs.by_node.remove(&id);
+                refs.handle_is_present.release_id(handle as usize);
+
+                if let Some(shrink) = refs.handle_is_present.shrink_request() {
+                    drop(refs);
+                    // This intentionally ignores allocation failures.
+                    if let Ok(new_bitmap) = shrink.realloc(GFP_KERNEL) {
+                        refs = self.node_refs.lock();
+                        refs.handle_is_present.shrink(new_bitmap);
+                    }
+                }
             }
         } else {
             // All refs are cleared in process exit, so this warning is expected in that case.
diff --git a/drivers/clk/at91/clk-peripheral.c b/drivers/clk/at91/clk-peripheral.c
index e700f40fd87f..e7208c47268b 100644
--- a/drivers/clk/at91/clk-peripheral.c
+++ b/drivers/clk/at91/clk-peripheral.c
@@ -3,6 +3,7 @@
  *  Copyright (C) 2013 Boris BREZILLON <b.brezillon@overkiz.com>
  */
 
+#include <linux/bitfield.h>
 #include <linux/bitops.h>
 #include <linux/clk-provider.h>
 #include <linux/clkdev.h>
diff --git a/drivers/clk/at91/pmc.h b/drivers/clk/at91/pmc.h
index 5daa32c4cf25..543d7aee8d24 100644
--- a/drivers/clk/at91/pmc.h
+++ b/drivers/clk/at91/pmc.h
@@ -117,9 +117,6 @@ struct at91_clk_pms {
 	unsigned int parent;
 };
 
-#define field_get(_mask, _reg) (((_reg) & (_mask)) >> (ffs(_mask) - 1))
-#define field_prep(_mask, _val) (((_val) << (ffs(_mask) - 1)) & (_mask))
-
 #define ndck(a, s) (a[s - 1].id + 1)
 #define nck(a) (a[ARRAY_SIZE(a) - 1].id + 1)
 
diff --git a/drivers/clk/renesas/clk-div6.c b/drivers/clk/renesas/clk-div6.c
index 3abd6e5400ad..f7b827b5e9b2 100644
--- a/drivers/clk/renesas/clk-div6.c
+++ b/drivers/clk/renesas/clk-div6.c
@@ -7,6 +7,7 @@
  * Contact: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
  */
 
+#include <linux/bitfield.h>
 #include <linux/clk-provider.h>
 #include <linux/init.h>
 #include <linux/io.h>
@@ -171,8 +172,7 @@ static u8 cpg_div6_clock_get_parent(struct clk_hw *hw)
 	if (clock->src_mask == 0)
 		return 0;
 
-	hw_index = (readl(clock->reg) & clock->src_mask) >>
-		   __ffs(clock->src_mask);
+	hw_index = field_get(clock->src_mask, readl(clock->reg));
 	for (i = 0; i < clk_hw_get_num_parents(hw); i++) {
 		if (clock->parents[i] == hw_index)
 			return i;
@@ -191,7 +191,7 @@ static int cpg_div6_clock_set_parent(struct clk_hw *hw, u8 index)
 	if (index >= clk_hw_get_num_parents(hw))
 		return -EINVAL;
 
-	src = clock->parents[index] << __ffs(clock->src_mask);
+	src = field_prep(clock->src_mask, clock->parents[index]);
 	writel((readl(clock->reg) & ~clock->src_mask) | src, clock->reg);
 	return 0;
 }
diff --git a/drivers/clk/renesas/rcar-gen3-cpg.c b/drivers/clk/renesas/rcar-gen3-cpg.c
index 10ae20489df9..b954278ddd9d 100644
--- a/drivers/clk/renesas/rcar-gen3-cpg.c
+++ b/drivers/clk/renesas/rcar-gen3-cpg.c
@@ -54,10 +54,8 @@ static unsigned long cpg_pll_clk_recalc_rate(struct clk_hw *hw,
 {
 	struct cpg_pll_clk *pll_clk = to_pll_clk(hw);
 	unsigned int mult;
-	u32 val;
 
-	val = readl(pll_clk->pllcr_reg) & CPG_PLLnCR_STC_MASK;
-	mult = (val >> __ffs(CPG_PLLnCR_STC_MASK)) + 1;
+	mult = FIELD_GET(CPG_PLLnCR_STC_MASK, readl(pll_clk->pllcr_reg)) + 1;
 
 	return parent_rate * mult * pll_clk->fixed_mult;
 }
@@ -94,7 +92,7 @@ static int cpg_pll_clk_set_rate(struct clk_hw *hw, unsigned long rate,
 
 	val = readl(pll_clk->pllcr_reg);
 	val &= ~CPG_PLLnCR_STC_MASK;
-	val |= (mult - 1) << __ffs(CPG_PLLnCR_STC_MASK);
+	val |= FIELD_PREP(CPG_PLLnCR_STC_MASK, mult - 1);
 	writel(val, pll_clk->pllcr_reg);
 
 	for (i = 1000; i; i--) {
@@ -176,11 +174,7 @@ static unsigned long cpg_z_clk_recalc_rate(struct clk_hw *hw,
 					   unsigned long parent_rate)
 {
 	struct cpg_z_clk *zclk = to_z_clk(hw);
-	unsigned int mult;
-	u32 val;
-
-	val = readl(zclk->reg) & zclk->mask;
-	mult = 32 - (val >> __ffs(zclk->mask));
+	unsigned int mult = 32 - field_get(zclk->mask, readl(zclk->reg));
 
 	return DIV_ROUND_CLOSEST_ULL((u64)parent_rate * mult,
 				     32 * zclk->fixed_div);
@@ -231,7 +225,8 @@ static int cpg_z_clk_set_rate(struct clk_hw *hw, unsigned long rate,
 	if (readl(zclk->kick_reg) & CPG_FRQCRB_KICK)
 		return -EBUSY;
 
