Date: Sat, 10 Jun 2000 10:40:03 +0930 From: Greg Lehey <grog@lemis.com> To: "NandaKumar P.K." <p_k_nandan@yahoo.com> Cc: FreeBSD Hackers <hackers@freebsd.org> Subject: Re: IOCTL to the character driver is failing Message-ID: <20000610104003.B81728@wantadilla.lemis.com> In-Reply-To: <20000609072804.27088.qmail@web1903.mail.yahoo.com> References: <20000609072804.27088.qmail@web1903.mail.yahoo.com>
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[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<<PAGE_SHIFT) /* bytes/page */ Even that is probably too big. What are you trying to transfer that's so big? Greg -- When replying to this message, please copy the original recipients. For more information, see http://www.lemis.com/questions.html Finger grog@lemis.com for PGP public key See complete headers for address and phone numbers To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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