Current Path : /sys/dev/drm/ |
FreeBSD hs32.drive.ne.jp 9.1-RELEASE FreeBSD 9.1-RELEASE #1: Wed Jan 14 12:18:08 JST 2015 root@hs32.drive.ne.jp:/sys/amd64/compile/hs32 amd64 |
Current File : //sys/dev/drm/via_dmablit.c |
/* via_dmablit.c -- PCI DMA BitBlt support for the VIA Unichrome/Pro * * Copyright (C) 2005 Thomas Hellstrom, All Rights Reserved. * * Permission is hereby granted, free of charge, to any person obtaining a * copy of this software and associated documentation files (the "Software"), * to deal in the Software without restriction, including without limitation * the rights to use, copy, modify, merge, publish, distribute, sub license, * and/or sell copies of the Software, and to permit persons to whom the * Software is furnished to do so, subject to the following conditions: * * The above copyright notice and this permission notice (including the * next paragraph) shall be included in all copies or substantial portions * of the Software. * * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, * FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL * THE COPYRIGHT HOLDERS, AUTHORS AND/OR ITS SUPPLIERS BE LIABLE FOR ANY CLAIM, * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR * OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE * USE OR OTHER DEALINGS IN THE SOFTWARE. * * Authors: * Thomas Hellstrom. * Partially based on code obtained from Digeo Inc. */ #include <sys/cdefs.h> __FBSDID("$FreeBSD: release/9.1.0/sys/dev/drm/via_dmablit.c 216699 2010-12-25 21:26:56Z alc $"); /* * Unmaps the DMA mappings. * FIXME: Is this a NoOp on x86? Also * FIXME: What happens if this one is called and a pending blit has previously done * the same DMA mappings? */ #include "dev/drm/drmP.h" #include "dev/drm/via_drm.h" #include "dev/drm/via_drv.h" #include "dev/drm/via_dmablit.h" #define VIA_PGDN(x) (((unsigned long)(x)) & ~PAGE_MASK) #define VIA_PGOFF(x) (((unsigned long)(x)) & PAGE_MASK) #define VIA_PFN(x) ((unsigned long)(x) >> PAGE_SHIFT) typedef struct _drm_via_descriptor { uint32_t mem_addr; uint32_t dev_addr; uint32_t size; uint32_t next; } drm_via_descriptor_t; static void via_dmablit_timer(void *arg); /* * Unmap a DMA mapping. */ static void via_unmap_blit_from_device(drm_via_sg_info_t *vsg) { int num_desc = vsg->num_desc; unsigned cur_descriptor_page = num_desc / vsg->descriptors_per_page; unsigned descriptor_this_page = num_desc % vsg->descriptors_per_page; drm_via_descriptor_t *desc_ptr = vsg->desc_pages[cur_descriptor_page] + descriptor_this_page; dma_addr_t next = vsg->chain_start; while(num_desc--) { if (descriptor_this_page-- == 0) { cur_descriptor_page--; descriptor_this_page = vsg->descriptors_per_page - 1; desc_ptr = vsg->desc_pages[cur_descriptor_page] + descriptor_this_page; } next = (dma_addr_t) desc_ptr->next; desc_ptr--; } } /* * If mode = 0, count how many descriptors are needed. * If mode = 1, Map the DMA pages for the device, put together and map also the descriptors. * Descriptors are run in reverse order by the hardware because we are not allowed to update the * 'next' field without syncing calls when the descriptor is already mapped. */ static void via_map_blit_for_device(const drm_via_dmablit_t *xfer, drm_via_sg_info_t *vsg, int mode) { unsigned cur_descriptor_page = 0; unsigned num_descriptors_this_page = 0; unsigned char *mem_addr = xfer->mem_addr; unsigned