-	cpg_reg_modify(zclk->reg, zclk->mask, (32 - mult) << __ffs(zclk->mask));
+	cpg_reg_modify(zclk->reg, zclk->mask,
+		       field_prep(zclk->mask, 32 - mult));
 
 	/*
 	 * Set KICK bit in FRQCRB to update hardware setting and wait for
diff --git a/drivers/clk/renesas/rcar-gen4-cpg.c b/drivers/clk/renesas/rcar-gen4-cpg.c
index fb9a876aaba5..db3a0b8ef2b9 100644
--- a/drivers/clk/renesas/rcar-gen4-cpg.c
+++ b/drivers/clk/renesas/rcar-gen4-cpg.c
@@ -279,11 +279,7 @@ static unsigned long cpg_z_clk_recalc_rate(struct clk_hw *hw,
 					   unsigned long parent_rate)
 {
 	struct cpg_z_clk *zclk = to_z_clk(hw);
-	unsigned int mult;
-	u32 val;
-
-	val = readl(zclk->reg) & zclk->mask;
-	mult = 32 - (val >> __ffs(zclk->mask));
+	unsigned int mult = 32 - field_get(zclk->mask, readl(zclk->reg));
 
 	return DIV_ROUND_CLOSEST_ULL((u64)parent_rate * mult,
 				     32 * zclk->fixed_div);
@@ -334,7 +330,8 @@ static int cpg_z_clk_set_rate(struct clk_hw *hw, unsigned long rate,
 	if (readl(zclk->kick_reg) & CPG_FRQCRB_KICK)
 		return -EBUSY;
 
-	cpg_reg_modify(zclk->reg, zclk->mask, (32 - mult) << __ffs(zclk->mask));
+	cpg_reg_modify(zclk->reg, zclk->mask,
+		       field_prep(zclk->mask, 32 - mult));
 
 	/*
 	 * Set KICK bit in FRQCRB to update hardware setting and wait for
diff --git a/drivers/crypto/intel/qat/qat_common/adf_pm_dbgfs_utils.c b/drivers/crypto/intel/qat/qat_common/adf_pm_dbgfs_utils.c
index 69295a9ddf0a..4ccc94ed9493 100644
--- a/drivers/crypto/intel/qat/qat_common/adf_pm_dbgfs_utils.c
+++ b/drivers/crypto/intel/qat/qat_common/adf_pm_dbgfs_utils.c
@@ -1,18 +1,12 @@
 // SPDX-License-Identifier: GPL-2.0-only
 /* Copyright(c) 2025 Intel Corporation */
+#include <linux/bitfield.h>
 #include <linux/bitops.h>
 #include <linux/sprintf.h>
 #include <linux/string_helpers.h>
 
 #include "adf_pm_dbgfs_utils.h"
 
-/*
- * This is needed because a variable is used to index the mask at
- * pm_scnprint_table(), making it not compile time constant, so the compile
- * asserts from FIELD_GET() or u32_get_bits() won't be fulfilled.
- */
-#define field_get(_mask, _reg) (((_reg) & (_mask)) >> (ffs(_mask) - 1))
-
 #define PM_INFO_MAX_KEY_LEN	21
 
 static int pm_scnprint_table(char *buff, const struct pm_status_row *table,
diff --git a/drivers/edac/ie31200_edac.c b/drivers/edac/ie31200_edac.c
index 8d4ddaa85ae8..eaab6af143e1 100644
--- a/drivers/edac/ie31200_edac.c
+++ b/drivers/edac/ie31200_edac.c
@@ -44,6 +44,7 @@
  * but lo_hi_readq() ensures that we are safe across all e3-1200 processors.
  */
 
+#include <linux/bitfield.h>
 #include <linux/module.h>
 #include <linux/init.h>
 #include <linux/pci.h>
@@ -139,9 +140,6 @@
 #define IE31200_CAPID0_DDPCD		BIT(6)
 #define IE31200_CAPID0_ECC		BIT(1)
 
-/* Non-constant mask variant of FIELD_GET() */
-#define field_get(_mask, _reg)  (((_reg) & (_mask)) >> (ffs(_mask) - 1))
-
 static int nr_channels;
 static struct pci_dev *mci_pdev;
 static int ie31200_registered = 1;
diff --git a/drivers/gpio/gpio-aspeed.c b/drivers/gpio/gpio-aspeed.c
index 2e0ae953dd99..cbdf781994dc 100644
--- a/drivers/gpio/gpio-aspeed.c
+++ b/drivers/gpio/gpio-aspeed.c
@@ -5,6 +5,7 @@
  * Joel Stanley <joel@jms.id.au>
  */
 
+#include <linux/bitfield.h>
 #include <linux/cleanup.h>
 #include <linux/clk.h>
 #include <linux/gpio/aspeed.h>
@@ -30,10 +31,6 @@
  */
 #include <linux/gpio/consumer.h>
 
