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

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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.

Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Link: https://lore.kernel.org/r/20250415114008.5977-4-abbotti@mev.co.uk
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Ian Abbott
2025-04-15 12:35:58 +01:00
committed by Greg Kroah-Hartman
parent e7199b6b59
commit 5117f28a7d
2 changed files with 6 additions and 49 deletions
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10
include/linux/comedi/comedidev.h
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@@ -234,16 +234,12 @@ struct comedi_buf_page {
*
* 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.)
* low-level hardware device.
*
* 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.)
* been munmapped. That is what the reference counter is for.
*/
struct comedi_buf_map {
struct device *dma_hw_dev;
@@ -255,7 +251,6 @@ struct comedi_buf_map {
/**
* 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).
@@ -344,7 +339,6 @@ struct comedi_buf_map {
* 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;