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cq_desc.h
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1 /*
2  * Copyright 2008 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 #ifndef _CQ_DESC_H_
19 #define _CQ_DESC_H_
20 
21 /*
22  * Completion queue descriptor types
23  */
30 };
31 
32 /* Completion queue descriptor: 16B
33  *
34  * All completion queues have this basic layout. The
35  * type_specfic area is unique for each completion
36  * queue type.
37  */
38 struct cq_desc {
41  u8 type_specfic[11];
42  u8 type_color;
43 };
44 
45 #define CQ_DESC_TYPE_BITS 4
46 #define CQ_DESC_TYPE_MASK ((1 << CQ_DESC_TYPE_BITS) - 1)
47 #define CQ_DESC_COLOR_MASK 1
48 #define CQ_DESC_COLOR_SHIFT 7
49 #define CQ_DESC_Q_NUM_BITS 10
50 #define CQ_DESC_Q_NUM_MASK ((1 << CQ_DESC_Q_NUM_BITS) - 1)
51 #define CQ_DESC_COMP_NDX_BITS 12
52 #define CQ_DESC_COMP_NDX_MASK ((1 << CQ_DESC_COMP_NDX_BITS) - 1)
53 
54 static inline void cq_desc_dec(const struct cq_desc *desc_arg,
55  u8 *type, u8 *color, u16 *q_number, u16 *completed_index)
56 {
57  const struct cq_desc *desc = desc_arg;
58  const u8 type_color = desc->type_color;
59 
60  *color = (type_color >> CQ_DESC_COLOR_SHIFT) & CQ_DESC_COLOR_MASK;
61 
62  /*
63  * Make sure color bit is read from desc *before* other fields
64  * are read from desc. Hardware guarantees color bit is last
65  * bit (byte) written. Adding the rmb() prevents the compiler
66  * and/or CPU from reordering the reads which would potentially
67  * result in reading stale values.
68  */
69 
70  rmb();
71 
72  *type = type_color & CQ_DESC_TYPE_MASK;
73  *q_number = le16_to_cpu(desc->q_number) & CQ_DESC_Q_NUM_MASK;
74  *completed_index = le16_to_cpu(desc->completed_index) &
76 }
77 
78 #endif /* _CQ_DESC_H_ */