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

  *
  * A COMEDI data buffer is allocated as individual pages, either in
  * conventional memory or DMA coherent memory, depending on the attached,
- * low-level hardware device.  (The buffer pages also get mapped into the
+ * low-level hardware device.
- * kernel's contiguous virtual address space pointed to by the 'prealloc_buf'
- * member of &struct comedi_async.)
  *
  * The buffer is normally freed when the COMEDI device is detached from the
  * low-level driver (which may happen due to device removal), but if it happens
  * to be mmapped at the time, the pages cannot be freed until the buffer has
- * been munmapped.  That is what the reference counter is for.  (The virtual
+ * been munmapped.  That is what the reference counter is for.
- * address space pointed by 'prealloc_buf' is freed when the COMEDI device is
- * detached.)
  */
 struct comedi_buf_map {
 	struct device *dma_hw_dev;
 /**
  * struct comedi_async - Control data for asynchronous COMEDI commands
- * @prealloc_buf: Kernel virtual address of allocated acquisition buffer.
  * @prealloc_bufsz: Buffer size (in bytes).
  * @buf_map: Map of buffer pages.
  * @max_bufsize: Maximum allowed buffer size (in bytes).
  * less than or equal to UINT_MAX).
  */
 struct comedi_async {
-	void *prealloc_buf;
 	unsigned int prealloc_bufsz;
 	struct comedi_buf_map *buf_map;
 	unsigned int max_bufsize;