Re: [PATCH 2/4] lib: port CRC16 implementation from Linux

[Marco Felsch <m.felsch@pengutronix.de>]

On 25-10-20, Sascha Hauer wrote:
> On Fri, Oct 17, 2025 at 02:03:34PM +0200, Marco Felsch wrote:
> > Port the Linux CRC16 implementation.
> > 
> > Signed-off-by: Marco Felsch <m.felsch@pengutronix.de>
> 
> I was faster ;)

Argh.. :)

> We already have this in master

Thanks for the hint :)

Regards,
  Marco

> 
> Sascha
> 
> > ---
> >  include/linux/crc16.h | 28 +++++++++++++++++++
> >  lib/Kconfig           |  8 ++++++
> >  lib/Makefile          |  1 +
> >  lib/crc16.c           | 65 +++++++++++++++++++++++++++++++++++++++++++
> >  4 files changed, 102 insertions(+)
> >  create mode 100644 include/linux/crc16.h
> >  create mode 100644 lib/crc16.c
> > 
> > diff --git a/include/linux/crc16.h b/include/linux/crc16.h
> > new file mode 100644
> > index 000000000000..9fa74529b317
> > --- /dev/null
> > +++ b/include/linux/crc16.h
> > @@ -0,0 +1,28 @@
> > +/* SPDX-License-Identifier: GPL-2.0-only */
> > +/*
> > + *	crc16.h - CRC-16 routine
> > + *
> > + * Implements the standard CRC-16:
> > + *   Width 16
> > + *   Poly  0x8005 (x^16 + x^15 + x^2 + 1)
> > + *   Init  0
> > + *
> > + * Copyright (c) 2005 Ben Gardner <bgardner@wabtec.com>
> > + */
> > +
> > +#ifndef __CRC16_H
> > +#define __CRC16_H
> > +
> > +#include <linux/types.h>
> > +
> > +extern u16 const crc16_table[256];
> > +
> > +extern u16 crc16(u16 crc, const u8 *buffer, size_t len);
> > +
> > +static inline u16 crc16_byte(u16 crc, const u8 data)
> > +{
> > +	return (crc >> 8) ^ crc16_table[(crc ^ data) & 0xff];
> > +}
> > +
> > +#endif /* __CRC16_H */
> > +
> > diff --git a/lib/Kconfig b/lib/Kconfig
> > index d07e2f3b6959..153a07ec8f4d 100644
> > --- a/lib/Kconfig
> > +++ b/lib/Kconfig
> > @@ -155,6 +155,14 @@ config CRC_CCITT
> >  	  the kernel tree does. Such modules that use library CRC-CCITT
> >  	  functions require M here.
> >  
> > +config CRC16
> > +	tristate "CRC16 functions"
> > +	help
> > +	  This option is provided for the case where no in-kernel-tree
> > +	  modules require CRC16 functions, but a module built outside
> > +	  the kernel tree does. Such modules that use library CRC16
> > +	  functions require M here.
> > +
> >  config CRC8
> >  	bool "CRC8 function"
> >  	help
> > diff --git a/lib/Makefile b/lib/Makefile
> > index 13f1de142008..e9f152b21dad 100644
> > --- a/lib/Makefile
> > +++ b/lib/Makefile
> > @@ -85,6 +85,7 @@ obj-y			+= parseopt.o
> >  obj-y			+= clz_ctz.o
> >  obj-$(CONFIG_CRC_CCITT) += crc-ccitt.o
> >  obj-$(CONFIG_CRC8)	+= crc8.o
> > +obj-$(CONFIG_CRC16)	+= crc16.o
> >  obj-$(CONFIG_NLS)	+= nls_base.o
> >  obj-$(CONFIG_FSL_QE_FIRMWARE) += fsl-qe-firmware.o
> >  obj-$(CONFIG_UBSAN_STANDALONE)	+= ubsan.o
> > diff --git a/lib/crc16.c b/lib/crc16.c
> > new file mode 100644
> > index 000000000000..5c3a803c01e0
> > --- /dev/null
> > +++ b/lib/crc16.c
> > @@ -0,0 +1,65 @@
> > +// SPDX-License-Identifier: GPL-2.0-only
> > +/*
> > + *      crc16.c
> > + */
> > +
> > +#include <linux/types.h>
