include/linux/packing.h

   1 /* SPDX-License-Identifier: BSD-3-Clause
   2  * Copyright (c) 2016-2018, NXP Semiconductors
   3  * Copyright (c) 2018-2019, Vladimir Oltean <olteanv@gmail.com>
   4  */
   5 #ifndef _LINUX_PACKING_H
   6 #define _LINUX_PACKING_H
   7
   8 #include <linux/types.h>
   9 #include <linux/bitops.h>
  10
  11 #define QUIRK_MSB_ON_THE_RIGHT  BIT(0)
  12 #define QUIRK_LITTLE_ENDIAN     BIT(1)
  13 #define QUIRK_LSW32_IS_FIRST    BIT(2)
  14
  15 enum packing_op {
  16         PACK,
  17         UNPACK,
  18 };
  19
  20 /**
  21  * packing - Convert numbers (currently u64) between a packed and an unpacked
  22  *           format. Unpacked means laid out in memory in the CPU's native
  23  *           understanding of integers, while packed means anything else that
  24  *           requires translation.
  25  *
  26  * @pbuf: Pointer to a buffer holding the packed value.
  27  * @uval: Pointer to an u64 holding the unpacked value.
  28  * @startbit: The index (in logical notation, compensated for quirks) where
  29  *            the packed value starts within pbuf. Must be larger than, or
  30  *            equal to, endbit.
  31  * @endbit: The index (in logical notation, compensated for quirks) where
  32  *          the packed value ends within pbuf. Must be smaller than, or equal
  33  *          to, startbit.
  34  * @op: If PACK, then uval will be treated as const pointer and copied (packed)
  35  *      into pbuf, between startbit and endbit.
  36  *      If UNPACK, then pbuf will be treated as const pointer and the logical
  37  *      value between startbit and endbit will be copied (unpacked) to uval.
  38  * @quirks: A bit mask of QUIRK_LITTLE_ENDIAN, QUIRK_LSW32_IS_FIRST and
  39  *          QUIRK_MSB_ON_THE_RIGHT.
  40  *
  41  * Return: 0 on success, EINVAL or ERANGE if called incorrectly. Assuming
  42  *         correct usage, return code may be discarded.
  43  *         If op is PACK, pbuf is modified.
  44  *         If op is UNPACK, uval is modified.
  45  */
  46 int packing(void *pbuf, u64 *uval, int startbit, int endbit, size_t pbuflen,
  47             enum packing_op op, u8 quirks);
  48
  49 #endif