linux-kernel - [RFC PATCH 1/2] dmapool: Improve dma api kernel-doc comments

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Message-Id: <20241113063425.21042-2-yesanishhere@gmail.com>
Date: Tue, 12 Nov 2024 22:34:24 -0800
From: anish kumar <yesanishhere@...il.com>
To: corbet@....net,
	tj@...nel.org,
	akpm@...ux-foundation.org,
	ptesarik@...e.com,
	xavier_qy@....com,
	vbabka@...e.cz,
	tintinm2017@...il.com
Cc: linux-mm@...ck.org,
	linux-doc@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	anish kumar <yesanishhere@...il.com>
Subject: [RFC PATCH 1/2] dmapool: Improve dma api kernel-doc comments

Move explanatory content from the documentation
to source code comment written in kernel-doc format.
This allows kernel-doc to generate more comprehensive
and accurate documentation. Additionally, improving
the kernel-doc comment describes the api behaviour
and usage better.

Signed-off-by: anish kumar <yesanishhere@...il.com>
---
 mm/dmapool.c | 40 ++++++++++++++++++++++++++++------------
 1 file changed, 28 insertions(+), 12 deletions(-)

diff --git a/mm/dmapool.c b/mm/dmapool.c
index f0bfc6c490f4..8b32a52becd6 100644
--- a/mm/dmapool.c
+++ b/mm/dmapool.c
@@ -207,11 +207,16 @@ static void pool_block_push(struct dma_pool *pool, struct dma_block *block,
  * @boundary: returned blocks won't cross this power of two boundary
  * Context: not in_interrupt()
  *
- * Given one of these pools, dma_pool_alloc()
- * may be used to allocate memory.  Such memory will all have "consistent"
- * DMA mappings, accessible by the device and its driver without using
- * cache flushing primitives.  The actual size of blocks allocated may be
- * larger than requested because of alignment.
+ * This api initializes a pool of DMA-coherent buffers for use with a given
+ * device. It must be called in a context which can sleep. The device's
+ * hardware alignment requirement for this type of data is "align". If your
+ * device has no boundary crossing restrictions, pass 0 for alloc; passing
+ * 4096 says memory allocated from this pool must not cross 4KByte boundaries.
+ *
+ * Given one of these pools, dma_pool_alloc() may be used to allocate memory.
+ * Such memory will all have "consistent" DMA mappings, accessible by the
+ * device and its driver without using cache flushing primitives.  The actual
+ * size of blocks allocated may be larger than requested because of alignment.
  *
  * If @boundary is nonzero, objects returned from dma_pool_alloc() won't
  * cross that size boundary.  This is useful for devices which have
@@ -356,6 +361,7 @@ static struct dma_page *pool_alloc_page(struct dma_pool *pool, gfp_t mem_flags)
  *
  * Caller guarantees that no more memory from the pool is in use,
  * and that nothing will try to use the pool after this call.
+ * It must be called in a context which can sleep.
  */
 void dma_pool_destroy(struct dma_pool *pool)
 {
@@ -392,14 +398,24 @@ void dma_pool_destroy(struct dma_pool *pool)
 EXPORT_SYMBOL(dma_pool_destroy);
 
 /**
- * dma_pool_alloc - get a block of consistent memory
- * @pool: dma pool that will produce the block
- * @mem_flags: GFP_* bitmask
- * @handle: pointer to dma address of block
+ * dma_pool_alloc - Get a block of consistent memory from a DMA pool
+ * @pool:       DMA pool that will produce the block
+ * @mem_flags:  GFP_* bitmask specifying memory allocation flags
+ * @handle:     Pointer to a DMA address that will hold the address of the block
+ *
+ * Return: The kernel virtual address of a currently unused block of memory,
+ *         and reports its DMA address through the handle. If such a memory
+ *         block can't be allocated, %NULL is returned.
+ *
+ * This function allocates memory from the specified DMA pool. The returned
+ * memory will meet the size and alignment requirements specified when the
+ * pool was created. Pass GFP_ATOMIC to prevent blocking, or if permitted
+ * (not in interrupt context, and not holding SMP locks), pass GFP_KERNEL
+ * to allow blocking.
  *
- * Return: the kernel virtual address of a currently unused block,
- * and reports its dma address through the handle.
- * If such a memory block can't be allocated, %NULL is returned.
+ * Similar to dma_alloc_coherent(), this function returns two addresses:
+ *  - A CPU-accessible virtual address
+ *  - A DMA address usable by the pool's associated device.
  */
 void *dma_pool_alloc(struct dma_pool *pool, gfp_t mem_flags,
 		     dma_addr_t *handle)
-- 
2.39.5 (Apple Git-154)