-/* Non-constant mask variant of FIELD_GET() and FIELD_PREP() */
-#define field_get(_mask, _reg)	(((_reg) & (_mask)) >> (ffs(_mask) - 1))
-#define field_prep(_mask, _val)	(((_val) << (ffs(_mask) - 1)) & (_mask))
-
 #define GPIO_G7_IRQ_STS_BASE 0x100
 #define GPIO_G7_IRQ_STS_OFFSET(x) (GPIO_G7_IRQ_STS_BASE + (x) * 0x4)
 #define GPIO_G7_CTRL_REG_BASE 0x180
diff --git a/drivers/iio/dac/ad3530r.c b/drivers/iio/dac/ad3530r.c
index 6134613777b8..b97b46090d80 100644
--- a/drivers/iio/dac/ad3530r.c
+++ b/drivers/iio/dac/ad3530r.c
@@ -53,9 +53,6 @@
 #define AD3530R_MAX_CHANNELS			8
 #define AD3531R_MAX_CHANNELS			4
 
-/* Non-constant mask variant of FIELD_PREP() */
-#define field_prep(_mask, _val)	(((_val) << (ffs(_mask) - 1)) & (_mask))
-
 enum ad3530r_mode {
 	AD3530R_NORMAL_OP,
 	AD3530R_POWERDOWN_1K,
diff --git a/drivers/iio/temperature/mlx90614.c b/drivers/iio/temperature/mlx90614.c
index 8a44a00bfd5e..1ad21b73e1b4 100644
--- a/drivers/iio/temperature/mlx90614.c
+++ b/drivers/iio/temperature/mlx90614.c
@@ -22,6 +22,7 @@
  * the "wakeup" GPIO is not given, power management will be disabled.
  */
 
+#include <linux/bitfield.h>
 #include <linux/delay.h>
 #include <linux/err.h>
 #include <linux/gpio/consumer.h>
@@ -68,10 +69,6 @@
 #define MLX90614_CONST_SCALE 20 /* Scale in milliKelvin (0.02 * 1000) */
 #define MLX90614_CONST_FIR 0x7 /* Fixed value for FIR part of low pass filter */
 
-/* Non-constant mask variant of FIELD_GET() and FIELD_PREP() */
-#define field_get(_mask, _reg)	(((_reg) & (_mask)) >> (ffs(_mask) - 1))
-#define field_prep(_mask, _val)	(((_val) << (ffs(_mask) - 1)) & (_mask))
-
 struct mlx_chip_info {
 	/* EEPROM offsets with 16-bit data, MSB first */
 	/* emissivity correction coefficient */
diff --git a/drivers/pinctrl/nuvoton/pinctrl-ma35.c b/drivers/pinctrl/nuvoton/pinctrl-ma35.c
index cdad01d68a37..8d71dc53cc1d 100644
--- a/drivers/pinctrl/nuvoton/pinctrl-ma35.c
+++ b/drivers/pinctrl/nuvoton/pinctrl-ma35.c
@@ -81,10 +81,6 @@
 #define MVOLT_1800			0
 #define MVOLT_3300			1
 
-/* Non-constant mask variant of FIELD_GET() and FIELD_PREP() */
-#define field_get(_mask, _reg)	(((_reg) & (_mask)) >> (ffs(_mask) - 1))
-#define field_prep(_mask, _val)	(((_val) << (ffs(_mask) - 1)) & (_mask))
-
 static const char * const gpio_group_name[] = {
 	"gpioa", "gpiob", "gpioc", "gpiod", "gpioe", "gpiof", "gpiog",
 	"gpioh", "gpioi", "gpioj", "gpiok", "gpiol", "gpiom", "gpion",
diff --git a/drivers/soc/renesas/renesas-soc.c b/drivers/soc/renesas/renesas-soc.c
index 1eb52356b996..ee4f17bb4db4 100644
--- a/drivers/soc/renesas/renesas-soc.c
+++ b/drivers/soc/renesas/renesas-soc.c
@@ -5,6 +5,7 @@
  * Copyright (C) 2014-2016 Glider bvba
  */
 
+#include <linux/bitfield.h>
 #include <linux/io.h>
 #include <linux/of.h>
 #include <linux/of_address.h>
@@ -524,8 +525,7 @@ static int __init renesas_soc_init(void)
 							   eshi, eslo);
 		}
 
-		if (soc->id &&
-		    ((product & id->mask) >> __ffs(id->mask)) != soc->id) {
+		if (soc->id && field_get(id->mask, product) != soc->id) {
 			pr_warn("SoC mismatch (product = 0x%x)\n", product);
 			ret = -ENODEV;
 			goto free_soc_dev_attr;
diff --git a/drivers/soc/renesas/rz-sysc.c b/drivers/soc/renesas/rz-sysc.c
index 19c1e666279b..ae727d9c8cc5 100644
--- a/drivers/soc/renesas/rz-sysc.c
+++ b/drivers/soc/renesas/rz-sysc.c
@@ -5,6 +5,7 @@
  * Copyright (C) 2024 Renesas Electronics Corp.
  */
 
+#include <linux/bitfield.h>
 #include <linux/cleanup.h>
 #include <linux/io.h>
 #include <linux/mfd/syscon.h>
@@ -16,8 +17,6 @@
 
 #include "rz-sysc.h"
 
-#define field_get(_mask, _reg) (((_reg) & (_mask)) >> (ffs(_mask) - 1))
-
 /**
  * struct rz_sysc - RZ SYSC private data structure
  * @base: SYSC base address
diff --git a/include/linux/bitfield.h b/include/linux/bitfield.h
index 5355f8f806a9..126dc5b380af 100644
--- a/include/linux/bitfield.h
+++ b/include/linux/bitfield.h
@@ -17,6 +17,7 @@
  * FIELD_{GET,PREP} macros take as first parameter shifted mask
  * from which they extract the base mask and shift amount.
  * Mask must be a compilation time constant.
+ * field_{get,prep} are variants that take a non-const mask.
  *
  * Example:
  *
@@ -60,7 +61,7 @@
 
