linux-kernel - [PATCH v2] iommu: simplify list initialization in iommu_create_device_direct_mappings() and iommu_group_show_resv

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Message-Id: <20260112032116.49781-1-pengcan@kylinos.cn>
Date: Mon, 12 Jan 2026 11:21:16 +0800
From: Can Peng <pengcan@...inos.cn>
To: joro@...tes.org,
	will@...nel.org,
	robin.murphy@....com,
	Markus.Elfring@....de
Cc: iommu@...ts.linux.dev,
	linux-kernel@...r.kernel.org,
	Can Peng <pengcan@...inos.cn>
Subject: [PATCH v2] iommu: simplify list initialization in iommu_create_device_direct_mappings() and iommu_group_show_resv_regions()

Use LIST_HEAD() to declare and initialize list heads in both
iommu_create_device_direct_mappings() and iommu_group_show_resv_regions()
instead of separate declaration and INIT_LIST_HEAD(). This simplifies the
code by combining declaration and initialization into a single idiomatic
form, improving readability without changing functionality.

Signed-off-by: Can Peng <pengcan@...inos.cn>
---
>> Use LIST_HEAD() to declare and initialize the 'mappings' list head in
>> iommu_create_device_direct_mappings() instead of separate declaration and
>> INIT_LIST_HEAD(). This simplifies the code by combining declaration and
>> initialization into a single idiomatic form, improving readability without
>> changing functionality.
>…
>
>How do you think about to repeat the mentioned transformation approach for the implementation
>of the function “iommu_group_show_resv_regions”?
>https://elixir.bootlin.com/linux/v6.19-rc4/source/drivers/iommu/iommu.c#L949-L969
Changes since v1:
 - Extend the cleanup to iommu_group_show_resv_regions() as suggested by
   reviewer, applying the same LIST_HEAD() pattern consistently across
   the file.

Best regards,
Can Peng

 drivers/iommu/iommu.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index 2ca990dfbb88..b9ffd001b4b3 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -950,10 +950,9 @@ static ssize_t iommu_group_show_resv_regions(struct iommu_group *group,
 					     char *buf)
 {
 	struct iommu_resv_region *region, *next;
-	struct list_head group_resv_regions;
+	LIST_HEAD(group_resv_regions);
 	int offset = 0;
 
-	INIT_LIST_HEAD(&group_resv_regions);
 	iommu_get_group_resv_regions(group, &group_resv_regions);
 
 	list_for_each_entry_safe(region, next, &group_resv_regions, list) {
@@ -1173,12 +1172,11 @@ static int iommu_create_device_direct_mappings(struct iommu_domain *domain,
 					       struct device *dev)
 {
 	struct iommu_resv_region *entry;
-	struct list_head mappings;
+	LIST_HEAD(mappings);
 	unsigned long pg_size;
 	int ret = 0;
 
 	pg_size = domain->pgsize_bitmap ? 1UL << __ffs(domain->pgsize_bitmap) : 0;
-	INIT_LIST_HEAD(&mappings);
 
 	if (WARN_ON_ONCE(iommu_is_dma_domain(domain) && !pg_size))
 		return -EINVAL;
-- 
2.25.1