Commit 68717950 authored by Grant Grundler's avatar Grant Grundler Committed by Greg Kroah-Hartman
Browse files

hid-core: big-endian fix fix 

Adam Kropelin had posted 32-bit fix in June 2005 about two weeks after I
originally had posted my fixes for big endian support.  Adam has a UPS
device which reports LINEV using 32-bits.

Added comments to describe the limitations of the code.

extract() is the same version I posted earlier and tested in user space. 
Made similar changes to implement() routine.  I've written (and will
shortly post) a test for implement().  Code tested on C3600 (parisc) with
USB keyboard/mouse attached.


I've dropped test_implement.c and a few other user space test programs on
http://iou.parisc-linux.org/~grundler/tests/



-rw-r--r-- 1 grundler grundler 1750 Oct 18 09:13 test_extract.c
-rw-r--r-- 1 grundler grundler  561 Jan 25  2006 test_ffs.c
-rw-r--r-- 1 grundler users    7175 Apr  8  2005 test_fls.c
-rw-r--r-- 1 grundler grundler  206 Sep  1 15:52 test_gettimeofday.c
-rw-r--r-- 1 grundler grundler 1886 Oct 19 09:20 test_implement.c
-rw-r--r-- 1 grundler users    2707 Jun  4  2005 test_unaligned.c

I would appreciate if someone else would look at the output of
test_implement.c to make it does The Right Thing.

Signed-off-by: default avatarGrant Grundler <grundler@parisc-linux.org>
Cc: Matthew Wilcox <matthew@wil.cx>
Cc: Dmitry Torokhov <dtor@mail.ru>
Acked-By: default avatarAdam Kropelin <akropel1@rochester.rr.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>
parent bc724b98

drivers/usb/input/hid-core.c

+42 −17
Original line number Diff line number Diff line
@@ -270,7 +270,7 @@ static int hid_add_field(struct hid_parser *parser, unsigned report_type, unsign 
 * Read data value from item.

 */



static __inline__ __u32 item_udata(struct hid_item *item)

static u32 item_udata(struct hid_item *item)

{

	switch (item->size) {

		case 1: return item->data.u8;
@@ -280,7 +280,7 @@ static __inline__ __u32 item_udata(struct hid_item *item) 
	return 0;

}



static __inline__ __s32 item_sdata(struct hid_item *item)

static s32 item_sdata(struct hid_item *item)

{

	switch (item->size) {

		case 1: return item->data.s8;
@@ -727,7 +727,7 @@ static struct hid_device *hid_parse_report(__u8 *start, unsigned size) 
 * done by hand.

 */



static __inline__ __s32 snto32(__u32 value, unsigned n)

static s32 snto32(__u32 value, unsigned n)

{

	switch (n) {

		case 8:  return ((__s8)value);
@@ -741,9 +741,9 @@ static __inline__ __s32 snto32(__u32 value, unsigned n) 
 * Convert a signed 32-bit integer to a signed n-bit integer.

 */



static __inline__ __u32 s32ton(__s32 value, unsigned n)

static u32 s32ton(__s32 value, unsigned n)

{

	__s32 a = value >> (n - 1);

	s32 a = value >> (n - 1);

	if (a && a != -1)

		return value < 0 ? 1 << (n - 1) : (1 << (n - 1)) - 1;

	return value & ((1 << n) - 1);
@@ -751,30 +751,55 @@ static __inline__ __u32 s32ton(__s32 value, unsigned n) 


/*

 * Extract/implement a data field from/to a little endian report (bit array).

 *

 * Code sort-of follows HID spec:

 *     http://www.usb.org/developers/devclass_docs/HID1_11.pdf

 *

 * While the USB HID spec allows unlimited length bit fields in "report

 * descriptors", most devices never use more than 16 bits.

 * One model of UPS is claimed to report "LINEV" as a 32-bit field.

 * Search linux-kernel and linux-usb-devel archives for "hid-core extract".

 */



static __inline__ __u32 extract(__u8 *report, unsigned offset, unsigned n)

{

	u32 x;

	u64 x;



	WARN_ON(n > 32);



	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;

	offset &= 7;		/* now only need bit offset into one byte */

	x = get_unaligned((u64 *) report);

	x = le64_to_cpu(x);

	x = (x >> offset) & ((1ULL << n) - 1);	/* extract bit field */

	return (u32) x;

}



/*

 * "implement" : set bits in a little endian bit stream.

 * Same concepts as "extract" (see comments above).

 * The data mangled in the bit stream remains in little endian

 * order the whole time. It make more sense to talk about

 * endianness of register values by considering a register

 * a "cached" copy of the little endiad bit stream.

 */

static __inline__ void implement(__u8 *report, unsigned offset, unsigned n, __u32 value)

{

	u32 x;

	u64 x;

	u64 m = (1ULL << n) - 1;



	WARN_ON(n > 32);



	WARN_ON(value > m);

	value &= m;



	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);

	offset &= 7;



	x = get_unaligned((u64 *)report);

	x &= cpu_to_le64(~(m << offset));

	x |= cpu_to_le64(((u64) value) << offset);

	put_unaligned(x, (u64 *) report);

}



/*

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