1 files changed, 153 insertions, 227 deletions

diff --git a/drivers/firmware/turris-mox-rwtm.c b/drivers/firmware/turris-mox-rwtm.c
index 3e7f186d239a..525ebdc7ded5 100644
--- a/drivers/firmware/turris-mox-rwtm.c
+++ b/drivers/firmware/turris-mox-rwtm.c
@@ -5,26 +5,43 @@
  * Copyright (C) 2019, 2024 Marek Behún <kabel@kernel.org>
  */
 
+#include <crypto/sha2.h>
+#include <linux/align.h>
 #include <linux/armada-37xx-rwtm-mailbox.h>
 #include <linux/completion.h>
+#include <linux/container_of.h>
 #include <linux/debugfs.h>
+#include <linux/device.h>
 #include <linux/dma-mapping.h>
+#include <linux/err.h>
+#include <linux/fs.h>
 #include <linux/hw_random.h>
+#include <linux/if_ether.h>
+#include <linux/kobject.h>
 #include <linux/mailbox_client.h>
+#include <linux/minmax.h>
 #include <linux/module.h>
 #include <linux/mutex.h>
-#include <linux/of.h>
 #include <linux/platform_device.h>
-#include <linux/slab.h>
+#include <linux/sizes.h>
+#include <linux/sysfs.h>
+#include <linux/types.h>
 
 #define DRIVER_NAME		"turris-mox-rwtm"
 
+#define RWTM_DMA_BUFFER_SIZE	SZ_4K
+
 /*
  * The macros and constants below come from Turris Mox's rWTM firmware code.
  * This firmware is open source and it's sources can be found at
  * https://gitlab.labs.nic.cz/turris/mox-boot-builder/tree/master/wtmi.
  */
 
+#define MOX_ECC_NUMBER_WORDS	17
+#define MOX_ECC_NUMBER_LEN	(MOX_ECC_NUMBER_WORDS * sizeof(u32))
+
+#define MOX_ECC_SIGNATURE_WORDS	(2 * MOX_ECC_NUMBER_WORDS)
+
 #define MBOX_STS_SUCCESS	(0 << 30)
 #define MBOX_STS_FAIL		(1 << 30)
 #define MBOX_STS_BADCMD		(2 << 30)
@@ -44,13 +61,9 @@ enum mbox_cmd {
 	MBOX_CMD_OTP_WRITE	= 8,
 };
 
-struct mox_kobject;
-
 struct mox_rwtm {
-	struct device *dev;
 	struct mbox_client mbox_client;
 	struct mbox_chan *mbox;
-	struct mox_kobject *kobj;
 	struct hwrng hwrng;
 
 	struct armada_37xx_rwtm_rx_msg reply;
@@ -62,13 +75,13 @@ struct mox_rwtm {
 	struct completion cmd_done;
 
 	/* board information */
-	int has_board_info;
+	bool has_board_info;
 	u64 serial_number;
 	int board_version, ram_size;
-	u8 mac_address1[6], mac_address2[6];
+	u8 mac_address1[ETH_ALEN], mac_address2[ETH_ALEN];
 
 	/* public key burned in eFuse */
-	int has_pubkey;
+	bool has_pubkey;
 	u8 pubkey[135];
 
 #ifdef CONFIG_DEBUG_FS
@@ -78,65 +91,27 @@ struct mox_rwtm {
 	 * It should be rewritten via crypto API once akcipher API is available
 	 * from userspace.
 	 */
-	struct dentry *debugfs_root;
-	u32 last_sig[34];
-	int last_sig_done;
+	u32 last_sig[MOX_ECC_SIGNATURE_WORDS];
+	bool last_sig_done;
 #endif
 };
 
