dma.c

Version: - FREEBSD - FREEBSD-13-STABLE - FREEBSD-13-0 - FREEBSD-12-STABLE - FREEBSD-12-0 - FREEBSD-11-STABLE - FREEBSD-11-0 - FREEBSD-10-STABLE - FREEBSD-10-0 - FREEBSD-9-STABLE - FREEBSD-9-0 - FREEBSD-8-STABLE - FREEBSD-8-0 - FREEBSD-7-STABLE - FREEBSD-7-0 - FREEBSD-6-STABLE - FREEBSD-6-0 - FREEBSD-5-STABLE - FREEBSD-5-0 - FREEBSD-4-STABLE - FREEBSD-3-STABLE - FREEBSD22 - l41 - OPENBSD - linux-2.6 - MK84 - PLAN9 - xnu-8792
SearchContext: - none - 3 - 10

    1 /* $Id: dma.c,v 1.7 1994/12/28 03:35:33 root Exp root $
    2  * linux/kernel/dma.c: A DMA channel allocator. Inspired by linux/kernel/irq.c.
    3  *
    4  * Written by Hennus Bergman, 1992.
    5  *
    6  * 1994/12/26: Changes by Alex Nash to fix a minor bug in /proc/dma.
    7  *   In the previous version the reported device could end up being wrong,
    8  *   if a device requested a DMA channel that was already in use.
    9  *   [It also happened to remove the sizeof(char *) == sizeof(int)
   10  *   assumption introduced because of those /proc/dma patches. -- Hennus]
   11  */
   12 
   13 #include <linux/kernel.h>
   14 #include <linux/errno.h>
   15 #include <linux/spinlock.h>
   16 #include <linux/string.h>
   17 #include <asm/dma.h>
   18 #include <asm/system.h>
   19 
   20  
   21 
   22 /* A note on resource allocation:
   23  *
   24  * All drivers needing DMA channels, should allocate and release them
   25  * through the public routines `request_dma()' and `free_dma()'.
   26  *
   27  * In order to avoid problems, all processes should allocate resources in
   28  * the same sequence and release them in the reverse order.
   29  *
   30  * So, when allocating DMAs and IRQs, first allocate the IRQ, then the DMA.
   31  * When releasing them, first release the DMA, then release the IRQ.
   32  * If you don't, you may cause allocation requests to fail unnecessarily.
   33  * This doesn't really matter now, but it will once we get real semaphores
   34  * in the kernel.
   35  */
   36 
   37 
   38 spinlock_t dma_spin_lock = SPIN_LOCK_UNLOCKED;
   39 
   40 /*
   41  *      If our port doesn't define this it has no PC like DMA
   42  */
   43 
   44 #ifdef MAX_DMA_CHANNELS
   45 
   46 
   47 /* Channel n is busy iff dma_chan_busy[n].lock != 0.
   48  * DMA0 used to be reserved for DRAM refresh, but apparently not any more...
   49  * DMA4 is reserved for cascading.
   50  */
   51 
   52 struct dma_chan {
   53         int  lock;
   54         const char *device_id;
   55 };
   56 
   57 static struct dma_chan dma_chan_busy[MAX_DMA_CHANNELS] = {
   58         { 0, 0 },
   59         { 0, 0 },
   60         { 0, 0 },
   61         { 0, 0 },
   62         { 1, "cascade" },
   63         { 0, 0 },
   64         { 0, 0 },
   65         { 0, 0 }
   66 };
   67 
   68 int get_dma_list(char *buf)
   69 {
   70         int i, len = 0;
   71 
   72         for (i = 0 ; i < MAX_DMA_CHANNELS ; i++) {
   73                 if (dma_chan_busy[i].lock) {
   74                     len += sprintf(buf+len, "%2d: %s\n",
   75                                    i,
   76                                    dma_chan_busy[i].device_id);
   77                 }
   78         }
   79         return len;
   80 } /* get_dma_list */
   81 
   82 
   83 int request_dma(unsigned int dmanr, const char * device_id)
   84 {
   85         if (dmanr >= MAX_DMA_CHANNELS)
   86                 return -EINVAL;
   87 
   88         if (xchg(&dma_chan_busy[dmanr].lock, 1) != 0)
   89                 return -EBUSY;
   90 
   91         dma_chan_busy[dmanr].device_id = device_id;
   92 
   93         /* old flag was 0, now contains 1 to indicate busy */
   94         return 0;
   95 } /* request_dma */
   96 
   97 
   98 void free_dma(unsigned int dmanr)
   99 {
  100         if (dmanr >= MAX_DMA_CHANNELS) {
  101                 printk("Trying to free DMA%d\n", dmanr);
  102                 return;
  103         }
  104 
  105         if (xchg(&dma_chan_busy[dmanr].lock, 0) == 0) {
  106                 printk("Trying to free free DMA%d\n", dmanr);
  107                 return;
  108         }       
  109 
  110 } /* free_dma */
  111 
  112 #else
  113 
  114 int request_dma(unsigned int dmanr, const char *device_id)
  115 {
  116         return -EINVAL;
  117 }
  118 
  119 void free_dma(unsigned int dmanr)
  120 {
  121 }
  122 
  123 int get_dma_list(char *buf)
  124 {       
  125         strcpy(buf, "No DMA\n");
  126         return 7;
  127 }
  128 #endif

Cache object: caf45811ab2ebbbcd40c85d756a9096c

[ source navigation ] [ diff markup ] [ identifier search ] [ freetext search ] [ file search ] [ list types ] [ track identifier ]

This page is part of the FreeBSD/Linux Linux Kernel Cross-Reference, and was automatically generated using a modified version of the LXR engine.

FreeBSD/Linux Kernel Cross Reference sys/kernel/dma.c

FreeBSD/Linux Kernel Cross Reference
sys/kernel/dma.c