char *cur_mem; unsigned char *first_addr = (unsigned char *)VIA_PGDN(mem_addr); uint32_t fb_addr = xfer->fb_addr; uint32_t cur_fb; unsigned long line_len; unsigned remaining_len; int num_desc = 0; int cur_line; dma_addr_t next = 0 | VIA_DMA_DPR_EC; drm_via_descriptor_t *desc_ptr = NULL; if (mode == 1) desc_ptr = vsg->desc_pages[cur_descriptor_page]; for (cur_line = 0; cur_line < xfer->num_lines; ++cur_line) { line_len = xfer->line_length; cur_fb = fb_addr; cur_mem = mem_addr; while (line_len > 0) { remaining_len = min(PAGE_SIZE - VIA_PGOFF(cur_mem), line_len); line_len -= remaining_len; if (mode == 1) { desc_ptr->mem_addr = VM_PAGE_TO_PHYS( vsg->pages[VIA_PFN(cur_mem) - VIA_PFN(first_addr)]) + VIA_PGOFF(cur_mem); desc_ptr->dev_addr = cur_fb; desc_ptr->size = remaining_len; desc_ptr->next = (uint32_t) next; next = vtophys(desc_ptr); desc_ptr++; if (++num_descriptors_this_page >= vsg->descriptors_per_page) { num_descriptors_this_page = 0; desc_ptr = vsg->desc_pages[++cur_descriptor_page]; } } num_desc++; cur_mem += remaining_len; cur_fb += remaining_len; } mem_addr += xfer->mem_stride; fb_addr += xfer->fb_stride; } if (mode == 1) { vsg->chain_start = next; vsg->state = dr_via_device_mapped; } vsg->num_desc = num_desc; } /* * Function that frees up all resources for a blit. It is usable even if the * blit info has only been partially built as long as the status enum is consistent * with the actual status of the used resources. */ static void via_free_sg_info(drm_via_sg_info_t *vsg) { vm_page_t page; int i; switch(vsg->state) { case dr_via_device_mapped: via_unmap_blit_from_device(vsg); case dr_via_desc_pages_alloc: for (i=0; i<vsg->num_desc_pages; ++i) { if (vsg->desc_pages[i] != NULL) free(vsg->desc_pages[i], DRM_MEM_PAGES); } free(vsg->desc_pages, DRM_MEM_DRIVER); case dr_via_pages_locked: for (i=0; i < vsg->num_pages; ++i) { page = vsg->pages[i]; vm_page_lock(page); vm_page_unwire(page, 0); vm_page_unlock(page); } case dr_via_pages_alloc: free(vsg->pages, DRM_MEM_DRIVER); default: vsg->state = dr_via_sg_init; } free(vsg->bounce_buffer, DRM_MEM_DRIVER); vsg->bounce_buffer = NULL; vsg->free_on_sequence = 0; } /* * Fire a blit engine. */ static void via_fire_dmablit(struct drm_device *dev, drm_via_sg_info_t *vsg, int engine) { drm_via_private_t *dev_priv = (drm_via_private_t *)dev->dev_private; VIA_WRITE(VIA_PCI_DMA_MAR0 + engine*0x10, 0); VIA_WRITE(VIA_PCI_DMA_DAR0 + engine*0x10, 0); VIA_WRITE(VIA_PCI_DMA_CSR0 + engine*0x04, VIA_DMA_CSR_DD | VIA_DMA_CSR_TD | VIA_DMA_CSR_DE); VIA_WRITE(VIA_PCI_DMA_MR0 + engine*0x04, VIA_DMA_MR_CM | VIA_DMA_MR_TDIE); VIA_WRITE(VIA_PCI_DMA_BCR0 + engine*0x10, 0); VIA_WRITE(VIA_PCI_DMA_DPR0 + engine*0x10, vsg->chain_start); DRM_WRITEMEMORYBARRIER(); VIA_WRITE(VIA_PCI_DMA_CSR0 + engine*0x04, VIA_DMA_CSR_DE | VIA_DMA_CSR_TS); VIA_READ(VIA_PCI_DMA_CSR0 + engine*0x04); } /* * Obtain a page pointer array and lock all pages into system memory. A segmentation violation will * occur here if the calling user does not have access to the submitted address. */ static int via_lock_all_dma_pages(drm_via_sg_info_t *vsg, drm_via_dmablit_t *xfer) { unsigned long first_pfn = VIA_PFN(xfer->mem_addr); vm_page_t m; int i; vsg->num_pages = VIA_PFN(xfer->mem_addr + (xfer->num_lines * xfer->mem_stride -1)) - first_pfn + 1; if (NULL == (vsg->pages = malloc(sizeof(vm_page_t) * vsg->num_pages, DRM_MEM_DRIVER, M_NOWAIT))) return -ENOMEM; vsg->state = dr_via_pages_alloc; if (vm_fault_quick_hold_pages(&curproc->p_vmspace->vm_map, (vm_offset_t)xfer->mem_addr, vsg->num_pages * PAGE_SIZE, VM_PROT_READ | VM_PROT_WRITE, vsg->pages, vsg->num_pages) < 0) return -EACCES; for (i = 0; i < vsg->num_pages; i++) { m = vsg->pages[i]; vm_page_lock(m); vm_page_wire(m); vm_page_unhold(m); vm_page_unlock(m); } vsg->state = dr_via_pages_locked; DRM_DEBUG("DMA pages locked\n"); return 0; } /* * Allocate DMA capable memory for the blit descriptor chain, and an array that keeps track of the * pages we allocate. We don't want to use kmalloc for the descriptor chain because it may be * quite large for some blits, and pages don't need to be contingous. */ static int via_alloc_desc_pages(drm_via_sg_info_t *vsg) { int i; vsg->descriptors_per_page = PAGE_SIZE / sizeof(drm_via_descriptor_t); vsg->num_desc_pages = (vsg->num_desc + vsg->descriptors_per_page - 1) / vsg->descriptors_per_page; if (NULL == (vsg->desc_pages = malloc(vsg->num_desc_pages * sizeof(void *), DRM_MEM_DRIVER, M_NOWAIT | M_ZERO))) return -ENOMEM; vsg->state = dr_via_desc_pages_alloc; for (i = 0; i < vsg->num_desc_pages; ++i) { if (NULL == (vsg->desc_pages[i] = (drm_via_descriptor_t *)malloc(PAGE_SIZE, DRM_MEM_PAGES, M_NOWAIT | M_ZERO))) return -ENOMEM; } DRM_DEBUG("Allocated %d pages for %d descriptors.\n", vsg->num_desc_pages, vsg->num_desc); return 0; } static void via_abort_dmablit(struct drm_device *dev, int engine) { drm_via_private_t *dev_priv = (drm_via_private_t *)dev->dev_private; VIA_WRITE(VIA_PCI_DMA_CSR0 + engine*0x04, VIA_DMA_CSR_TA); } static void via_dmablit_engine_off(struct drm_device *dev, int engine) { drm_via_private_t *dev_priv = (drm_via_private_t *)dev->dev_private; VIA_WRITE(VIA_PCI_DMA_CSR0 + engine*0x04, VIA_DMA_CSR_TD | VIA_DMA_CSR_DD); } /* * The dmablit part of the IRQ handler. Trying to do only reasonably fast things here. * The rest, like unmapping and freeing memory for done blits is done in a separate workqueue * task. Basically the task of the interrupt handler is to submit a new blit to the engine, while * the workqueue task takes care of processing associated with the old blit. */ void via_dmablit_handler(struct drm_device *dev, int engine, int from_irq) { drm_via_private_t *dev_priv = (drm_via_private_t *)dev->dev_private; drm_via_blitq_t *blitq = dev_priv->blit_queues + engine; int cur; int done_transfer; uint32_t status = 0; DRM_DEBUG("DMA blit handler called. engine = %d, from_irq = %d, blitq = 0x%lx\n", engine, from_irq, (unsigned long) blitq); mtx_lock(&blitq->blit_lock); done_transfer = blitq->is_active && (( status = VIA_READ(VIA_PCI_DMA_CSR0 + engine*0x04)) & VIA_DMA_CSR_TD); done_transfer = done_transfer || ( blitq->aborting && !(status & VIA_DMA_CSR_DE)); cur = blitq->cur; if (done_transfer) { blitq->blits[cur]->aborted = blitq->aborting; blitq->done_blit_handle++; DRM_WAKEUP(&blitq->blit_queue[cur]); cur++; if (cur >= VIA_NUM_BLIT_SLOTS) cur = 0; blitq->cur = cur; /* * Clear transfer done flag. */ VIA_WRITE(VIA_PCI_DMA_CSR0 + engine*0x04, VIA_DMA_CSR_TD); blitq->is_active = 0; blitq->aborting = 0; taskqueue_enqueue(taskqueue_swi, &blitq->wq); } else if (blitq->is_active && (ticks >= blitq->end)) { /* * Abort transfer after one second. */ via_abort_dmablit(dev, engine); blitq->aborting = 1; blitq->end = ticks + DRM_HZ; } if (!blitq->is_active) { if (blitq->num_outstanding) { via_fire_dmablit(dev, blitq->blits[cur], engine); blitq->is_active = 1; blitq->cur = cur; blitq->num_outstanding--; blitq->end = ticks + DRM_HZ; if (!callout_pending(&blitq->poll_timer)) callout_reset(&blitq->poll_timer, 1, (timeout_t *)via_dmablit_timer, (void *)blitq); } else { if (callout_pending(&blitq->poll_timer)) { callout_stop(&blitq->poll_timer); } via_dmablit_engine_off(dev, engine); } } mtx_unlock(&blitq->blit_lock); } /* * Check whether this blit is still active, performing necessary locking. */ static int via_dmablit_active(drm_via_blitq_t *blitq, int engine, uint32_t handle, wait_queue_head_t **queue) { uint32_t slot; int active; mtx_lock(&blitq->blit_lock); /* * Allow for handle wraparounds. */ active = ((blitq->done_blit_handle - handle) > (1 << 23)) && ((blitq->cur_blit_handle - handle) <= (1 << 23)); if (queue && active) { slot = handle - blitq->done_blit_handle + blitq->cur -1; if (slot >= VIA_NUM_BLIT_SLOTS) { slot -= VIA_NUM_BLIT_SLOTS; } *queue = blitq->blit_queue + slot; } mtx_unlock(&blitq->blit_lock); return active; } /* * Sync. Wait for at least three seconds for the blit to be performed. */ static int via_dmablit_sync(struct drm_device *dev, uint32_t handle, int engine) { drm_via_private_t *dev_priv = (drm_via_private_t *)dev->dev_private; drm_via_blitq_t *blitq = dev_priv->blit_queues + engine; wait_queue_head_t *queue; int ret = 0; if (via_dmablit_active(blitq, engine, handle, &queue)) { DRM_WAIT_ON(ret, *queue, 3 * DRM_HZ, !via_dmablit_active(blitq, engine, handle, NULL)); } DRM_DEBUG("DMA blit sync handle 0x%x engine %d returned %d\n", handle, engine, ret); return ret; } /* * A timer that regularly polls the blit engine in cases where we don't have interrupts: * a) Broken hardware (typically those that don't have any video capture facility). * b) Blit abort. The hardware doesn't send an interrupt when a blit is aborted. * The timer and hardware IRQ's can and do work in parallel. If the hardware has * irqs, it will shorten the latency somewhat. */ static void via_dmablit_timer(void *arg) { drm_via_blitq_t *blitq = (drm_via_blitq_t *)arg; struct drm_device *dev = blitq->dev; int engine = (int) (blitq - ((drm_via_private_t *)dev->dev_private)->blit_queues); DRM_DEBUG("Polling timer called for engine %d, jiffies %lu\n", engine, (unsigned long) jiffies); via_dmablit_handler(dev, engine, 0); if (!callout_pending(&blitq->poll_timer)) { callout_schedule(&blitq->poll_timer, 1); /* * Rerun handler to delete timer if engines are off, and * to shorten abort latency. This is a little nasty. */ via_dmablit_handler(dev, engine, 0); } } /* * Workqueue task that frees data and mappings associated with a blit. * Also wakes up waiting processes. Each of these tasks handles one * blit engine only and may not be called on each interrupt. */ static void via_dmablit_workqueue(void *arg, int pending) { drm_via_blitq_t *blitq = (drm_via_blitq_t *)arg; struct drm_device *dev = blitq->dev; drm_via_sg_info_t *cur_sg; int cur_released; DRM_DEBUG("task called for blit engine %ld\n",(unsigned long) (blitq - ((drm_via_private_t *)dev->dev_private)->blit_queues)); mtx_lock(&blitq->blit_lock); while(blitq->serviced != blitq->cur) { cur_released = blitq->serviced++; DRM_DEBUG("Releasing