comedi: remove the mapping of the Comedi buffer in vmalloc address space

Now that all the code that accesses the Comedi buffer data does so page-by-page, using the `virt_addr` member of `struct comedi_buf_page` to point to the data of each page, do not linearly map the buffer into vmalloc address space (pointed to by the `prealloc_buf` member of `struct comedi_async`). That was only done for convenience, but was not done for those drivers that need a DMA coherent buffer, which is allocated in a single chunk. Remove the `prealloc_buf` member as it is no longer used.

Ian Abbott committed 1 year ago

Commit 5117f281 parent e7199b62 files · +6 −49Browse files

Unified · Split

2 files

drivers/comedi/comedi_buf.c +4 −41
include/linux/comedi/comedidev.h +2 −8

drivers/comedi/comedi_buf.c+4−41

@@ -56,13 +56,7 @@ static void __comedi_buf_free(struct comedi_device *dev, · 55 unmodified lines
56	56	struct comedi_buf_map *bm;
57	57	unsigned long flags;
58	58
59		− if (async->prealloc_buf) {
60		− if (s->async_dma_dir == DMA_NONE)
61		− vunmap(async->prealloc_buf);
62		− async->prealloc_buf = NULL;
63		− async->prealloc_bufsz = 0;
64		− }
65		−
	59	+ async->prealloc_bufsz = 0;
66	60	spin_lock_irqsave(&s->spin_lock, flags);
67	61	bm = async->buf_map;
68	62	async->buf_map = NULL;
@@ -141,11 +135,8 @@ static void __comedi_buf_alloc(struct comedi_device *dev, · 72 unmodified lines
141	135	unsigned int n_pages)
142	136	{
143	137	struct comedi_async *async = s->async;
144		− struct page **pages = NULL;
145	138	struct comedi_buf_map *bm;
146		− struct comedi_buf_page *buf;
147	139	unsigned long flags;
148		− unsigned int i;
149	140
150	141	if (!IS_ENABLED(CONFIG_HAS_DMA) && s->async_dma_dir != DMA_NONE) {
151	142	dev_err(dev->class_dev,
@@ -160,30 +151,7 @@ static void __comedi_buf_alloc(struct comedi_device *dev, · 8 unmodified lines
160	151	spin_lock_irqsave(&s->spin_lock, flags);
161	152	async->buf_map = bm;
162	153	spin_unlock_irqrestore(&s->spin_lock, flags);
163		−
164		− if (bm->dma_dir != DMA_NONE) {
165		− /*
166		− * DMA buffer was allocated as a single block.
167		− * Address is in page_list[0].
168		− */
169		− buf = &bm->page_list[0];
170		− async->prealloc_buf = buf->virt_addr;
171		− } else {
172		− pages = vmalloc(sizeof(struct page ) n_pages);
173		− if (!pages)
174		− return;
175		−
176		− for (i = 0; i < n_pages; i++) {
177		− buf = &bm->page_list[i];
178		− pages[i] = virt_to_page(buf->virt_addr);
179		− }
180		−
181		− /* vmap the pages to prealloc_buf */
182		− async->prealloc_buf = vmap(pages, n_pages, VM_MAP,
183		− COMEDI_PAGE_PROTECTION);
184		−
185		− vfree(pages);
186		− }
	154	+ async->prealloc_bufsz = n_pages << PAGE_SHIFT;
187	155	}
188	156
189	157	void comedi_buf_map_get(struct comedi_buf_map *bm)
@@ -264,7 +232,7 @@ int comedi_buf_alloc(struct comedi_device dev, struct comedi_subdevice s, · 74 unmodified lines
264	232	new_size = (new_size + PAGE_SIZE - 1) & PAGE_MASK;
265	233
266	234	/* if no change is required, do nothing */
267		− if (async->prealloc_buf && async->prealloc_bufsz == new_size)
	235	+ if (async->prealloc_bufsz == new_size)
268	236	return 0;
269	237
270	238	/* deallocate old buffer */
@@ -275,14 +243,9 @@ int comedi_buf_alloc(struct comedi_device dev, struct comedi_subdevice s, · 4 unmodified lines
275	243	unsigned int n_pages = new_size >> PAGE_SHIFT;
276	244
277	245	__comedi_buf_alloc(dev, s, n_pages);
278		−
279		− if (!async->prealloc_buf) {
280		− /* allocation failed */
281		− __comedi_buf_free(dev, s);
	246	+ if (!async->prealloc_bufsz)
282	247	return -ENOMEM;
283		− }
284	248	}
285		− async->prealloc_bufsz = new_size;
286	249
287	250	return 0;
288	251	}

include/linux/comedi/comedidev.h+2−8

@@ -234,16 +234,12 @@ struct comedi_buf_page { · 233 unmodified lines
234	234	*
235	235	* A COMEDI data buffer is allocated as individual pages, either in
236	236	* conventional memory or DMA coherent memory, depending on the attached,
237		− * low-level hardware device. (The buffer pages also get mapped into the
238		− * kernel's contiguous virtual address space pointed to by the 'prealloc_buf'
239		− * member of &struct comedi_async.)
	237	+ * low-level hardware device.
240	238	*
241	239	* The buffer is normally freed when the COMEDI device is detached from the
242	240	* low-level driver (which may happen due to device removal), but if it happens
243	241	* to be mmapped at the time, the pages cannot be freed until the buffer has
244		− * been munmapped. That is what the reference counter is for. (The virtual
245		− * address space pointed by 'prealloc_buf' is freed when the COMEDI device is
246		− * detached.)
	242	+ * been munmapped. That is what the reference counter is for.
247	243	*/
248	244	struct comedi_buf_map {
249	245	struct device *dma_hw_dev;
@@ -255,7 +251,6 @@ struct comedi_buf_map { · 5 unmodified lines
255	251
256	252	/**
257	253	* struct comedi_async - Control data for asynchronous COMEDI commands
258		− * @prealloc_buf: Kernel virtual address of allocated acquisition buffer.
259	254	* @prealloc_bufsz: Buffer size (in bytes).
260	255	* @buf_map: Map of buffer pages.
261	256	* @max_bufsize: Maximum allowed buffer size (in bytes).
@@ -344,7 +339,6 @@ struct comedi_buf_map { · 82 unmodified lines
344	339	* less than or equal to UINT_MAX).
345	340	*/
346	341	struct comedi_async {
347		− void *prealloc_buf;
348	342	unsigned int prealloc_bufsz;
349	343	struct comedi_buf_map *buf_map;
350	344	unsigned int max_bufsize;