1<h2>memory_object_data_request</h2>
2<hr>
3<p>
4<strong>Server Interface</strong> - Request that memory manager page-in specified data.
5<h3>SYNOPSIS</h3>
6<pre>
7<strong>kern_return_t   memory_object_data_request</strong>
8                <strong>(memory_object_t</strong>                  <var>memory_object</var>,
9                 <strong>memory_object_control_t</strong>         <var>memory_control</var>,
10                 <strong>vm_offset_t</strong>                             <var>offset</var>,
11                 <strong>vm_size_t</strong>                               <var>length</var>,
12                 <strong>vm_prot_t</strong>                       <var>desired_access</var><strong>);</strong>
13
14
15<strong>kern_return_t   seqnos_memory_object_data_request</strong>
16                <strong>(memory_object_t</strong>                  <var>memory_object</var>,
17                 <strong>mach_port_seqno_t</strong>                        <var>seqno</var>,
18                 <strong>memory_object_control_t</strong>         <var>memory_control</var>,
19                 <strong>vm_offset_t</strong>                             <var>offset</var>,
20                 <strong>vm_size_t</strong>                               <var>length</var>,
21                 <strong>vm_prot_t</strong>                       <var>desired_access</var><strong>);</strong>
22</pre>
23<h3>PARAMETERS</h3>
24<dl>
25<p>
26<dt> <var>memory_object</var> 
27<dd>
28[in abstract-memory-object (receive) right]
29The abstract memory
30object port that represents the memory object data.
31<p>
32<dt> <var>seqno</var> 
33<dd>
34[in scalar]
35The sequence number of this message relative to the abstract 
36memory object port.
37<p>
38<dt> <var>memory_control</var> 
39<dd>
40[in memory-cache-control send right]
41The memory cache control port 
42to be used for a response by the memory manager.  If the memory
43object has been supplied to more than one kernel, this parameter
44identifies the kernel that is making the call.
45<p>
46<dt> <var>offset</var> 
47<dd>
48[in scalar]
49The offset within the memory object.
50<p>
51<dt> <var>length</var> 
52<dd>
53[in scalar]
54The number of bytes requested, starting at <var>offset</var>.  The
55number converts to an integral number of virtual pages.
56<p>
57<dt> <var>desired_access</var> 
58<dd>
59[in scalar]
60The memory access modes to be allowed for the cached 
61data.  Possible values are obtained by or'ing together the following
62values:
63<dl>
64<p>
65<dt> <strong>VM_PROT_READ</strong>
66<dd>
67Allows read access.
68<p>
69<dt> <strong>VM_PROT_WRITE</strong>
70<dd>
71Allows write access.
72<p>
73<dt> <strong>VM_PROT_EXECUTE</strong>
74<dd>
75Allows execute access.
76</dl>
77</dl>
78<h3>DESCRIPTION</h3>
79<p>
80A <strong>memory_object_data_request</strong> function is called as
81the result of a kernel 
82message requesting data from the specified memory object, for at least the
83access specified.
84<p>
85The kernel issues this call after a cache miss (that is, a page
86fault for which the 
87kernel does not have the data).  The kernel requests only amounts
88of data that are 
89multiples of the page size included in the
90<strong>memory_object_init</strong> or <strong>memory_object_create</strong> call.
91<p>
92The memory manager is expected to use <strong>memory_object_data_supply</strong> to
93return at least the specified data, with as much access as it
94can allow.  If the
95memory manager cannot provide the data (for example, because
96of a hardware error), 
97it can use the <strong>memory_object_data_error</strong> call.  The
98memory manager can also 
99use <strong>memory_object_data_unavailable</strong> to tell the kernel
100to supply zero-filled 
101memory for the region.
102<h3>RETURN VALUES</h3>
103<p>
104Only generic errors apply.
105<h3>RELATED INFORMATION</h3>
106<p>
107Functions:
108<a href="memory_object_data_error.html"><strong>memory_object_data_error</strong></a>,
109<a href="memory_object_data_supply.html"><strong>memory_object_data_supply</strong></a>,
110<a href="MO_data_unavailable.html"><strong>memory_object_data_unavailable</strong></a>,
111<a href="memory_object_server.html"><strong>memory_object_server</strong></a>,
112<a href="SMO_server.html"><strong>seqnos_memory_object_server</strong></a>.
113
114