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IOPL !!!IOPL NAME SYNOPSIS DESCRIPTION RETURN VALUE ERRORS NOTES FROM THE KERNEL SOURCE CONFORMING TO COMPATIBILITY SEE ALSO ---- !!NAME iopl - change I/O privilege level !!SYNOPSIS __#include __ __int iopl(int__ ''level''__);__ !!DESCRIPTION __iopl__ changes the I/O privilege level of the current process, as specified in ''level''. This call is necessary to allow 8514-compatible X servers to run under Linux. Since these X servers require access to all 65536 I/O ports, the __ioperm__ call is not sufficient. In addition to granting unrestricted I/O port access, running at a higher I/O privilege level also allows the process to disable interrupts. This will probably crash the system, and is not recommended. Permissions are inherited by fork and exec. The I/O privilege level for a normal process is 0. !!RETURN VALUE On success, zero is returned. On error, -1 is returned, and ''errno'' is set appropriately. !!ERRORS __EINVAL__ ''level'' is greater than 3. __EPERM__ The current user is not the super-user. !!NOTES FROM THE KERNEL SOURCE __iopl__ has to be used when you want to access the I/O ports beyond the 0x3ff range: to get the full 65536 ports bitmapped you'd need 8kB of bitmaps/process, which is a bit excessive. !!CONFORMING TO __iopl__ is Linux specific and should not be used in processes intended to be portable. !!COMPATIBILITY Under libc5, the prototype for __iopl__() was given in ''''. !!SEE ALSO ioperm(2) ----
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