When a C++ file compiled with -Wc++11-narrowing includes the UAPI header
linux/ublk_cmd.h, ublk_sqe_addr_to_auto_buf_reg()'s assignments of u64
values to u8, u16, and u32 fields result in compiler warnings. Add
explicit casts to the intended types to avoid these warnings. Drop the
unnecessary bitmasks.

Reported-by: Uday Shankar <ushankar@purestorage.com>
Signed-off-by: Caleb Sander Mateos <csander@purestorage.com>
Fixes: 99c1e4eb6a3f ("ublk: register buffer to local io_uring with provided buf index via UBLK_F_AUTO_BUF_REG")
---
 include/uapi/linux/ublk_cmd.h | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/include/uapi/linux/ublk_cmd.h b/include/uapi/linux/ublk_cmd.h
index 77d9d6af46da..c062109cb686 100644
--- a/include/uapi/linux/ublk_cmd.h
+++ b/include/uapi/linux/ublk_cmd.h
@@ -448,14 +448,14 @@ struct ublk_auto_buf_reg {
  */
 static inline struct ublk_auto_buf_reg ublk_sqe_addr_to_auto_buf_reg(
 		__u64 sqe_addr)
 {
 	struct ublk_auto_buf_reg reg = {
-		.index = sqe_addr & 0xffff,
-		.flags = (sqe_addr >> 16) & 0xff,
-		.reserved0 = (sqe_addr >> 24) & 0xff,
-		.reserved1 = sqe_addr >> 32,
+		.index = (__u16)sqe_addr,
+		.flags = (__u8)(sqe_addr >> 16),
+		.reserved0 = (__u8)(sqe_addr >> 24),
+		.reserved1 = (__u32)(sqe_addr >> 32),
 	};
 
 	return reg;
 }
 
-- 
2.45.2

On Sat, 21 Jun 2025 10:28:41 -0600, Caleb Sander Mateos wrote:
> When a C++ file compiled with -Wc++11-narrowing includes the UAPI header
> linux/ublk_cmd.h, ublk_sqe_addr_to_auto_buf_reg()'s assignments of u64
> values to u8, u16, and u32 fields result in compiler warnings. Add
> explicit casts to the intended types to avoid these warnings. Drop the
> unnecessary bitmasks.
> 
> 
> [...]

Applied, thanks!

[1/1] ublk: fix narrowing warnings in UAPI header
      commit: 03912ca894e4e5d6499bc57e9f10dda9f0965c1d

Best regards,
-- 
Jens Axboe

On Sat, Jun 21, 2025 at 10:28:41AM -0600, Caleb Sander Mateos wrote:
> When a C++ file compiled with -Wc++11-narrowing includes the UAPI header
> linux/ublk_cmd.h, ublk_sqe_addr_to_auto_buf_reg()'s assignments of u64
> values to u8, u16, and u32 fields result in compiler warnings. Add
> explicit casts to the intended types to avoid these warnings. Drop the
> unnecessary bitmasks.
> 
> Reported-by: Uday Shankar <ushankar@purestorage.com>
> Signed-off-by: Caleb Sander Mateos <csander@purestorage.com>
> Fixes: 99c1e4eb6a3f ("ublk: register buffer to local io_uring with provided buf index via UBLK_F_AUTO_BUF_REG")

Looks good: https://godbolt.org/z/qovrerdhd

Reviewed-by: Uday Shankar <ushankar@purestorage.com>

On Sat, Jun 21, 2025 at 10:28:41AM -0600, Caleb Sander Mateos wrote:
> When a C++ file compiled with -Wc++11-narrowing includes the UAPI header
> linux/ublk_cmd.h, ublk_sqe_addr_to_auto_buf_reg()'s assignments of u64
> values to u8, u16, and u32 fields result in compiler warnings. Add
> explicit casts to the intended types to avoid these warnings. Drop the
> unnecessary bitmasks.
> 
> Reported-by: Uday Shankar <ushankar@purestorage.com>
> Signed-off-by: Caleb Sander Mateos <csander@purestorage.com>
> Fixes: 99c1e4eb6a3f ("ublk: register buffer to local io_uring with provided buf index via UBLK_F_AUTO_BUF_REG")

Reviewed-by: Ming Lei <ming.lei@redhat.com>

thanks,
Ming