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author | Linus Torvalds <torvalds@linux-foundation.org> | 2016-05-28 16:15:25 -0700 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2016-05-28 16:15:25 -0700 |
commit | 7e0fb73c52c4037b4d5ef9ff56c7296a3151bd92 (patch) | |
tree | 9ab023505d388563d937b3c3ac26ef3c2045dba2 /drivers/media | |
parent | 4e8440b3b6b801953b2e53c55491cf98fc8f6c01 (diff) | |
parent | 4684fe95300c071983f77653e354c040fe80a265 (diff) | |
download | linux-7e0fb73c52c4037b4d5ef9ff56c7296a3151bd92.tar.bz2 |
Merge branch 'hash' of git://ftp.sciencehorizons.net/linux
Pull string hash improvements from George Spelvin:
"This series does several related things:
- Makes the dcache hash (fs/namei.c) useful for general kernel use.
(Thanks to Bruce for noticing the zero-length corner case)
- Converts the string hashes in <linux/sunrpc/svcauth.h> to use the
above.
- Avoids 64-bit multiplies in hash_64() on 32-bit platforms. Two
32-bit multiplies will do well enough.
- Rids the world of the bad hash multipliers in hash_32.
This finishes the job started in commit 689de1d6ca95 ("Minimal
fix-up of bad hashing behavior of hash_64()")
The vast majority of Linux architectures have hardware support for
32x32-bit multiply and so derive no benefit from "simplified"
multipliers.
The few processors that do not (68000, h8/300 and some models of
Microblaze) have arch-specific implementations added. Those
patches are last in the series.
- Overhauls the dcache hash mixing.
The patch in commit 0fed3ac866ea ("namei: Improve hash mixing if
CONFIG_DCACHE_WORD_ACCESS") was an off-the-cuff suggestion.
Replaced with a much more careful design that's simultaneously
faster and better. (My own invention, as there was noting suitable
in the literature I could find. Comments welcome!)
- Modify the hash_name() loop to skip the initial HASH_MIX(). This
would let us salt the hash if we ever wanted to.
- Sort out partial_name_hash().
The hash function is declared as using a long state, even though
it's truncated to 32 bits at the end and the extra internal state
contributes nothing to the result. And some callers do odd things:
- fs/hfs/string.c only allocates 32 bits of state
- fs/hfsplus/unicode.c uses it to hash 16-bit unicode symbols not bytes
- Modify bytemask_from_count to handle inputs of 1..sizeof(long)
rather than 0..sizeof(long)-1. This would simplify users other
than full_name_hash"
Special thanks to Bruce Fields for testing and finding bugs in v1. (I
learned some humbling lessons about "obviously correct" code.)
On the arch-specific front, the m68k assembly has been tested in a
standalone test harness, I've been in contact with the Microblaze
maintainers who mostly don't care, as the hardware multiplier is never
omitted in real-world applications, and I haven't heard anything from
the H8/300 world"
* 'hash' of git://ftp.sciencehorizons.net/linux:
h8300: Add <asm/hash.h>
microblaze: Add <asm/hash.h>
m68k: Add <asm/hash.h>
<linux/hash.h>: Add support for architecture-specific functions
fs/namei.c: Improve dcache hash function
Eliminate bad hash multipliers from hash_32() and hash_64()
Change hash_64() return value to 32 bits
<linux/sunrpc/svcauth.h>: Define hash_str() in terms of hashlen_string()
fs/namei.c: Add hashlen_string() function
Pull out string hash to <linux/stringhash.h>
Diffstat (limited to 'drivers/media')
-rw-r--r-- | drivers/media/usb/dvb-usb-v2/af9015.c | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/drivers/media/usb/dvb-usb-v2/af9015.c b/drivers/media/usb/dvb-usb-v2/af9015.c index 95a7388e89d4..09e0f58f6bb7 100644 --- a/drivers/media/usb/dvb-usb-v2/af9015.c +++ b/drivers/media/usb/dvb-usb-v2/af9015.c @@ -398,6 +398,8 @@ error: } #define AF9015_EEPROM_SIZE 256 +/* 2^31 + 2^29 - 2^25 + 2^22 - 2^19 - 2^16 + 1 */ +#define GOLDEN_RATIO_PRIME_32 0x9e370001UL /* hash (and dump) eeprom */ static int af9015_eeprom_hash(struct dvb_usb_device *d) |