 #define __bf_cast_unsigned(type, x)	((__unsigned_scalar_typeof(type))(x))
 
-#define __BF_FIELD_CHECK(_mask, _reg, _val, _pfx)			\
+#define __BF_FIELD_CHECK_MASK(_mask, _val, _pfx)			\
 	({								\
 		BUILD_BUG_ON_MSG(!__builtin_constant_p(_mask),		\
 				 _pfx "mask is not constant");		\
@@ -69,13 +70,33 @@
 				 ~((_mask) >> __bf_shf(_mask)) &	\
 					(0 + (_val)) : 0,		\
 				 _pfx "value too large for the field"); \
-		BUILD_BUG_ON_MSG(__bf_cast_unsigned(_mask, _mask) >	\
-				 __bf_cast_unsigned(_reg, ~0ull),	\
-				 _pfx "type of reg too small for mask"); \
 		__BUILD_BUG_ON_NOT_POWER_OF_2((_mask) +			\
 					      (1ULL << __bf_shf(_mask))); \
 	})
 
+#define __BF_FIELD_CHECK_REG(mask, reg, pfx)				\
+	BUILD_BUG_ON_MSG(__bf_cast_unsigned(mask, mask) >		\
+			 __bf_cast_unsigned(reg, ~0ull),		\
+			 pfx "type of reg too small for mask")
+
+#define __BF_FIELD_CHECK(mask, reg, val, pfx)				\
+	({								\
+		__BF_FIELD_CHECK_MASK(mask, val, pfx);			\
+		__BF_FIELD_CHECK_REG(mask, reg, pfx);			\
+	})
+
+#define __FIELD_PREP(mask, val, pfx)					\
+	({								\
+		__BF_FIELD_CHECK_MASK(mask, val, pfx);			\
+		((typeof(mask))(val) << __bf_shf(mask)) & (mask);	\
+	})
+
+#define __FIELD_GET(mask, reg, pfx)					\
+	({								\
+		__BF_FIELD_CHECK_MASK(mask, 0U, pfx);			\
+		(typeof(mask))(((reg) & (mask)) >> __bf_shf(mask));	\
+	})
+
 /**
  * FIELD_MAX() - produce the maximum value representable by a field
  * @_mask: shifted mask defining the field's length and position
@@ -112,8 +133,8 @@
  */
 #define FIELD_PREP(_mask, _val)						\
 	({								\
-		__BF_FIELD_CHECK(_mask, 0ULL, _val, "FIELD_PREP: ");	\
-		((typeof(_mask))(_val) << __bf_shf(_mask)) & (_mask);	\
+		__BF_FIELD_CHECK_REG(_mask, 0ULL, "FIELD_PREP: ");	\
+		__FIELD_PREP(_mask, _val, "FIELD_PREP: ");		\
 	})
 
 #define __BF_CHECK_POW2(n)	BUILD_BUG_ON_ZERO(((n) & ((n) - 1)) != 0)
@@ -152,8 +173,8 @@
  */
 #define FIELD_GET(_mask, _reg)						\
 	({								\
-		__BF_FIELD_CHECK(_mask, _reg, 0U, "FIELD_GET: ");	\
-		(typeof(_mask))(((_reg) & (_mask)) >> __bf_shf(_mask));	\
+		__BF_FIELD_CHECK_REG(_mask, _reg, "FIELD_GET: ");	\
+		__FIELD_GET(_mask, _reg, "FIELD_GET: ");		\
 	})
 
