Date: Sun, 6 Feb 2005 14:41:09 +0200 From: Peter Pentchev <roam@ringlet.net> To: kamalp@acm.org Cc: freebsd-hackers@freebsd.org Subject: Re: Opening and wriiting to file in Kern Message-ID: <20050206124109.GA29361@straylight.m.ringlet.net> In-Reply-To: <20050206122241.63590.qmail@web52702.mail.yahoo.com> References: <4206008F.2060100@freebsd.org> <20050206122241.63590.qmail@web52702.mail.yahoo.com>
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--ZGiS0Q5IWpPtfppv Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Sun, Feb 06, 2005 at 04:22:41AM -0800, Kamal R. Prasad wrote: >=20 > --- Scott Long <scottl@freebsd.org> wrote: >=20 > > Ashwin Chandra wrote: > >=20 > > > Does anyone know the correct calls to open a file, > > write to it, and close it, IN *kernel* mode.=20 > > >=20 > > > Ash > >=20 > > There is no common API for doing this, which is > > pretty much on purpose.=20 > > First, you need to ask yourself why your task > > needs it done in the=20 > > kernel and not in userland. >=20 > A feature implemented within the kernel that requires > making stuff persistent would almost certainly require > file I/O. For that matter, a kernel (module) that > reads a configuration file will also need the same > facility. I don't see anything wrong with providing a > stream (like) interface to the filesystem. While there might indeed be nothing wrong with it, besides added complexity, the traditional way to do it would be to have a userland configuration utility that communicates with the kernel module either via ioctl's on some standard device, or via ioctl's or reading/writing of a driver-specific device. This has the advantage of being a bit more portable - while different OS's implement disk/file I/O within the kernel in wildly different ways, all OS's provide relatively simple ways for a kernel module to define a new device and handle ioctl's to it, and all OS's provide basically the same userland-to-kernel interface for having a program open a device and issue ioctl's to it :) Another way would be, again, communication between a userland utility and a kernel module, but this time using mmap'd files/devices instead of ioctl's. G'luck, Peter --=20 Peter Pentchev roam@ringlet.net roam@cnsys.bg roam@FreeBSD.org PGP key: http://people.FreeBSD.org/~roam/roam.key.asc Key fingerprint FDBA FD79 C26F 3C51 C95E DF9E ED18 B68D 1619 4553 This sentence was in the past tense. --ZGiS0Q5IWpPtfppv Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.0 (FreeBSD) iD8DBQFCBhBl7Ri2jRYZRVMRAg8PAKCnuRtriq792sCo6XNJ23hAzHSgcwCgoZI2 Tw3DyJDCymoLdFrbnOp0lOw= =0uuZ -----END PGP SIGNATURE----- --ZGiS0Q5IWpPtfppv--
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