[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
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