[PATCH 0/3] dma_mapping: Add auto cleanup support

[Frank Li]

There are many below pattern

	fun()
	{
		...
		dma_map_single();
		if (dma_mapping_error)
			goto err1;

		dmaengine_prep_slave_single()
		if (...)
			goto err2

		dmaengine_submit()
		if (...)
			goto err3

		wait_for_completion_timeout()
		if (...)
			goto err4

	err4:
	err3:
	err2:
		dma_umap_single();
	err1:
	}

Use cleanup can simple error handle like guard(), such as guard(mutex).
or __free(kfree) = kmalloc.

But dma_umap_single() need more argurements. So situation below complex.

It need pack argurments list into structure.

	#define __DEFINE_GUARD_CLASS(_name, _return_type, _list_class_fields)   \
	typedef struct {                                                \
	       	 _return_type ret;                                       \
	        bool    okay;                                           \
	        struct  {                                               \
	                __REMOVE(_list_class_fields);                   \
	        } args;                                                 \
	} class_##_name##_t;

So save all arugments to it.

__DEFINE_GUARD_CLASS(dma_map_single, dma_addr_t, (struct device *dev; void *ptr; size_t size; enum dma_data_direction dir)
will expand to

	struct {
		dma_addr_t ret;
		bool	okay;
		struct {
			struct device *dev;
			void *ptr;
			size_t size;
			enum dma_data_direction dir;
		}
	}

So cleanup function can use saved argurement.

The above fun will be

	fun()
	{
		CLASS(dma_map_single, dma)(dev, ...);

		...
		if (...)
			return err;
	}

if funtion return, which need keep map,

	submit()
	{
		dma_map_single();
		...
		dmaengine_submit();
		if (...)
			goto err1
		return;

	goto err1:
		dma_umap_single();
	}

Macro retain_and_empty() will clean varible to avoid unmap.

        ({                                  \
                __auto_type __ptr = &(t); typeof(t) empty= {};   \
                __auto_type __val = *__ptr; \
                __ptr->okay = 0;        \
                __val.ret;              \
        })

So

	submit()
	{
       		CLASS(dma_map_single, dma)(dev,...;

	        ...
	        dmaengine_submit();
		if (...)
			return err;

		//before return;

		retain_and_empty(dma)
	}

This series just show how to hanndle many agurement at resource alloc/free
functions. Only show dma_map_single. If the over all method is acceptable.
I will more define for dma mapping functions.

Signed-off-by: Frank Li <Frank.Li at nxp.com>
---
Frank Li (3):
      cleanup: Add DEFINE_GUARD_ARGS_CLASS macro for resource alloc/free functions with multiple arguments
      dma-mapping: Add auto cleanup support dma_map_single()
      i2c: lpi2c: Use auto cleanup for dma_map_single()

 drivers/i2c/busses/i2c-imx-lpi2c.c | 13 ++++---
 include/linux/cleanup.h            | 73 ++++++++++++++++++++++++++++++++++++++
 include/linux/dma-mapping.h        |  8 +++++
 3 files changed, 87 insertions(+), 7 deletions(-)
---
base-commit: 7c3ba4249a3604477ea9c077e10089ba7ddcaa03
change-id: 20251008-dmamap_cleanup-d0a7f0525a3d

Best regards,
--
Frank Li <Frank.Li at nxp.com>