linux-kernel - [PATCH 2/7] of: factor out of_map

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Message-Id: <20260126-kaanapali-iris-v1-2-e2646246bfc1@oss.qualcomm.com>
Date: Mon, 26 Jan 2026 17:55:45 +0530
From: Vikash Garodia <vikash.garodia@....qualcomm.com>
To: Dikshita Agarwal <dikshita.agarwal@....qualcomm.com>,
        Abhinav Kumar <abhinav.kumar@...ux.dev>,
        Bryan O'Donoghue <bod@...nel.org>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Saravana Kannan <saravanak@...nel.org>, Joerg Roedel <joro@...tes.org>,
        Will Deacon <will@...nel.org>, Robin Murphy <robin.murphy@....com>,
        Stefan Schmidt <stefan.schmidt@...aro.org>,
        Hans Verkuil <hverkuil@...nel.org>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Vishnu Reddy <busanna.reddy@....qualcomm.com>,
        Hans Verkuil <hverkuil+cisco@...nel.org>
Cc: linux-arm-msm@...r.kernel.org, linux-media@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        iommu@...ts.linux.dev, Bryan O'Donoghue <bryan.odonoghue@...aro.org>,
        Vikash Garodia <vikash.garodia@....qualcomm.com>,
        Charan Teja Kalla <charan.kalla@....qualcomm.com>,
        Vijayanand Jitta <vijayanand.jitta@....qualcomm.com>
Subject: [PATCH 2/7] of: factor out of_map_id() code

From: Charan Teja Kalla <charan.kalla@....qualcomm.com>

Linux interprets multiple mappings for the same input ID as a set of
equivalent choices to pick one. There exists usecases where these set
must be maintained in parallel, ex: on ARM, a dynamically created child
device(s) is referencing multiple input id's in parent iommu-map.

Factor out the code where multiple mappings needs to be maintained in
parallel can be achieved through callback from this factored out code.

Signed-off-by: Charan Teja Kalla <charan.kalla@....qualcomm.com>
Signed-off-by: Vijayanand Jitta <vijayanand.jitta@....qualcomm.com>
Signed-off-by: Vikash Garodia <vikash.garodia@....qualcomm.com>
---
 drivers/of/base.c | 47 ++++++++++++++++++++++++++++++++---------------
 1 file changed, 32 insertions(+), 15 deletions(-)

diff --git a/drivers/of/base.c b/drivers/of/base.c
index 0825f3dc93f2472e9947af09acdde72031ab85bc..606bef4f90e7d13bae4f7b0c45acd1755ad89826 100644
--- a/drivers/of/base.c
+++ b/drivers/of/base.c
@@ -2122,6 +2122,32 @@ static bool of_check_bad_map(const __be32 *map, int len)
 	return true;
 }
 
+static int of_map_id_fill_output(struct of_map_id_arg *arg,
+				 struct device_node *phandle_node, u32 id_or_offset,
+				 const __be32 *out_base, u32 cells,
+				 bool bypass)
+{
+	if (bypass) {
+		arg->map_args.args[0] = id_or_offset;
+		return 0;
+	}
+
+	if (arg->map_args.np)
+		of_node_put(phandle_node);
+	else
+		arg->map_args.np = phandle_node;
+
+	if (arg->map_args.np != phandle_node)
+		return -EAGAIN;
+
+	for (int i = 0; i < cells; i++)
+		arg->map_args.args[i] = (id_or_offset + be32_to_cpu(out_base[i]));
+
+	arg->map_args.args_count = cells;
+
+	return 0;
+}
+
 /**
  * of_map_id - Translate an ID through a downstream mapping.
  * @np: root complex device node.
@@ -2162,8 +2188,7 @@ int of_map_id(const struct device_node *np, u32 id, const char *map_name,
 		if (arg->map_args.np)
 			return -ENODEV;
 		/* Otherwise, no map implies no translation */
-		arg->map_args.args[0] = id;
-		return 0;
+		goto bypass_translation;
 	}
 
 	if (map_bytes % sizeof(*map))
@@ -2185,6 +2210,7 @@ int of_map_id(const struct device_node *np, u32 id, const char *map_name,
 		struct device_node *phandle_node;
 		u32 id_base, phandle, id_len, id_off, cells = 0;
 		const __be32 *out_base;
+		int ret;
 
 		if (map_len - offset < 2)
 			goto err_map_len;
@@ -2238,19 +2264,10 @@ int of_map_id(const struct device_node *np, u32 id, const char *map_name,
 		if (masked_id < id_base || id_off >= id_len)
 			continue;
 
-		if (arg->map_args.np)
-			of_node_put(phandle_node);
-		else
-			arg->map_args.np = phandle_node;
-
-		if (arg->map_args.np != phandle_node)
+		ret = of_map_id_fill_output(arg, phandle_node, id_off, out_base, cells, false);
+		if (ret == -EAGAIN)
 			continue;
 
-		for (int i = 0; i < cells; i++)
-			arg->map_args.args[i] = (id_off + be32_to_cpu(out_base[i]));
-
-		arg->map_args.args_count = cells;
-
 		pr_debug("%pOF: %s, using mask %08x, id-base: %08x, out-base: %08x, length: %08x, id: %08x -> %08x\n",
 			np, map_name, map_mask, id_base, be32_to_cpup(out_base),
 			id_len, id, id_off + be32_to_cpup(out_base));
@@ -2260,9 +2277,9 @@ int of_map_id(const struct device_node *np, u32 id, const char *map_name,
 	pr_info("%pOF: no %s translation for id 0x%x on %pOF\n", np, map_name,
 		id, arg->map_args.np  ? arg->map_args.np : NULL);
 
+bypass_translation:
 	/* Bypasses translation */
-	arg->map_args.args[0] = id;
-	return 0;
+	return of_map_id_fill_output(arg, NULL, id, 0, 0, true);
 
 err_map_len:
 	pr_err("%pOF: Error: Bad %s length: %d\n", np, map_name, map_bytes);

-- 
2.34.1