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Commit 95d1c895 authored by Dmitry Torokhov's avatar Dmitry Torokhov Committed by Jiri Kosina
Browse files

HID: simplify implement() a bit 



The 'size' variable is not really needed, and we can also shift constant
in the loop body when masking off existing bits.

Also we do not have to use 64 bit calculations if we take an extra
branch.

[jkosina@suse.cz: fix a small error in changelog]
Suggested-by: default avatarDoug Anderson <dianders@chromium.org>
Signed-off-by: default avatarDmitry Torokhov <dmitry.torokhov@gmail.com>
Reviewed-by: default avatarDouglas Anderson <dianders@chromium.org>
Signed-off-by: default avatarJiri Kosina <jkosina@suse.cz>
parent 6edac6fd

drivers/hid/hid-core.c

+15 −18
Original line number Diff line number Diff line
@@ -1129,48 +1129,45 @@ EXPORT_SYMBOL_GPL(hid_field_extract); 
static void __implement(u8 *report, unsigned offset, int n, u32 value)

{

	unsigned int idx = offset / 8;

	unsigned int size = offset + n;

	unsigned int bit_shift = offset % 8;

	int bits_to_set = 8 - bit_shift;

	u8 bit_mask = 0xff << bit_shift;



	while (n - bits_to_set >= 0) {

		report[idx] &= ~bit_mask;

		report[idx] &= ~(0xff << bit_shift);

		report[idx] |= value << bit_shift;

		value >>= bits_to_set;

		n -= bits_to_set;

		bits_to_set = 8;

		bit_mask = 0xff;

		bit_shift = 0;

		idx++;

	}



	/* last nibble */

	if (n) {

		if (size % 8)

			bit_mask &= (1U << (size % 8)) - 1;

		report[idx] &= ~bit_mask;

		report[idx] |= (value << bit_shift) & bit_mask;

		u8 bit_mask = ((1U << n) - 1);

		report[idx] &= ~(bit_mask << bit_shift);

		report[idx] |= value << bit_shift;

	}

}



static void implement(const struct hid_device *hid, u8 *report,

		      unsigned offset, unsigned n, u32 value)

{

	u64 m;



	if (n > 32) {

	if (unlikely(n > 32)) {

		hid_warn(hid, "%s() called with n (%d) > 32! (%s)\n",

			 __func__, n, current->comm);

		n = 32;

	}



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

	if (value > m)

		hid_warn(hid, "%s() called with too large value %d! (%s)\n",

			 __func__, value, current->comm);

	WARN_ON(value > m);

	} else if (n < 32) {

		u32 m = (1U << n) - 1;



		if (unlikely(value > m)) {

			hid_warn(hid,

				 "%s() called with too large value %d (n: %d)! (%s)\n",

				 __func__, value, n, current->comm);

			WARN_ON(1);

			value &= m;

		}

	}



	__implement(report, offset, n, value);

}