 /**
@@ -220,4 +241,62 @@ __MAKE_OP(64)
 #undef __MAKE_OP
 #undef ____MAKE_OP
 
+#define __field_prep(mask, val)						\
+	({								\
+		__auto_type __mask = (mask);				\
+		typeof(__mask) __val = (val);				\
+		unsigned int __shift = BITS_PER_TYPE(__mask) <= 32 ?	\
+				       __ffs(__mask) : __ffs64(__mask);	\
+		(__val << __shift) & __mask;				\
+	})
+
+#define __field_get(mask, reg)						\
+	({								\
+		__auto_type __mask = (mask);				\
+		typeof(__mask) __reg =  (reg);				\
+		unsigned int __shift = BITS_PER_TYPE(__mask) <= 32 ?	\
+				       __ffs(__mask) : __ffs64(__mask);	\
+		(__reg & __mask) >> __shift;				\
+	})
+
+/**
+ * field_prep() - prepare a bitfield element
+ * @mask: shifted mask defining the field's length and position, must be
+ *        non-zero
+ * @val:  value to put in the field
+ *
+ * Return: field value masked and shifted to its final destination
+ *
+ * field_prep() masks and shifts up the value.  The result should be
+ * combined with other fields of the bitfield using logical OR.
+ * Unlike FIELD_PREP(), @mask is not limited to a compile-time constant.
+ * Typical usage patterns are a value stored in a table, or calculated by
+ * shifting a constant by a variable number of bits.
+ * If you want to ensure that @mask is a compile-time constant, please use
+ * FIELD_PREP() directly instead.
+ */
+#define field_prep(mask, val)						\
+	(__builtin_constant_p(mask) ? __FIELD_PREP(mask, val, "field_prep: ") \
+				    : __field_prep(mask, val))
+
+/**
+ * field_get() - extract a bitfield element
+ * @mask: shifted mask defining the field's length and position, must be
+ *        non-zero
+ * @reg:  value of entire bitfield
+ *
+ * Return: extracted field value
+ *
+ * field_get() extracts the field specified by @mask from the
+ * bitfield passed in as @reg by masking and shifting it down.
+ * Unlike FIELD_GET(), @mask is not limited to a compile-time constant.
+ * Typical usage patterns are a value stored in a table, or calculated by
+ * shifting a constant by a variable number of bits.
+ * If you want to ensure that @mask is a compile-time constant, please use
+ * FIELD_GET() directly instead.
+ */
+#define field_get(mask, reg)						\
+	(__builtin_constant_p(mask) ? __FIELD_GET(mask, reg, "field_get: ") \
+				    : __field_get(mask, reg))
+
 #endif
diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h
index afedfd5bea07..80211900f373 100644
--- a/include/linux/cpumask.h
+++ b/include/linux/cpumask.h
@@ -7,14 +7,16 @@
  * set of CPUs in a system, one bit position per CPU number.  In general,
  * only nr_cpu_ids (<= NR_CPUS) bits are valid.
  */
-#include <linux/cleanup.h>
-#include <linux/kernel.h>
+#include <linux/atomic.h>
 #include <linux/bitmap.h>
+#include <linux/cleanup.h>
 #include <linux/cpumask_types.h>
-#include <linux/atomic.h>
-#include <linux/bug.h>
 #include <linux/gfp_types.h>
 #include <linux/numa.h>
+#include <linux/threads.h>
+#include <linux/types.h>
+
+#include <asm/bug.h>
 
 /**
  * cpumask_pr_args - printf args to output a cpumask
diff --git a/include/linux/nodemask.h b/include/linux/nodemask.h
index 7ad1f5c7407e..bd38648c998d 100644
--- a/include/linux/nodemask.h
+++ b/include/linux/nodemask.h
@@ -245,18 +245,18 @@ static __always_inline int __nodes_weight(const nodemask_t *srcp, unsigned int n
 }
 
 /* FIXME: better would be to fix all architectures to never return
-          > MAX_NUMNODES, then the silly min_ts could be dropped. */
+          > MAX_NUMNODES, then the silly min()s could be dropped. */
 
 #define first_node(src) __first_node(&(src))
 static __always_inline unsigned int __first_node(const nodemask_t *srcp)
 {
-	return min_t(unsigned int, MAX_NUMNODES, find_first_bit(srcp->bits, MAX_NUMNODES));
+	return min(MAX_NUMNODES, find_first_bit(srcp->bits, MAX_NUMNODES));
 }
 
 #define next_node(n, src) __next_node((n), &(src))
 static __always_inline unsigned int __next_node(int n, const nodemask_t *srcp)
 {
-	return min_t(unsigned int, MAX_NUMNODES, find_next_bit(srcp->bits, MAX_NUMNODES, n+1));
+	return min(MAX_NUMNODES, find_next_bit(srcp->bits, MAX_NUMNODES, n+1));
 }
 
 /*
@@ -293,8 +293,7 @@ static __always_inline void init_nodemask_of_node(nodemask_t *mask, int node)
 #define first_unset_node(mask) __first_unset_node(&(mask))
 static __always_inline unsigned int __first_unset_node(const nodemask_t *maskp)
 {
-	return min_t(unsigned int, MAX_NUMNODES,
-			find_first_zero_bit(maskp->bits, MAX_NUMNODES));
+	return min(MAX_NUMNODES, find_first_zero_bit(maskp->bits, MAX_NUMNODES));
 }
 
 #define NODE_MASK_LAST_WORD BITMAP_LAST_WORD_MASK(MAX_NUMNODES)
diff --git a/lib/hweight.c b/lib/hweight.c
index c94586b62551..0dfcafc3fd39 100644
--- a/lib/hweight.c
+++ b/lib/hweight.c
@@ -4,8 +4,8 @@
 #include <asm/types.h>
 
 /**
- * hweightN - returns the hamming weight of a N-bit word
- * @x: the word to weigh
+ * DOC: __sw_hweightN - returns the hamming weight of a N-bit word
+ * @w: the word to weigh
  *
  * The Hamming Weight of a number is the total number of bits set in it.
  */
diff --git a/rust/kernel/bitmap.rs b/rust/kernel/bitmap.rs
index aa8fc7bf06fc..83d7dea99137 100644
--- a/rust/kernel/bitmap.rs
+++ b/rust/kernel/bitmap.rs
@@ -12,8 +12,6 @@ use crate::bindings;
 use crate::pr_err;
 use core::ptr::NonNull;
 
-const BITS_PER_LONG: usize = bindings::BITS_PER_LONG as usize;
-
 /// Represents a C bitmap. Wraps underlying C bitmap API.
 ///
 /// # Invariants
@@ -149,14 +147,14 @@ macro_rules! bitmap_assert_return {
 ///
 /// # Invariants
 ///
-/// * `nbits` is `<= i32::MAX` and never changes.
-/// * if `nbits <= bindings::BITS_PER_LONG`, then `repr` is a `usize`.
+/// * `nbits` is `<= MAX_LEN`.
+/// * if `nbits <= MAX_INLINE_LEN`, then `repr` is a `usize`.
 /// * otherwise, `repr` holds a non-null pointer to an initialized
 ///   array of `unsigned long` that is large enough to hold `nbits` bits.
 pub struct BitmapVec {
     /// Representation of bitmap.
     repr: BitmapRepr,
-    /// Length of this bitmap. Must be `<= i32::MAX`.
+    /// Length of this bitmap. Must be `<= MAX_LEN`.
     nbits: usize,
 }
 
