Subject: [PATCH v4 10/12] crypto: atmel-i2c - implement capability-based client selection

From: Lothar Rubusch <[email-masked]>
Date: Fri, 22 May 2026 23:01:32 +0000

Extend the shared I2C client allocation interface to support feature-aware
hardware selection by introducing capability filtering.

Add a 'caps' mask to 'struct atmel_i2c_client_priv' alongside an
'atmel_i2c_capability' enum. The allocator now explicitly filters hardware
nodes by a requested capability bit while retaining the least-loaded device
load-balancing scheme.

Update the ECC driver to advertise ATMEL_CAP_ECDH configuration capability
during probe, and adapt the tfm context setup execution path to request
this specific capability variant. Initialize the bitmask field to zero
inside the SHA204A driver context for now.

Signed-off-by: Lothar Rubusch <[email-masked]>
---
 drivers/crypto/atmel-ecc.c     | 4 +++-
 drivers/crypto/atmel-i2c.c     | 6 +++++-
 drivers/crypto/atmel-i2c.h     | 8 +++++++-
 drivers/crypto/atmel-sha204a.c | 2 ++
 4 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/drivers/crypto/atmel-ecc.c b/drivers/crypto/atmel-ecc.c
index 16e607cd06c4..76b8f9e7c2e1 100644
--- a/drivers/crypto/atmel-ecc.c
+++ b/drivers/crypto/atmel-ecc.c
@@ -212,7 +212,7 @@ static int atmel_ecdh_init_tfm(struct crypto_kpp *tfm)
 	struct atmel_ecdh_ctx *ctx = kpp_tfm_ctx(tfm);
 
 	ctx->curve_id = ECC_CURVE_NIST_P256;
-	ctx->client = atmel_i2c_client_alloc();
+	ctx->client = atmel_i2c_client_alloc(ATMEL_CAP_ECDH);
 	if (IS_ERR(ctx->client)) {
 		pr_err("tfm - i2c_client binding failed\n");
 		return PTR_ERR(ctx->client);
@@ -287,6 +287,8 @@ static int atmel_ecc_probe(struct i2c_client *client)
 	i2c_priv = i2c_get_clientdata(client);
 	i2c_priv->ready = false;
 
+	i2c_priv->caps = BIT(ATMEL_CAP_ECDH);
+
 	spin_lock(&atmel_i2c_mgmt.i2c_list_lock);
 	list_add_tail(&i2c_priv->i2c_client_list_node,
 		      &atmel_i2c_mgmt.i2c_client_list);
diff --git a/drivers/crypto/atmel-i2c.c b/drivers/crypto/atmel-i2c.c
index 92d3e28f9d9a..4953b8fcb02d 100644
--- a/drivers/crypto/atmel-i2c.c
+++ b/drivers/crypto/atmel-i2c.c
@@ -57,7 +57,7 @@ static void atmel_i2c_checksum(struct atmel_i2c_cmd *cmd)
 	*__crc16 = cpu_to_le16(bitrev16(crc16(0, data, len)));
 }
 
-struct i2c_client *atmel_i2c_client_alloc(void)
+struct i2c_client *atmel_i2c_client_alloc(enum atmel_i2c_capability cap)
 {
 	struct atmel_i2c_client_priv *i2c_priv, *min_i2c_priv = NULL;
 	struct i2c_client *client = ERR_PTR(-ENODEV);
@@ -75,6 +75,10 @@ struct i2c_client *atmel_i2c_client_alloc(void)
 			    i2c_client_list_node) {
 		if (!i2c_priv->ready)
 			continue;
+
+		if (!(i2c_priv->caps & BIT(cap)))
+			continue;
+
 		tfm_cnt = atomic_read(&i2c_priv->tfm_count);
 		if (tfm_cnt < min_tfm_cnt) {
 			min_tfm_cnt = tfm_cnt;
diff --git a/drivers/crypto/atmel-i2c.h b/drivers/crypto/atmel-i2c.h
index ddab80bc1a72..af2e49332ab6 100644
--- a/drivers/crypto/atmel-i2c.h
+++ b/drivers/crypto/atmel-i2c.h
@@ -115,6 +115,10 @@ struct atmel_i2c_cmd {
 #define ECDH_PREFIX_MODE		0x00
 
 /* Used for binding tfm objects to i2c clients. */
+enum atmel_i2c_capability {
+	ATMEL_CAP_ECDH = 0,
+};
+
 struct atmel_i2c_client_mgmt {
 	struct list_head i2c_client_list;
 	spinlock_t i2c_list_lock;
@@ -131,6 +135,7 @@ extern struct atmel_i2c_client_mgmt atmel_i2c_mgmt;
  * @tfm_count           : number of active crypto transformations on i2c client
  * @hwrng               : hold the hardware generated rng
  * @ready               : hw client is ready to use
+ * @caps                : feature capability of the particular driver
  *
  * Reads and writes from/to the i2c client are sequential. The first byte
  * transmitted to the device is treated as the byte size. Any attempt to send
@@ -149,6 +154,7 @@ struct atmel_i2c_client_priv {
 	struct hwrng hwrng;
 	struct completion remove_done;
 	bool ready;
+	u32 caps;
 };
 
 /**
@@ -193,7 +199,7 @@ void atmel_i2c_init_genkey_cmd(struct atmel_i2c_cmd *cmd, u16 keyid);
 int atmel_i2c_init_ecdh_cmd(struct atmel_i2c_cmd *cmd,
 			    struct scatterlist *pubkey);
 
-struct i2c_client *atmel_i2c_client_alloc(void);
+struct i2c_client *atmel_i2c_client_alloc(enum atmel_i2c_capability cap);
 void atmel_i2c_client_free(struct i2c_client *client);
 
 void atmel_i2c_deactivate_client(struct atmel_i2c_client_priv *i2c_priv);
diff --git a/drivers/crypto/atmel-sha204a.c b/drivers/crypto/atmel-sha204a.c
index 33e5a66b843c..0c5b5cdbfcbc 100644
--- a/drivers/crypto/atmel-sha204a.c
+++ b/drivers/crypto/atmel-sha204a.c
@@ -178,6 +178,8 @@ static int atmel_sha204a_probe(struct i2c_client *client)
 
 	i2c_priv = i2c_get_clientdata(client);
 
+	i2c_priv->caps = 0;
+
 	memset(&i2c_priv->hwrng, 0, sizeof(i2c_priv->hwrng));
 
 	i2c_priv->hwrng.name = dev_name(&client->dev);
-- 
2.39.5