drivers/xen/sfc_netutil/accel_shared_fifo.h

   1 /****************************************************************************
   2  * Solarflare driver for Xen network acceleration
   3  *
   4  * Copyright 2006-2008: Solarflare Communications Inc,
   5  *                      9501 Jeronimo Road, Suite 250,
   6  *                      Irvine, CA 92618, USA
   7  *
   8  * Maintained by Solarflare Communications <linux-xen-drivers@solarflare.com>
   9  *
  10  * This program is free software; you can redistribute it and/or modify it
  11  * under the terms of the GNU General Public License version 2 as published
  12  * by the Free Software Foundation, incorporated herein by reference.
  13  *
  14  * This program is distributed in the hope that it will be useful,
  15  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  16  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  17  * GNU General Public License for more details.
  18  *
  19  * You should have received a copy of the GNU General Public License
  20  * along with this program; if not, write to the Free Software
  21  * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
  22  ****************************************************************************
  23  */
  24
  25 #ifndef NET_ACCEL_SHARED_FIFO_H
  26 #define NET_ACCEL_SHARED_FIFO_H
  27
  28 /*
  29  * This is based on fifo.h, but handles sharing between address spaces
  30  * that don't trust each other, by splitting out the read and write
  31  * indices. This costs at least one pointer indirection more than the
  32  * vanilla version per access.
  33  */
  34
  35 typedef struct {
  36         char*    fifo;
  37         unsigned      fifo_mask;
  38         unsigned      *fifo_rd_i;
  39         unsigned      *fifo_wr_i;
  40 } sh_byte_fifo2;
  41
  42 #define SH_FIFO2_M(f, x)     ((x) & ((f)->fifo_mask))
  43
  44 static inline unsigned log2_ge(unsigned long n, unsigned min_order) {
  45         unsigned order = min_order;
  46         while((1ul << order) < n) ++order;
  47         return order;
  48 }
  49
  50 static inline unsigned long pow2(unsigned order) {
  51         return (1ul << order);
  52 }
  53
  54 #define is_pow2(x)  (pow2(log2_ge((x), 0)) == (x))
  55
  56 #define sh_fifo2_valid(f)  ((f) && (f)->fifo && (f)->fifo_mask > 0 &&   \
  57                             is_pow2((f)->fifo_mask+1u))
  58
  59 #define sh_fifo2_init(f, cap, _rptr, _wptr)             \
  60         do {                                            \
  61                 BUG_ON(!is_pow2((cap) + 1));            \
  62                 (f)->fifo_rd_i = _rptr;                 \
  63                 (f)->fifo_wr_i = _wptr;                 \
  64                 *(f)->fifo_rd_i = *(f)->fifo_wr_i = 0u; \
  65                 (f)->fifo_mask = (cap);                 \
  66         } while(0)
  67
  68 #define sh_fifo2_num(f)      SH_FIFO2_M((f),*(f)->fifo_wr_i - *(f)->fifo_rd_i)
  69 #define sh_fifo2_space(f)    SH_FIFO2_M((f),*(f)->fifo_rd_i - *(f)->fifo_wr_i-1u)
  70 #define sh_fifo2_is_empty(f)  (sh_fifo2_num(f)==0)
  71 #define sh_fifo2_not_empty(f) (sh_fifo2_num(f)!=0)
  72 #define sh_fifo2_is_full(f)   (sh_fifo2_space(f)==0u)
  73 #define sh_fifo2_not_full(f)  (sh_fifo2_space(f)!=0u)
  74 #define sh_fifo2_buf_size(f) ((f)->fifo_mask + 1u)
  75 #define sh_fifo2_capacity(f) ((f)->fifo_mask)
  76 #define sh_fifo2_end(f)      ((f)->fifo + sh_fifo2_buf_size(f))
  77 #define sh_fifo2_not_half_full(f) (sh_fifo2_space(f) > (sh_fifo2_capacity(f) >> 1))
  78
  79 #define sh_fifo2_peek(f)     ((f)->fifo[SH_FIFO2_M((f), *(f)->fifo_rd_i)])
  80 #define sh_fifo2_peekp(f)    ((f)->fifo + SH_FIFO2_M((f), *(f)->fifo_rd_i))
  81 #define sh_fifo2_poke(f)     ((f)->fifo[SH_FIFO2_M((f), *(f)->fifo_wr_i)])
  82 #define sh_fifo2_pokep(f)    ((f)->fifo + SH_FIFO2_M((f), *(f)->fifo_wr_i))
  83 #define sh_fifo2_peek_i(f,i) ((f)->fifo[SH_FIFO2_M((f), *(f)->fifo_rd_i+(i))])
  84 #define sh_fifo2_poke_i(f,i) ((f)->fifo[SH_FIFO2_M((f), *(f)->fifo_wr_i+(i))])
  85
  86 #define sh_fifo2_rd_next(f)                                     \
  87         do {*(f)->fifo_rd_i = *(f)->fifo_rd_i + 1u;} while(0)
  88 #define sh_fifo2_wr_next(f)                                     \
  89         do {*(f)->fifo_wr_i = *(f)->fifo_wr_i + 1u;} while(0)
  90 #define sh_fifo2_rd_adv(f, n)                                   \
  91         do {*(f)->fifo_rd_i = *(f)->fifo_rd_i + (n);} while(0)
  92 #define sh_fifo2_wr_adv(f, n)                                   \
  93         do {*(f)->fifo_wr_i = *(f)->fifo_wr_i + (n);} while(0)
  94
  95 #define sh_fifo2_put(f, v)                                              \
  96         do {sh_fifo2_poke(f) = (v); wmb(); sh_fifo2_wr_next(f);} while(0)
  97
  98 #define sh_fifo2_get(f, pv)                                             \
  99         do {*(pv) = sh_fifo2_peek(f); mb(); sh_fifo2_rd_next(f);} while(0)
 100
 101 static inline unsigned sh_fifo2_contig_num(sh_byte_fifo2 *f)
 102 {
 103         unsigned fifo_wr_i = SH_FIFO2_M(f, *f->fifo_wr_i);
 104         unsigned fifo_rd_i = SH_FIFO2_M(f, *f->fifo_rd_i);
 105
 106         return (fifo_wr_i >= fifo_rd_i)
 107                 ? fifo_wr_i - fifo_rd_i
 108                 : f->fifo_mask + 1u - *(f)->fifo_rd_i;
 109 }
 110
 111 static inline unsigned sh_fifo2_contig_space(sh_byte_fifo2 *f)
 112 {
 113         unsigned fifo_wr_i = SH_FIFO2_M(f, *f->fifo_wr_i);
 114         unsigned fifo_rd_i = SH_FIFO2_M(f, *f->fifo_rd_i);
 115
 116         return (fifo_rd_i > fifo_wr_i)
 117                 ? fifo_rd_i - fifo_wr_i - 1
 118                 : (f->fifo_mask + 1u - fifo_wr_i
 119                    /*
 120                     * The last byte can't be used if the read pointer
 121                     * is at zero.
 122                     */
 123                    - (fifo_rd_i==0));
 124 }
 125
 126
 127 #endif /* NET_ACCEL_SHARED_FIFO_H */