@@ -164,7 +162,7 @@ impl core::ops::Deref for BitmapVec {
     type Target = Bitmap;
 
     fn deref(&self) -> &Bitmap {
-        let ptr = if self.nbits <= BITS_PER_LONG {
+        let ptr = if self.nbits <= BitmapVec::MAX_INLINE_LEN {
             // SAFETY: Bitmap is represented inline.
             #[allow(unused_unsafe, reason = "Safe since Rust 1.92.0")]
             unsafe {
@@ -183,7 +181,7 @@ impl core::ops::Deref for BitmapVec {
 
 impl core::ops::DerefMut for BitmapVec {
     fn deref_mut(&mut self) -> &mut Bitmap {
-        let ptr = if self.nbits <= BITS_PER_LONG {
+        let ptr = if self.nbits <= BitmapVec::MAX_INLINE_LEN {
             // SAFETY: Bitmap is represented inline.
             #[allow(unused_unsafe, reason = "Safe since Rust 1.92.0")]
             unsafe {
@@ -213,7 +211,7 @@ unsafe impl Sync for BitmapVec {}
 
 impl Drop for BitmapVec {
     fn drop(&mut self) {
-        if self.nbits <= BITS_PER_LONG {
+        if self.nbits <= BitmapVec::MAX_INLINE_LEN {
             return;
         }
         // SAFETY: `self.ptr` was returned by the C `bitmap_zalloc`.
@@ -226,23 +224,39 @@ impl Drop for BitmapVec {
 }
 
 impl BitmapVec {
+    /// The maximum possible length of a `BitmapVec`.
+    pub const MAX_LEN: usize = i32::MAX as usize;
+
+    /// The maximum length that uses the inline representation.
+    pub const MAX_INLINE_LEN: usize = usize::BITS as usize;
+
+    /// Construct a longest possible inline [`BitmapVec`].
+    #[inline]
+    pub fn new_inline() -> Self {
+        // INVARIANT: `nbits <= MAX_INLINE_LEN`, so an inline bitmap is the right repr.
+        BitmapVec {
+            repr: BitmapRepr { bitmap: 0 },
+            nbits: BitmapVec::MAX_INLINE_LEN,
+        }
+    }
+
     /// Constructs a new [`BitmapVec`].
     ///
     /// Fails with [`AllocError`] when the [`BitmapVec`] could not be allocated. This
-    /// includes the case when `nbits` is greater than `i32::MAX`.
+    /// includes the case when `nbits` is greater than `MAX_LEN`.
     #[inline]
     pub fn new(nbits: usize, flags: Flags) -> Result<Self, AllocError> {
-        if nbits <= BITS_PER_LONG {
+        if nbits <= BitmapVec::MAX_INLINE_LEN {
             return Ok(BitmapVec {
                 repr: BitmapRepr { bitmap: 0 },
                 nbits,
             });
         }
-        if nbits > i32::MAX.try_into().unwrap() {
+        if nbits > Self::MAX_LEN {
             return Err(AllocError);
         }
         let nbits_u32 = u32::try_from(nbits).unwrap();
-        // SAFETY: `BITS_PER_LONG < nbits` and `nbits <= i32::MAX`.
+        // SAFETY: `MAX_INLINE_LEN < nbits` and `nbits <= MAX_LEN`.
         let ptr = unsafe { bindings::bitmap_zalloc(nbits_u32, flags.as_raw()) };
         let ptr = NonNull::new(ptr).ok_or(AllocError)?;
         // INVARIANT: `ptr` returned by C `bitmap_zalloc` and `nbits` checked.
@@ -495,9 +509,10 @@ mod tests {
     #[test]
     fn bitmap_borrow() {
         let fake_bitmap: [usize; 2] = [0, 0];
+        let fake_bitmap_len = 2 * usize::BITS as usize;
         // SAFETY: `fake_c_bitmap` is an array of expected length.
-        let b = unsafe { Bitmap::from_raw(fake_bitmap.as_ptr(), 2 * BITS_PER_LONG) };
-        assert_eq!(2 * BITS_PER_LONG, b.len());
+        let b = unsafe { Bitmap::from_raw(fake_bitmap.as_ptr(), fake_bitmap_len) };
+        assert_eq!(fake_bitmap_len, b.len());
         assert_eq!(None, b.next_bit(0));
     }
 
diff --git a/rust/kernel/id_pool.rs b/rust/kernel/id_pool.rs
index a41a3404213c..384753fe0e44 100644
--- a/rust/kernel/id_pool.rs
+++ b/rust/kernel/id_pool.rs
@@ -7,8 +7,6 @@
 use crate::alloc::{AllocError, Flags};
 use crate::bitmap::BitmapVec;
 
