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staging: comedi: comedidev.h: document struct comedi_buf_map 

Add kernel-doc for `struct comedi_buf_map` and the associated `struct
comedi_buf_page`.

Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Reviewed-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Ian Abbott 2015-09-21 18:52:52 +01:00 committed by Greg Kroah-Hartman
parent 0f952fa843
commit 11a10830b6
1 changed files with 29 additions and 0 deletions
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29
drivers/staging/comedi/comedidev.h
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@ -217,11 +217,40 @@ struct comedi_subdevice {
unsigned int *readback;
};
/**
* struct comedi_buf_page - Describe a page of a COMEDI buffer
* @virt_addr: Kernel address of page.
* @dma_addr: DMA address of page if in DMA coherent memory.
*/
struct comedi_buf_page {
void *virt_addr;
dma_addr_t dma_addr;
};
/**
* struct comedi_buf_map - Describe pages in a COMEDI buffer
* @dma_hw_dev: Low-level hardware &struct device pointer copied from the
* COMEDI device's hw_dev member.
* @page_list: Pointer to array of &struct comedi_buf_page, one for each
* page in the buffer.
* @n_pages: Number of pages in the buffer.
* @dma_dir: DMA direction used to allocate pages of DMA coherent memory,
* or %DMA_NONE if pages allocated from regular memory.
* @refcount: &struct kref reference counter used to free the buffer.
*
* 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
* 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
* 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_buf_page *page_list;