linux-kernel - [PATCHv4 4/8] linux/kernel: introduce lower_48

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Date:   Thu,  3 Mar 2022 12:13:08 -0800
From:   Keith Busch <kbusch@...nel.org>
To:     linux-nvme@...ts.infradead.org, linux-block@...r.kernel.org,
        linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     axboe@...nel.dk, hch@....de, martin.petersen@...cle.com,
        Keith Busch <kbusch@...nel.org>,
        Bart Van Assche <bvanassche@....org>
Subject: [PATCHv4 4/8] linux/kernel: introduce lower_48_bits function

Recent data integrity field enhancements allow reference tags to be up
to 48 bits. Introduce an inline helper function since this will be a
repeated operation.

Suggested-by: Bart Van Assche <bvanassche@....org>
Signed-off-by: Keith Busch <kbusch@...nel.org>
---
 include/linux/kernel.h | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index 33f47a996513..3877478681b9 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -63,6 +63,15 @@
 }					\
 )
 
+/**
+ * lower_48_bits() - return bits 0-47 of a number
+ * @n: the number we're accessing
+ */
+static inline u64 lower_48_bits(u64 n)
+{
+	return n & ((1ull << 48) - 1);
+}
+
 /**
  * upper_32_bits - return bits 32-63 of a number
  * @n: the number we're accessing
-- 
2.25.4