[PATCH 56/79] block: rust: add abstraction for block queue feature flags

[Andreas Hindborg]

Add the `Feature` enum and `Features` type as Rust abstractions for the
C `blk_features_t` bitfield. These types wrap the `BLK_FEAT_*` flags
and allow drivers to describe block device capabilities such as write
cache support, FUA, rotational media, and DAX.

Signed-off-by: Andreas Hindborg <a.hindborg@xxxxxxxxxx>
---
 rust/bindings/bindings_helper.h | 15 ++++++++-
 rust/kernel/block/mq.rs         |  2 ++
 rust/kernel/block/mq/feature.rs | 73 +++++++++++++++++++++++++++++++++++++++++
 3 files changed, 89 insertions(+), 1 deletion(-)

diff --git a/rust/bindings/bindings_helper.h b/rust/bindings/bindings_helper.h
index b8c2f3eadc730..209c53443e9cb 100644
--- a/rust/bindings/bindings_helper.h
+++ b/rust/bindings/bindings_helper.h
@@ -113,7 +113,6 @@ const gfp_t RUST_CONST_HELPER_GFP_NOWAIT = GFP_NOWAIT;
 const gfp_t RUST_CONST_HELPER___GFP_ZERO = __GFP_ZERO;
 const gfp_t RUST_CONST_HELPER___GFP_HIGHMEM = ___GFP_HIGHMEM;
 const gfp_t RUST_CONST_HELPER___GFP_NOWARN = ___GFP_NOWARN;
-const blk_features_t RUST_CONST_HELPER_BLK_FEAT_ROTATIONAL = BLK_FEAT_ROTATIONAL;
 const blk_status_t RUST_CONST_HELPER_BLK_STS_OK = BLK_STS_OK;
 const blk_status_t RUST_CONST_HELPER_BLK_STS_NOTSUPP = BLK_STS_NOTSUPP;
 const blk_status_t RUST_CONST_HELPER_BLK_STS_TIMEOUT = BLK_STS_TIMEOUT;
@@ -133,7 +132,21 @@ const blk_status_t RUST_CONST_HELPER_BLK_STS_ZONE_ACTIVE_RESOURCE = BLK_STS_ZONE
 const blk_status_t RUST_CONST_HELPER_BLK_STS_OFFLINE = BLK_STS_OFFLINE;
 const blk_status_t RUST_CONST_HELPER_BLK_STS_DURATION_LIMIT = BLK_STS_DURATION_LIMIT;
 const blk_status_t RUST_CONST_HELPER_BLK_STS_INVAL = BLK_STS_INVAL;
+const blk_features_t RUST_CONST_HELPER_BLK_FEAT_WRITE_CACHE = BLK_FEAT_WRITE_CACHE;
+const blk_features_t RUST_CONST_HELPER_BLK_FEAT_FUA = BLK_FEAT_FUA;
+const blk_features_t RUST_CONST_HELPER_BLK_FEAT_ROTATIONAL = BLK_FEAT_ROTATIONAL;
+const blk_features_t RUST_CONST_HELPER_BLK_FEAT_ADD_RANDOM = BLK_FEAT_ADD_RANDOM;
+const blk_features_t RUST_CONST_HELPER_BLK_FEAT_IO_STAT = BLK_FEAT_IO_STAT;
+const blk_features_t RUST_CONST_HELPER_BLK_FEAT_STABLE_WRITES = BLK_FEAT_STABLE_WRITES;
+const blk_features_t RUST_CONST_HELPER_BLK_FEAT_SYNCHRONOUS = BLK_FEAT_SYNCHRONOUS;
+const blk_features_t RUST_CONST_HELPER_BLK_FEAT_NOWAIT = BLK_FEAT_NOWAIT;
+const blk_features_t RUST_CONST_HELPER_BLK_FEAT_DAX = BLK_FEAT_DAX;
+const blk_features_t RUST_CONST_HELPER_BLK_FEAT_POLL = BLK_FEAT_POLL;
 const blk_features_t RUST_CONST_HELPER_BLK_FEAT_ZONED = BLK_FEAT_ZONED;
+const blk_features_t RUST_CONST_HELPER_BLK_FEAT_PCI_P2PDMA = BLK_FEAT_PCI_P2PDMA;
+const blk_features_t RUST_CONST_HELPER_BLK_FEAT_SKIP_TAGSET_QUIESCE = BLK_FEAT_SKIP_TAGSET_QUIESCE;
+const blk_features_t RUST_CONST_HELPER_BLK_FEAT_RAID_PARTIAL_STRIPES_EXPENSIVE = BLK_FEAT_RAID_PARTIAL_STRIPES_EXPENSIVE;
+const blk_features_t RUST_CONST_HELPER_BLK_FEAT_ATOMIC_WRITES = BLK_FEAT_ATOMIC_WRITES;
 const blk_opf_t RUST_CONST_HELPER_REQ_FAILFAST_DEV = REQ_FAILFAST_DEV;
 const blk_opf_t RUST_CONST_HELPER_REQ_FAILFAST_TRANSPORT = REQ_FAILFAST_TRANSPORT;
 const blk_opf_t RUST_CONST_HELPER_REQ_FAILFAST_DRIVER = REQ_FAILFAST_DRIVER;
diff --git a/rust/kernel/block/mq.rs b/rust/kernel/block/mq.rs
index 5a1c8e914bb9e..b36112f7b22b9 100644
--- a/rust/kernel/block/mq.rs
+++ b/rust/kernel/block/mq.rs
@@ -125,12 +125,14 @@
 //! # Ok::<(), kernel::error::Error>(())
 //! ```
 