> > +#include <linux/module.h>
> > +#include <linux/crc16.h>
> > +
> > +/** CRC table for the CRC-16. The poly is 0x8005 (x^16 + x^15 + x^2 + 1) */
> > +u16 const crc16_table[256] = {
> > +	0x0000, 0xC0C1, 0xC181, 0x0140, 0xC301, 0x03C0, 0x0280, 0xC241,
> > +	0xC601, 0x06C0, 0x0780, 0xC741, 0x0500, 0xC5C1, 0xC481, 0x0440,
> > +	0xCC01, 0x0CC0, 0x0D80, 0xCD41, 0x0F00, 0xCFC1, 0xCE81, 0x0E40,
> > +	0x0A00, 0xCAC1, 0xCB81, 0x0B40, 0xC901, 0x09C0, 0x0880, 0xC841,
> > +	0xD801, 0x18C0, 0x1980, 0xD941, 0x1B00, 0xDBC1, 0xDA81, 0x1A40,
> > +	0x1E00, 0xDEC1, 0xDF81, 0x1F40, 0xDD01, 0x1DC0, 0x1C80, 0xDC41,
> > +	0x1400, 0xD4C1, 0xD581, 0x1540, 0xD701, 0x17C0, 0x1680, 0xD641,
> > +	0xD201, 0x12C0, 0x1380, 0xD341, 0x1100, 0xD1C1, 0xD081, 0x1040,
> > +	0xF001, 0x30C0, 0x3180, 0xF141, 0x3300, 0xF3C1, 0xF281, 0x3240,
> > +	0x3600, 0xF6C1, 0xF781, 0x3740, 0xF501, 0x35C0, 0x3480, 0xF441,
> > +	0x3C00, 0xFCC1, 0xFD81, 0x3D40, 0xFF01, 0x3FC0, 0x3E80, 0xFE41,
> > +	0xFA01, 0x3AC0, 0x3B80, 0xFB41, 0x3900, 0xF9C1, 0xF881, 0x3840,
> > +	0x2800, 0xE8C1, 0xE981, 0x2940, 0xEB01, 0x2BC0, 0x2A80, 0xEA41,
> > +	0xEE01, 0x2EC0, 0x2F80, 0xEF41, 0x2D00, 0xEDC1, 0xEC81, 0x2C40,
> > +	0xE401, 0x24C0, 0x2580, 0xE541, 0x2700, 0xE7C1, 0xE681, 0x2640,
> > +	0x2200, 0xE2C1, 0xE381, 0x2340, 0xE101, 0x21C0, 0x2080, 0xE041,
> > +	0xA001, 0x60C0, 0x6180, 0xA141, 0x6300, 0xA3C1, 0xA281, 0x6240,
> > +	0x6600, 0xA6C1, 0xA781, 0x6740, 0xA501, 0x65C0, 0x6480, 0xA441,
> > +	0x6C00, 0xACC1, 0xAD81, 0x6D40, 0xAF01, 0x6FC0, 0x6E80, 0xAE41,
> > +	0xAA01, 0x6AC0, 0x6B80, 0xAB41, 0x6900, 0xA9C1, 0xA881, 0x6840,
> > +	0x7800, 0xB8C1, 0xB981, 0x7940, 0xBB01, 0x7BC0, 0x7A80, 0xBA41,
> > +	0xBE01, 0x7EC0, 0x7F80, 0xBF41, 0x7D00, 0xBDC1, 0xBC81, 0x7C40,
> > +	0xB401, 0x74C0, 0x7580, 0xB541, 0x7700, 0xB7C1, 0xB681, 0x7640,
> > +	0x7200, 0xB2C1, 0xB381, 0x7340, 0xB101, 0x71C0, 0x7080, 0xB041,
> > +	0x5000, 0x90C1, 0x9181, 0x5140, 0x9301, 0x53C0, 0x5280, 0x9241,
> > +	0x9601, 0x56C0, 0x5780, 0x9741, 0x5500, 0x95C1, 0x9481, 0x5440,
> > +	0x9C01, 0x5CC0, 0x5D80, 0x9D41, 0x5F00, 0x9FC1, 0x9E81, 0x5E40,
> > +	0x5A00, 0x9AC1, 0x9B81, 0x5B40, 0x9901, 0x59C0, 0x5880, 0x9841,
> > +	0x8801, 0x48C0, 0x4980, 0x8941, 0x4B00, 0x8BC1, 0x8A81, 0x4A40,
> > +	0x4E00, 0x8EC1, 0x8F81, 0x4F40, 0x8D01, 0x4DC0, 0x4C80, 0x8C41,
> > +	0x4400, 0x84C1, 0x8581, 0x4540, 0x8701, 0x47C0, 0x4680, 0x8641,
> > +	0x8201, 0x42C0, 0x4380, 0x8341, 0x4100, 0x81C1, 0x8081, 0x4040
> > +};
> > +EXPORT_SYMBOL(crc16_table);
> > +
> > +/**
> > + * crc16 - compute the CRC-16 for the data buffer
> > + * @crc:	previous CRC value
> > + * @buffer:	data pointer
> > + * @len:	number of bytes in the buffer
> > + *
> > + * Returns the updated CRC value.
> > + */
> > +u16 crc16(u16 crc, u8 const *buffer, size_t len)
> > +{
> > +	while (len--)
> > +		crc = crc16_byte(crc, *buffer++);
> > +	return crc;
> > +}
> > +EXPORT_SYMBOL(crc16);
> > +
> > +MODULE_DESCRIPTION("CRC16 calculations");
> > +MODULE_LICENSE("GPL");
> > +
> > -- 
> > 2.47.3
> > 
> > 
> > 
> 
> -- 
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