blit slot %d\n", cur_released); if (blitq->serviced >= VIA_NUM_BLIT_SLOTS) blitq->serviced = 0; cur_sg = blitq->blits[cur_released]; blitq->num_free++; mtx_unlock(&blitq->blit_lock); DRM_WAKEUP(&blitq->busy_queue); via_free_sg_info(cur_sg); free(cur_sg, DRM_MEM_DRIVER); mtx_lock(&blitq->blit_lock); } mtx_unlock(&blitq->blit_lock); } /* * Init all blit engines. Currently we use two, but some hardware have 4. */ void via_init_dmablit(struct drm_device *dev) { int i,j; drm_via_private_t *dev_priv = (drm_via_private_t *)dev->dev_private; drm_via_blitq_t *blitq; for (i=0; i< VIA_NUM_BLIT_ENGINES; ++i) { blitq = dev_priv->blit_queues + i; blitq->dev = dev; blitq->cur_blit_handle = 0; blitq->done_blit_handle = 0; blitq->head = 0; blitq->cur = 0; blitq->serviced = 0; blitq->num_free = VIA_NUM_BLIT_SLOTS - 1; blitq->num_outstanding = 0; blitq->is_active = 0; blitq->aborting = 0; mtx_init(&blitq->blit_lock, "via_blit_lk", NULL, MTX_DEF); for (j=0; j<VIA_NUM_BLIT_SLOTS; ++j) { DRM_INIT_WAITQUEUE(blitq->blit_queue + j); } DRM_INIT_WAITQUEUE(&blitq->busy_queue); TASK_INIT(&blitq->wq, 0, via_dmablit_workqueue, blitq); callout_init(&blitq->poll_timer, 0); } } /* * Build all info and do all mappings required for a blit. */ static int via_build_sg_info(struct drm_device *dev, drm_via_sg_info_t *vsg, drm_via_dmablit_t *xfer) { int ret = 0; vsg->bounce_buffer = NULL; vsg->state = dr_via_sg_init; if (xfer->num_lines <= 0 || xfer->line_length <= 0) { DRM_ERROR("Zero size bitblt.\n"); return -EINVAL; } /* * Below check is a driver limitation, not a hardware one. We * don't want to lock unused pages, and don't want to incoporate the * extra logic of avoiding them. Make sure there are no. * (Not a big limitation anyway.) */ if ((xfer->mem_stride - xfer->line_length) > 2 * PAGE_SIZE) { DRM_ERROR("Too large system memory stride. Stride: %d, " "Length: %d\n", xfer->mem_stride, xfer->line_length); return -EINVAL; } if ((xfer->mem_stride == xfer->line_length) && (xfer->fb_stride == xfer->line_length)) { xfer->mem_stride *= xfer->num_lines; xfer->line_length = xfer->mem_stride; xfer->fb_stride = xfer->mem_stride; xfer->num_lines = 1; } /* * Don't lock an arbitrary large number of pages, since that causes a * DOS security hole. */ if (xfer->num_lines > 2048 || (xfer->num_lines*xfer->mem_stride > (2048*2048*4))) { DRM_ERROR("Too large PCI DMA bitblt.\n"); return -EINVAL; } /* * we allow a negative fb stride to allow flipping of images in * transfer. */ if (xfer->mem_stride < xfer->line_length || abs(xfer->fb_stride) < xfer->line_length) { DRM_ERROR("Invalid frame-buffer / memory stride.\n"); return -EINVAL; } /* * A hardware bug seems to be worked around if system memory addresses * start on 16 byte boundaries. This seems a bit restrictive however. * VIA is contacted about this. Meanwhile, impose the following * restrictions: */ #ifdef VIA_BUGFREE if ((((unsigned long)xfer->mem_addr & 3) != ((unsigned long)xfer->fb_addr & 3)) || ((xfer->num_lines > 1) && ((xfer->mem_stride & 3) != (xfer->fb_stride & 3)))) { DRM_ERROR("Invalid DRM bitblt alignment.\n"); return -EINVAL; } #else if ((((unsigned long)xfer->mem_addr & 15) || ((unsigned long)xfer->fb_addr & 3)) || ((xfer->num_lines > 1) && ((xfer->mem_stride & 15) || (xfer->fb_stride & 3)))) { DRM_ERROR("Invalid DRM bitblt alignment.