-const BITS_PER_LONG: usize = bindings::BITS_PER_LONG as usize;
-
 /// Represents a dynamic ID pool backed by a [`BitmapVec`].
 ///
 /// Clients acquire and release IDs from unset bits in a bitmap.
@@ -25,22 +23,22 @@ const BITS_PER_LONG: usize = bindings::BITS_PER_LONG as usize;
 /// Basic usage
 ///
 /// ```
-/// use kernel::alloc::{AllocError, flags::GFP_KERNEL};
-/// use kernel::id_pool::IdPool;
+/// use kernel::alloc::AllocError;
+/// use kernel::id_pool::{IdPool, UnusedId};
 ///
-/// let mut pool = IdPool::new(64, GFP_KERNEL)?;
+/// let mut pool = IdPool::with_capacity(64, GFP_KERNEL)?;
 /// for i in 0..64 {
-///     assert_eq!(i, pool.acquire_next_id(i).ok_or(ENOSPC)?);
+///     assert_eq!(i, pool.find_unused_id(i).ok_or(ENOSPC)?.acquire());
 /// }
 ///
 /// pool.release_id(23);
-/// assert_eq!(23, pool.acquire_next_id(0).ok_or(ENOSPC)?);
+/// assert_eq!(23, pool.find_unused_id(0).ok_or(ENOSPC)?.acquire());
 ///
-/// assert_eq!(None, pool.acquire_next_id(0));  // time to realloc.
+/// assert!(pool.find_unused_id(0).is_none());  // time to realloc.
 /// let resizer = pool.grow_request().ok_or(ENOSPC)?.realloc(GFP_KERNEL)?;
 /// pool.grow(resizer);
 ///
-/// assert_eq!(pool.acquire_next_id(0), Some(64));
+/// assert_eq!(pool.find_unused_id(0).ok_or(ENOSPC)?.acquire(), 64);
 /// # Ok::<(), Error>(())
 /// ```
 ///
@@ -54,8 +52,8 @@ const BITS_PER_LONG: usize = bindings::BITS_PER_LONG as usize;
 /// fn get_id_maybe_realloc(guarded_pool: &SpinLock<IdPool>) -> Result<usize, AllocError> {
 ///     let mut pool = guarded_pool.lock();
 ///     loop {
-///         match pool.acquire_next_id(0) {
-///             Some(index) => return Ok(index),
+///         match pool.find_unused_id(0) {
+///             Some(index) => return Ok(index.acquire()),
 ///             None => {
 ///                 let alloc_request = pool.grow_request();
 ///                 drop(pool);
@@ -97,13 +95,24 @@ impl ReallocRequest {
 impl IdPool {
     /// Constructs a new [`IdPool`].
     ///
-    /// A capacity below [`BITS_PER_LONG`] is adjusted to
-    /// [`BITS_PER_LONG`].
+    /// The pool will have a capacity of [`MAX_INLINE_LEN`].
+    ///
+    /// [`MAX_INLINE_LEN`]: BitmapVec::MAX_INLINE_LEN
+    #[inline]
+    pub fn new() -> Self {
+        Self {
+            map: BitmapVec::new_inline(),
+        }
+    }
+
+    /// Constructs a new [`IdPool`] with space for a specific number of bits.
+    ///
+    /// A capacity below [`MAX_INLINE_LEN`] is adjusted to [`MAX_INLINE_LEN`].
     ///
-    /// [`BITS_PER_LONG`]: srctree/include/asm-generic/bitsperlong.h
+    /// [`MAX_INLINE_LEN`]: BitmapVec::MAX_INLINE_LEN
     #[inline]
-    pub fn new(num_ids: usize, flags: Flags) -> Result<Self, AllocError> {
-        let num_ids = core::cmp::max(num_ids, BITS_PER_LONG);
+    pub fn with_capacity(num_ids: usize, flags: Flags) -> Result<Self, AllocError> {
+        let num_ids = usize::max(num_ids, BitmapVec::MAX_INLINE_LEN);
         let map = BitmapVec::new(num_ids, flags)?;
         Ok(Self { map })
     }
@@ -116,28 +125,34 @@ impl IdPool {
 
     /// Returns a [`ReallocRequest`] if the [`IdPool`] can be shrunk, [`None`] otherwise.
     ///
-    /// The capacity of an [`IdPool`] cannot be shrunk below [`BITS_PER_LONG`].
+    /// The capacity of an [`IdPool`] cannot be shrunk below [`MAX_INLINE_LEN`].
     ///
-    /// [`BITS_PER_LONG`]: srctree/include/asm-generic/bitsperlong.h
+    /// [`MAX_INLINE_LEN`]: BitmapVec::MAX_INLINE_LEN
     ///
     /// # Examples
     ///
     /// ```
-    /// use kernel::alloc::{AllocError, flags::GFP_KERNEL};
-    /// use kernel::id_pool::{ReallocRequest, IdPool};
+    /// use kernel::{
+    ///     alloc::AllocError,
+    ///     bitmap::BitmapVec,
+    ///     id_pool::{
+    ///         IdPool,
+    ///         ReallocRequest,
+    ///     },
+    /// };
     ///
-    /// let mut pool = IdPool::new(1024, GFP_KERNEL)?;
+    /// let mut pool = IdPool::with_capacity(1024, GFP_KERNEL)?;
     /// let alloc_request = pool.shrink_request().ok_or(AllocError)?;
     /// let resizer = alloc_request.realloc(GFP_KERNEL)?;
     /// pool.shrink(resizer);
-    /// assert_eq!(pool.capacity(), kernel::bindings::BITS_PER_LONG as usize);
+    /// assert_eq!(pool.capacity(), BitmapVec::MAX_INLINE_LEN);
     /// # Ok::<(), AllocError>(())
     /// ```
     #[inline]
     pub fn shrink_request(&self) -> Option<ReallocRequest> {
         let cap = self.capacity();
-        // Shrinking below [`BITS_PER_LONG`] is never possible.
-        if cap <= BITS_PER_LONG {
+        // Shrinking below `MAX_INLINE_LEN` is never possible.
+        if cap <= BitmapVec::MAX_INLINE_LEN {
             return None;
         }
         // Determine if the bitmap can shrink based on the position of
@@ -146,13 +161,13 @@ impl IdPool {
         // bitmap should shrink to half its current size.
         let Some(bit) = self.map.last_bit() else {
             return Some(ReallocRequest {
-                num_ids: BITS_PER_LONG,
+                num_ids: BitmapVec::MAX_INLINE_LEN,
             });
         };
         if bit >= (cap / 4) {
             return None;
         }
-        let num_ids = usize::max(BITS_PER_LONG, cap / 2);
+        let num_ids = usize::max(BitmapVec::MAX_INLINE_LEN, cap / 2);
         Some(ReallocRequest { num_ids })
     }
 
