From 4550718f6c75c9abe8b987fa4c625fd041aa95a2 Mon Sep 17 00:00:00 2001 From: Grant Grundler Date: Tue, 10 Oct 2006 14:42:51 -0700 Subject: USB: input: extract() and implement() are bit field manipulation routines extract() and implement() have brain damaged attempts to handle 32-bit wide "fields". The problem is the index math in the original code didn't clear all the relevant bits. (offset >> 5) only compensated for 32-bit index. We need (offset >> 6) if we want to use 64-bit loads. But it was also wrong in that it tried to use quasi-aligned loads. Ie "report" was only incremented in multiples of 4 bytes and then the offset was masked off for values greater than 4 bytes. The right way is to pretend "report" points at a byte array. And offset is then only minor adjustment for < 8 bits of offset. "n" (field width) can then be as big as 24 (assuming 32-bit loads) since "offset" will never be bigger than 7. If someone needs either function to handle more than 24-bits, please document why - point at a specification or specific USB hid device - in comments in the code. extract/implement() are also an eyesore to read. Please banish whoever wrote it to read CodingStyle 3 times in a row to a classroom full of 1st graders armed with rubberbands. Or just flame them. Whatever. Globbing all the code together on two lines does NOT make it faster and is Just Wrong. I've tested this patch on j6000 (dual 750Mhz PA-RISC, 32-bit 2.6.12-rc5). Kyle McMartin tested on c3000 (up 400Mhz PA-RISC, same kernel). "p2-mate" (Peter De Schrijver?) tested on sb1250 (dual core Mips, broadcom "swarm" eval board). Signed-off-by: Grant Grundler Signed-off-by: Matthew Wilcox Cc: Vojtech Pavlik Cc: Dmitry Torokhov Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman --- drivers/usb/input/hid-core.c | 24 +++++++++++++++++------- 1 file changed, 17 insertions(+), 7 deletions(-) diff --git a/drivers/usb/input/hid-core.c b/drivers/usb/input/hid-core.c index a6738a83ff5b1..feabda73a6f9c 100644 --- a/drivers/usb/input/hid-core.c +++ b/drivers/usb/input/hid-core.c @@ -750,21 +750,31 @@ static __inline__ __u32 s32ton(__s32 value, unsigned n) } /* - * Extract/implement a data field from/to a report. + * Extract/implement a data field from/to a little endian report (bit array). */ static __inline__ __u32 extract(__u8 *report, unsigned offset, unsigned n) { - report += (offset >> 5) << 2; offset &= 31; - return (le64_to_cpu(get_unaligned((__le64*)report)) >> offset) & ((1ULL << n) - 1); + u32 x; + + report += offset >> 3; /* adjust byte index */ + offset &= 8 - 1; + x = get_unaligned((u32 *) report); + x = le32_to_cpu(x); + x = (x >> offset) & ((1 << n) - 1); + return x; } static __inline__ void implement(__u8 *report, unsigned offset, unsigned n, __u32 value) { - report += (offset >> 5) << 2; offset &= 31; - put_unaligned((get_unaligned((__le64*)report) - & cpu_to_le64(~((((__u64) 1 << n) - 1) << offset))) - | cpu_to_le64((__u64)value << offset), (__le64*)report); + u32 x; + + report += offset >> 3; + offset &= 8 - 1; + x = get_unaligned((u32 *)report); + x &= cpu_to_le32(~((((__u32) 1 << n) - 1) << offset)); + x |= cpu_to_le32(value << offset); + put_unaligned(x,(u32 *)report); } /* -- cgit 1.2.3-korg