\n"); return -EINVAL; } #endif if (0 != (ret = via_lock_all_dma_pages(vsg, xfer))) { DRM_ERROR("Could not lock DMA pages.\n"); via_free_sg_info(vsg); return ret; } via_map_blit_for_device(xfer, vsg, 0); if (0 != (ret = via_alloc_desc_pages(vsg))) { DRM_ERROR("Could not allocate DMA descriptor pages.\n"); via_free_sg_info(vsg); return ret; } via_map_blit_for_device(xfer, vsg, 1); return 0; } /* * Reserve one free slot in the blit queue. Will wait for one second for one * to become available. Otherwise -EBUSY is returned. */ static int via_dmablit_grab_slot(drm_via_blitq_t *blitq, int engine) { struct drm_device *dev = blitq->dev; int ret=0; DRM_DEBUG("Num free is %d\n", blitq->num_free); mtx_lock(&blitq->blit_lock); while(blitq->num_free == 0) { mtx_unlock(&blitq->blit_lock); DRM_WAIT_ON(ret, blitq->busy_queue, DRM_HZ, blitq->num_free > 0); if (ret) { return (-EINTR == ret) ? -EAGAIN : ret; } mtx_lock(&blitq->blit_lock); } blitq->num_free--; mtx_unlock(&blitq->blit_lock); return 0; } /* * Hand back a free slot if we changed our mind. */ static void via_dmablit_release_slot(drm_via_blitq_t *blitq) { mtx_lock(&blitq->blit_lock); blitq->num_free++; mtx_unlock(&blitq->blit_lock); DRM_WAKEUP( &blitq->busy_queue ); } /* * Grab a free slot. Build blit info and queue a blit. */ static int via_dmablit(struct drm_device *dev, drm_via_dmablit_t *xfer) { drm_via_private_t *dev_priv = (drm_via_private_t *)dev->dev_private; drm_via_sg_info_t *vsg; drm_via_blitq_t *blitq; int ret; int engine; if (dev_priv == NULL) { DRM_ERROR("Called without initialization.\n"); return -EINVAL; } engine = (xfer->to_fb) ? 0 : 1; blitq = dev_priv->blit_queues + engine; if (0 != (ret = via_dmablit_grab_slot(blitq, engine))) { return ret; } if (NULL == (vsg = malloc(sizeof(*vsg), DRM_MEM_DRIVER, M_NOWAIT | M_ZERO))) { via_dmablit_release_slot(blitq); return -ENOMEM; } if (0 != (ret = via_build_sg_info(dev, vsg, xfer))) { via_dmablit_release_slot(blitq); free(vsg, DRM_MEM_DRIVER); return ret; } mtx_lock(&blitq->blit_lock); blitq->blits[blitq->head++] = vsg; if (blitq->head >= VIA_NUM_BLIT_SLOTS) blitq->head = 0; blitq->num_outstanding++; xfer->sync.sync_handle = ++blitq->cur_blit_handle; mtx_unlock(&blitq->blit_lock); xfer->sync.engine = engine; via_dmablit_handler(dev, engine, 0); return 0; } /* * Sync on a previously submitted blit. Note that the X server use signals * extensively, and that there is a very big probability that this IOCTL will * be interrupted by a signal. In that case it returns with -EAGAIN for the * signal to be delivered. The caller should then reissue the IOCTL. This is * similar to what is being done for drmGetLock(). */ int via_dma_blit_sync( struct drm_device *dev, void *data, struct drm_file *file_priv ) { drm_via_blitsync_t *sync = data; int err; if (sync->engine >= VIA_NUM_BLIT_ENGINES) return -EINVAL; err = via_dmablit_sync(dev, sync->sync_handle, sync->engine); if (-EINTR == err) err = -EAGAIN; return err; } /* * Queue a blit and hand back a handle to be used for sync. This IOCTL may be * interrupted by a signal while waiting for a free slot in the blit queue. * In that case it returns with -EAGAIN and should be reissued. See the above * IOCTL code. */ int via_dma_blit( struct drm_device *dev, void *data, struct drm_file *file_priv ) { drm_via_dmablit_t *xfer = data; int err; err = via_dmablit(dev, xfer); return err; }