From 11a10830b6e1ed001e0d71594beb5eedc714e202 Mon Sep 17 00:00:00 2001 From: Ian Abbott Date: Mon, 21 Sep 2015 18:52:52 +0100 Subject: [PATCH] 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 Reviewed-by: H Hartley Sweeten Signed-off-by: Greg Kroah-Hartman --- drivers/staging/comedi/comedidev.h | 29 +++++++++++++++++++++++++++++ 1 file changed, 29 insertions(+) diff --git a/drivers/staging/comedi/comedidev.h b/drivers/staging/comedi/comedidev.h index ccd761b..cfb7d52 100644 --- a/drivers/staging/comedi/comedidev.h +++ b/drivers/staging/comedi/comedidev.h @@ -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; -- 2.7.4