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

Showing the changes to include/linux/comedi (1 of 2 files). Show all

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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;