From owner-freebsd-hackers  Fri Aug 10 20:11:40 2001
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Date: Fri, 10 Aug 2001 23:05:28 -0400
From: Assem Salama <assem@twcny.rr.com>
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To: "freebsd-hackers@freebsd.org" <freebsd-hackers@freebsd.org>
Subject: dma_tag_create
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Hello,
    What is the meaning of the maxsegsz argument of dma_tag_create? It
doesn't seam to have any effect.

This is my code:

        /* try to allocate some DMA memory */
        if(bus_dma_tag_create(  NULL,                   /* parent */
                                (1<<16),                /* allignment
(64K) */
                                (0),                    /* boundry */
                                BUS_SPACE_MAXSIZE_32BIT,/* lowaddr */
                                BUS_SPACE_MAXSIZE,      /* high addr */
                                NULL, NULL,             /* filter,
filterarg */
                                (1<<14),                /* maxsize
(256K) */
                                4,                      /* num segs */
                                (1<<10),                /* maxsegsize */

                                0,
                                &dma_tag))
        {
                PRINTERR("Could not make the DMA tag!\n");
                return ENXIO;
        }
        if(bus_dmamem_alloc(dma_tag, (void*)&DMA_buffer, BUS_DMA_NOWAIT,
&dma_map)) {
                PRINTERR("Could not allocate memory!\n");
                bus_dma_tag_destroy(dma_tag);
                return ENXIO;
        }
        if(bus_dmamap_load(dma_tag, dma_map, DMA_buffer, (1<<12),
ide_mod_load_map, &phys_addr, 0)) {
                PRINTERR("Could not load the map!\n");
                bus_dmamem_free(dma_tag, DMA_buffer, dma_map);
                bus_dma_tag_destroy(dma_tag);
                return ENXIO;
        }

Thanks,
Assem Salama

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