@@ -177,11 +192,13 @@ impl IdPool {
 
     /// Returns a [`ReallocRequest`] for growing this [`IdPool`], if possible.
     ///
-    /// The capacity of an [`IdPool`] cannot be grown above [`i32::MAX`].
+    /// The capacity of an [`IdPool`] cannot be grown above [`MAX_LEN`].
+    ///
+    /// [`MAX_LEN`]: BitmapVec::MAX_LEN
     #[inline]
     pub fn grow_request(&self) -> Option<ReallocRequest> {
         let num_ids = self.capacity() * 2;
-        if num_ids > i32::MAX.try_into().unwrap() {
+        if num_ids > BitmapVec::MAX_LEN {
             return None;
         }
         Some(ReallocRequest { num_ids })
@@ -204,18 +221,18 @@ impl IdPool {
         self.map = resizer.new;
     }
 
-    /// Acquires a new ID by finding and setting the next zero bit in the
-    /// bitmap.
+    /// Finds an unused ID in the bitmap.
     ///
     /// Upon success, returns its index. Otherwise, returns [`None`]
     /// to indicate that a [`Self::grow_request`] is needed.
     #[inline]
-    pub fn acquire_next_id(&mut self, offset: usize) -> Option<usize> {
-        let next_zero_bit = self.map.next_zero_bit(offset);
-        if let Some(nr) = next_zero_bit {
-            self.map.set_bit(nr);
-        }
-        next_zero_bit
+    #[must_use]
+    pub fn find_unused_id(&mut self, offset: usize) -> Option<UnusedId<'_>> {
+        // INVARIANT: `next_zero_bit()` returns None or an integer less than `map.len()`
+        Some(UnusedId {
+            id: self.map.next_zero_bit(offset)?,
+            pool: self,
+        })
     }
 
     /// Releases an ID.
@@ -224,3 +241,55 @@ impl IdPool {
         self.map.clear_bit(id);
     }
 }
+
+/// Represents an unused id in an [`IdPool`].
+///
+/// # Invariants
+///
+/// The value of `id` is less than `pool.map.len()`.
+pub struct UnusedId<'pool> {
+    id: usize,
+    pool: &'pool mut IdPool,
+}
+
+impl<'pool> UnusedId<'pool> {
+    /// Get the unused id as an usize.
+    ///
+    /// Be aware that the id has not yet been acquired in the pool. The
+    /// [`acquire`] method must be called to prevent others from taking the id.
+    ///
+    /// [`acquire`]: UnusedId::acquire()
+    #[inline]
+    #[must_use]
+    pub fn as_usize(&self) -> usize {
+        self.id
+    }
+
+    /// Get the unused id as an u32.
+    ///
+    /// Be aware that the id has not yet been acquired in the pool. The
+    /// [`acquire`] method must be called to prevent others from taking the id.
+    ///
+    /// [`acquire`]: UnusedId::acquire()
+    #[inline]
+    #[must_use]
+    pub fn as_u32(&self) -> u32 {
+        // CAST: By the type invariants:
+        // `self.id < pool.map.len() <= BitmapVec::MAX_LEN = i32::MAX`.
+        self.id as u32
+    }
+
+    /// Acquire the unused id.
+    #[inline]
+    pub fn acquire(self) -> usize {
+        self.pool.map.set_bit(self.id);
+        self.id
+    }
+}
+
+impl Default for IdPool {
+    #[inline]
+    fn default() -> Self {
+        Self::new()
+    }
+}
diff --git a/sound/usb/mixer_quirks.c b/sound/usb/mixer_quirks.c
index fe6c2cebc7f0..f7189990dd6a 100644
--- a/sound/usb/mixer_quirks.c
+++ b/sound/usb/mixer_quirks.c
@@ -3416,10 +3416,6 @@ static int snd_bbfpro_controls_create(struct usb_mixer_interface *mixer)
 #define RME_DIGIFACE_REGISTER(reg, mask) (((reg) << 16) | (mask))
 #define RME_DIGIFACE_INVERT BIT(31)
 
-/* Nonconst helpers */
-#define field_get(_mask, _reg) (((_reg) & (_mask)) >> (ffs(_mask) - 1))
-#define field_prep(_mask, _val) (((_val) << (ffs(_mask) - 1)) & (_mask))
-
 static int snd_rme_digiface_write_reg(struct snd_kcontrol *kcontrol, int item, u16 mask, u16 val)
 {
 	struct usb_mixer_elem_list *list = snd_kcontrol_chip(kcontrol);