minix/kernel/system/do_segctl.c
2010-04-01 22:22:33 +00:00

55 lines
1.7 KiB
C

/* The kernel call implemented in this file:
* m_type: SYS_SEGCTL
*
* The parameters for this kernel call are:
* m4_l3: SEG_PHYS (physical base address)
* m4_l4: SEG_SIZE (size of segment)
* m4_l1: SEG_SELECT (return segment selector here)
* m4_l2: SEG_OFFSET (return offset within segment here)
* m4_l5: SEG_INDEX (return index into remote memory map here)
*/
#include "kernel/system.h"
#if USE_SEGCTL
/*===========================================================================*
* do_segctl *
*===========================================================================*/
PUBLIC int do_segctl(struct proc * caller, message * m_ptr)
{
/* Return a segment selector and offset that can be used to reach a physical
* address, for use by a driver doing memory I/O in the A0000 - DFFFF range.
*/
u32_t selector;
vir_bytes offset;
int i, index;
phys_bytes phys = (phys_bytes) m_ptr->SEG_PHYS;
vir_bytes size = (vir_bytes) m_ptr->SEG_SIZE;
int result;
/* First check if there is a slot available for this segment. */
index = -1;
for (i=0; i < NR_REMOTE_SEGS; i++) {
if (! caller->p_priv->s_farmem[i].in_use) {
index = i;
caller->p_priv->s_farmem[i].in_use = TRUE;
caller->p_priv->s_farmem[i].mem_phys = phys;
caller->p_priv->s_farmem[i].mem_len = size;
break;
}
}
if (index < 0) return(ENOSPC);
offset = alloc_remote_segment(&selector, &caller->p_seg,
i, phys, size, USER_PRIVILEGE);
result = OK;
/* Request successfully done. Now return the result. */
m_ptr->SEG_INDEX = index | REMOTE_SEG;
m_ptr->SEG_SELECT = selector;
m_ptr->SEG_OFFSET = offset;
return(result);
}
#endif /* USE_SEGCTL */