+mod feature;
 pub mod gen_disk;
 mod operations;
 mod request;
 mod request_queue;
 pub mod tag_set;
 
+pub use feature::{Feature, Features};
 pub use operations::IoCompletionBatch;
 pub use operations::Operations;
 pub use request::Command;
diff --git a/rust/kernel/block/mq/feature.rs b/rust/kernel/block/mq/feature.rs
new file mode 100644
index 0000000000000..6c9f098e10c55
--- /dev/null
+++ b/rust/kernel/block/mq/feature.rs
@@ -0,0 +1,73 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! Block device feature flags.
+//!
+//! This module provides Rust abstractions for the C `blk_features_t` type and
+//! the associated `BLK_FEAT_*` flags defined in `include/linux/blkdev.h`.
+
+use kernel::prelude::*;
+
+impl_flags! {
+    /// A set of block device feature flags.
+    ///
+    /// This type wraps the C `blk_features_t` bitfield and represents a
+    /// combination of zero or more [`Feature`] flags. It is used to describe
+    /// the capabilities of a block device in [`struct queue_limits`].
+    ///
+    /// [`struct queue_limits`]: srctree/include/linux/blkdev.h
+    #[derive(Debug, Clone, Default, Copy, PartialEq, Eq)]
+    pub struct Features(u32);
+
+    /// A block device feature flag.
+    ///
+    /// Each variant corresponds to a `BLK_FEAT_*` constant defined in
+    /// `include/linux/blkdev.h`. These flags describe individual capabilities
+    /// or properties of a block device.
+    #[derive(Debug, Clone, Copy, PartialEq, Eq)]
+    pub enum Feature {
+        /// Supports a volatile write cache.
+        WriteCache = bindings::BLK_FEAT_WRITE_CACHE,
+
+        /// Supports passing on the FUA bit.
+        ForcedUnitAccess = bindings::BLK_FEAT_FUA,
+
+        /// Rotational device (hard drive or floppy).
+        Rotational = bindings::BLK_FEAT_ROTATIONAL,
+
+        /// Contributes to the random number pool.
+        AddRandom = bindings::BLK_FEAT_ADD_RANDOM,
+
+        /// Enables disk/partitions I/O accounting.
+        IoStat = bindings::BLK_FEAT_IO_STAT,
+
+        /// Don't modify data until writeback is done.
+        StableWrites = bindings::BLK_FEAT_STABLE_WRITES,
+
+        /// Always completes in submit context.
+        Synchronous = bindings::BLK_FEAT_SYNCHRONOUS,
+
+        /// Supports REQ_NOWAIT.
+        Nowait = bindings::BLK_FEAT_NOWAIT,
+
+        /// Supports DAX.
+        Dax = bindings::BLK_FEAT_DAX,
+
+        /// Supports I/O polling.
+        Poll = bindings::BLK_FEAT_POLL,
+
+        /// Is a zoned device.
+        Zoned = bindings::BLK_FEAT_ZONED,
+
+        /// Supports PCI(e) p2p requests.
+        PciP2Pdma = bindings::BLK_FEAT_PCI_P2PDMA,
+
+        /// Skips this queue in `blk_mq_(un)quiesce_tagset`.
+        SkipTagsetQuiesce = bindings::BLK_FEAT_SKIP_TAGSET_QUIESCE,
+
+        /// Undocumented magic for bcache.
+        RaidPartialStripesExpensive = bindings::BLK_FEAT_RAID_PARTIAL_STRIPES_EXPENSIVE,
+
+        /// Atomic writes enabled.
+        AtomicWrites = bindings::BLK_FEAT_ATOMIC_WRITES,
+    }
+}

-- 
2.51.2