From owner-freebsd-hackers Fri Jun 9 22:48:14 2000 Delivered-To: freebsd-hackers@freebsd.org Received: from mass.cdrom.com (adsl-63-206-88-224.dsl.snfc21.pacbell.net [63.206.88.224]) by hub.freebsd.org (Postfix) with ESMTP id 2943637BCB4 for ; Fri, 9 Jun 2000 22:48:12 -0700 (PDT) (envelope-from msmith@mass.cdrom.com) Received: from mass.cdrom.com (localhost [127.0.0.1]) by mass.cdrom.com (8.9.3/8.9.3) with ESMTP id WAA01236; Fri, 9 Jun 2000 22:52:00 -0700 (PDT) (envelope-from msmith@mass.cdrom.com) Message-Id: <200006100552.WAA01236@mass.cdrom.com> X-Mailer: exmh version 2.1.1 10/15/1999 To: Greg Lehey Cc: "NandaKumar P.K." , FreeBSD Hackers Subject: Re: IOCTL to the character driver is failing In-reply-to: Your message of "Sat, 10 Jun 2000 10:40:03 +0930." <20000610104003.B81728@wantadilla.lemis.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Date: Fri, 09 Jun 2000 22:52:00 -0700 From: Mike Smith Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG > [moved to -hackers; this is an in-depth technical question] > > On Friday, 9 June 2000 at 0:28:04 -0700, NandaKumar P.K. wrote: > > Hi, > > > > I am in the process of debugging my character driver > > interface to the RAID controller card. Lots of my > > IOCTLs i sent from the user code works with the driver > > but some IOCTLs are not reaching the driver. I found > > that one of the IOCTL that failed is having a size of > > data as 8096 bytes. Does FreeBSD has got any size > > restriction in IOCTL data size ? I know that there is > > no problem with Linux and Windows NT. > > Indeed, you're limited to 4096 bytes. From sys/ioccom.h: > > #define IOCPARM_MASK 0x1fff /* parameter length, at most 13 bits */ > #define IOCPARM_MAX PAGE_SIZE /* max size of ioctl, mult. of PAGE_SIZE */ > > >From sys/param.h: > > #define PAGE_SHIFT 12 /* LOG2(PAGE_SIZE) */ > #define PAGE_SIZE (1< > Even that is probably too big. What are you trying to transfer that's > so big? NB. if you want to move more than 4k, you should pass a pointer to the buffer in userspace and use copyin/copyout. -- \\ Give a man a fish, and you feed him for a day. \\ Mike Smith \\ Tell him he should learn how to fish himself, \\ msmith@freebsd.org \\ and he'll hate you for a lifetime. \\ msmith@cdrom.com To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message