linux-kernel - Re: [PATCH] driver: char: bfin_crc: CRC hardware accelerator driver for BF60x family processors.

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Message-Id: <201205161339.41736.arnd@arndb.de>
Date:	Wed, 16 May 2012 13:39:41 +0000
From:	Arnd Bergmann <arnd@...db.de>
To:	"Greg Kroah-Hartman" <gregkh@...uxfoundation.org>
Cc:	sonic.zhang@...log.com, LKML <linux-kernel@...r.kernel.org>,
	uclinux-dist-devel@...ckfin.uclinux.org
Subject: Re: [PATCH] driver: char: bfin_crc: CRC hardware accelerator driver for BF60x family processors.

On Wednesday 16 May 2012, Greg Kroah-Hartman wrote:
> On Wed, May 16, 2012 at 04:26:07PM +0800, sonic.zhang@...log.com wrote:
> > From: Sonic Zhang <sonic.zhang@...log.com>
> > 
> > The CRC peripheral is a hardware block used to compute the CRC of the block
> > of data. This is based on a CRC32 engine which computes the CRC value of 32b
> > data words presented to it. For data words of < 32b in size, it is the
> > responsibility of the application to pack the data into 32b data units.
> > 
> > This driver defines data strcture crc_info and 4 IOCTL interfaces for applciations.
> > 1) CRC Memory Scan
> > 2) CRC Memory Transfer
> > 3) CRC Data Verify
> > 4) CRC Data Fill
> > 
> > Signed-off-by: Sonic Zhang <sonic.zhang@...log.com>
> > ---
> >  drivers/char/Kconfig    |    8 +
> >  drivers/char/Makefile   |    1 +
> >  drivers/char/bfin_crc.c |  537 +++++++++++++++++++++++++++++++++++++++++++++++
> >  3 files changed, 546 insertions(+), 0 deletions(-)
> >  create mode 100644 drivers/char/bfin_crc.c
> 
> Why is this a char driver, and not a crypto driver, using the existing
> crypto userspace api for things like this?

Do we have a userspace crypto API these days? The last I remember every
attempt to add one so far was abandoned before it got merged. There is
drivers/s390/crypto/zcrypt*, which has a nonportable API, and 
then there is the in-kernel crypto layer in drivers/crypto that has
no user interface at all.

I agree that having another private driver for bfin_crc is not a good
idea, but I also don't have a better one.

About the driver itself, the submission seems incomplete (missing at
least the bfin_crc.h file) and the driver has a number of shortcomings
that we should discuss in case we decide to merge it.

	Arnd
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