| Message ID | 20220303201312.3255347-4-kbusch@kernel.org (mailing list archive) |
|---|---|
| State | Not Applicable |
| Delegated to: | Herbert Xu |
| Headers | show |
| Series | 64-bit data integrity field support | expand |
On 3/3/22 12:13, Keith Busch wrote: > The NVMe protocol extended the data integrity fields with unaligned > 48-bit reference tags. Provide some helper accessors in > preparation for these. Reviewed-by: Bart Van Assche <bvanassche@acm.org>
From: Keith Busch > Sent: 03 March 2022 20:13 > > The NVMe protocol extended the data integrity fields with unaligned > 48-bit reference tags. If they are reference tags, are they only interpreted by the sending system? In which case they don't need to be big-endian since the actual value doesn't really matter. > Provide some helper accessors in preparation for these. > ... > diff --git a/include/asm-generic/unaligned.h b/include/asm-generic/unaligned.h > index 1c4242416c9f..8fc637379899 100644 > --- a/include/asm-generic/unaligned.h > +++ b/include/asm-generic/unaligned.h > @@ -126,4 +126,30 @@ static inline void put_unaligned_le24(const u32 val, void *p) > __put_unaligned_le24(val, p); > } > > +static inline void __put_unaligned_be48(const u64 val, __u8 *p) > +{ > + *p++ = val >> 40; > + *p++ = val >> 32; > + *p++ = val >> 24; > + *p++ = val >> 16; > + *p++ = val >> 8; > + *p++ = val; > +} Although that matches __put_unaligned_be24() I think I'd use array indexing not pointer increments. The compiler will probably generate the same code anyway. However it is probably better to do: put_unaligned_be16(val >> 32, p); put_unaligned_be32(val, p + 2); so you get 2 memory accesses on x86 (etc) instead of 6. Similarly for __get_unaligned_be48() where it is likely so make a bigger difference. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)
David, > If they are reference tags, are they only interpreted by the sending > system? In which case they don't need to be big-endian since the > actual value doesn't really matter. The tags are validated by the storage device.
On Fri, Mar 04, 2022 at 01:31:26AM +0000, David Laight wrote: > From: Keith Busch > > Sent: 03 March 2022 20:13 > > > > The NVMe protocol extended the data integrity fields with unaligned > > 48-bit reference tags. > > If they are reference tags, are they only interpreted by the > sending system? No, this field participates in end-to-end data protection formats, so is verified on both sides.
diff --git a/include/asm-generic/unaligned.h b/include/asm-generic/unaligned.h index 1c4242416c9f..8fc637379899 100644 --- a/include/asm-generic/unaligned.h +++ b/include/asm-generic/unaligned.h @@ -126,4 +126,30 @@ static inline void put_unaligned_le24(const u32 val, void *p) __put_unaligned_le24(val, p); } +static inline void __put_unaligned_be48(const u64 val, __u8 *p) +{ + *p++ = val >> 40; + *p++ = val >> 32; + *p++ = val >> 24; + *p++ = val >> 16; + *p++ = val >> 8; + *p++ = val; +} + +static inline void put_unaligned_be48(const u64 val, void *p) +{ + __put_unaligned_be48(val, p); +} + +static inline u64 __get_unaligned_be48(const u8 *p) +{ + return (u64)p[0] << 40 | (u64)p[1] << 32 | p[2] << 24 | + p[3] << 16 | p[4] << 8 | p[5]; +} + +static inline u64 get_unaligned_be48(const void *p) +{ + return __get_unaligned_be48(p); +} + #endif /* __ASM_GENERIC_UNALIGNED_H */