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cq_desc.h
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1 /*
2  * Copyright 2008-2010 Cisco Systems, Inc. All rights reserved.
3  * Copyright 2007 Nuova Systems, Inc. All rights reserved.
4  *
5  * This program is free software; you may redistribute it and/or modify
6  * it under the terms of the GNU General Public License as published by
7  * the Free Software Foundation; version 2 of the License.
8  *
9  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
10  * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
11  * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
12  * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
13  * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
14  * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
15  * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
16  * SOFTWARE.
17  *
18  */
19 
20 #ifndef _CQ_DESC_H_
21 #define _CQ_DESC_H_
22 
23 /*
24  * Completion queue descriptor types
25  */
32 };
33 
34 /* Completion queue descriptor: 16B
35  *
36  * All completion queues have this basic layout. The
37  * type_specfic area is unique for each completion
38  * queue type.
39  */
40 struct cq_desc {
45 };
46 
47 #define CQ_DESC_TYPE_BITS 4
48 #define CQ_DESC_TYPE_MASK ((1 << CQ_DESC_TYPE_BITS) - 1)
49 #define CQ_DESC_COLOR_MASK 1
50 #define CQ_DESC_COLOR_SHIFT 7
51 #define CQ_DESC_Q_NUM_BITS 10
52 #define CQ_DESC_Q_NUM_MASK ((1 << CQ_DESC_Q_NUM_BITS) - 1)
53 #define CQ_DESC_COMP_NDX_BITS 12
54 #define CQ_DESC_COMP_NDX_MASK ((1 << CQ_DESC_COMP_NDX_BITS) - 1)
55 
56 static inline void cq_desc_dec(const struct cq_desc *desc_arg,
57  u8 *type, u8 *color, u16 *q_number, u16 *completed_index)
58 {
59  const struct cq_desc *desc = desc_arg;
60  const u8 type_color = desc->type_color;
61 
62  *color = (type_color >> CQ_DESC_COLOR_SHIFT) & CQ_DESC_COLOR_MASK;
63 
64  /*
65  * Make sure color bit is read from desc *before* other fields
66  * are read from desc. Hardware guarantees color bit is last
67  * bit (byte) written. Adding the rmb() prevents the compiler
68  * and/or CPU from reordering the reads which would potentially
69  * result in reading stale values.
70  */
71 
72  rmb();
73 
74  *type = type_color & CQ_DESC_TYPE_MASK;
75  *q_number = le16_to_cpu(desc->q_number) & CQ_DESC_Q_NUM_MASK;
76  *completed_index = le16_to_cpu(desc->completed_index) &
78 }
79 
80 #endif /* _CQ_DESC_H_ */