-struct mox_kobject {
-	struct kobject kobj;
-	struct mox_rwtm *rwtm;
-};
-
-static inline struct kobject *rwtm_to_kobj(struct mox_rwtm *rwtm)
-{
-	return &rwtm->kobj->kobj;
-}
-
-static inline struct mox_rwtm *to_rwtm(struct kobject *kobj)
-{
-	return container_of(kobj, struct mox_kobject, kobj)->rwtm;
-}
-
-static void mox_kobj_release(struct kobject *kobj)
-{
-	kfree(to_rwtm(kobj)->kobj);
-}
-
-static const struct kobj_type mox_kobj_ktype = {
-	.release	= mox_kobj_release,
-	.sysfs_ops	= &kobj_sysfs_ops,
-};
-
-static int mox_kobj_create(struct mox_rwtm *rwtm)
+static inline struct device *rwtm_dev(struct mox_rwtm *rwtm)
 {
-	rwtm->kobj = kzalloc(sizeof(*rwtm->kobj), GFP_KERNEL);
-	if (!rwtm->kobj)
-		return -ENOMEM;
-
-	kobject_init(rwtm_to_kobj(rwtm), &mox_kobj_ktype);
-	if (kobject_add(rwtm_to_kobj(rwtm), firmware_kobj, "turris-mox-rwtm")) {
-		kobject_put(rwtm_to_kobj(rwtm));
-		return -ENXIO;
-	}
-
-	rwtm->kobj->rwtm = rwtm;
-
-	return 0;
+	return rwtm->mbox_client.dev;
 }
 
 #define MOX_ATTR_RO(name, format, cat)				\
 static ssize_t							\
-name##_show(struct kobject *kobj, struct kobj_attribute *a,	\
+name##_show(struct device *dev, struct device_attribute *a,	\
 	    char *buf)						\
 {								\
-	struct mox_rwtm *rwtm = to_rwtm(kobj);	\
+	struct mox_rwtm *rwtm = dev_get_drvdata(dev);		\
 	if (!rwtm->has_##cat)					\
 		return -ENODATA;				\
-	return sprintf(buf, format, rwtm->name);		\
+	return sysfs_emit(buf, format, rwtm->name);		\
 }								\
-static struct kobj_attribute mox_attr_##name = __ATTR_RO(name)
+static DEVICE_ATTR_RO(name)
 
 MOX_ATTR_RO(serial_number, "%016llX\n", board_info);
 MOX_ATTR_RO(board_version, "%i\n", board_info);
@@ -145,6 +120,17 @@ MOX_ATTR_RO(mac_address1, "%pM\n", board_info);
 MOX_ATTR_RO(mac_address2, "%pM\n", board_info);
 MOX_ATTR_RO(pubkey, "%s\n", pubkey);
 
+static struct attribute *turris_mox_rwtm_attrs[] = {
+	&dev_attr_serial_number.attr,
+	&dev_attr_board_version.attr,
+	&dev_attr_ram_size.attr,
+	&dev_attr_mac_address1.attr,
+	&dev_attr_mac_address2.attr,
+	&dev_attr_pubkey.attr,
+	NULL
+};
+ATTRIBUTE_GROUPS(turris_mox_rwtm);
+
 static int mox_get_status(enum mbox_cmd cmd, u32 retval)
 {
 	if (MBOX_STS_CMD(retval) != cmd)
@@ -152,23 +138,13 @@ static int mox_get_status(enum mbox_cmd cmd, u32 retval)
 	else if (MBOX_STS_ERROR(retval) == MBOX_STS_FAIL)
 		return -(int)MBOX_STS_VALUE(retval);
 	else if (MBOX_STS_ERROR(retval) == MBOX_STS_BADCMD)
-		return -ENOSYS;
+		return -EOPNOTSUPP;
 	else if (MBOX_STS_ERROR(retval) != MBOX_STS_SUCCESS)
 		return -EIO;
 	else
 		return MBOX_STS_VALUE(retval);
 }
 
-static const struct attribute *mox_rwtm_attrs[] = {
-	&mox_attr_serial_number.attr,
-	&mox_attr_board_version.attr,
-	&mox_attr_ram_size.attr,
-	&mox_attr_mac_address1.attr,
-	&mox_attr_mac_address2.attr,
-	&mox_attr_pubkey.attr,
-	NULL
-};
-
 static void mox_rwtm_rx_callback(struct mbox_client *cl, void *data)
 {
 	struct mox_rwtm *rwtm = dev_get_drvdata(cl->dev);
@@ -181,6 +157,34 @@ static void mox_rwtm_rx_callback(struct mbox_client *cl, void *data)
 	complete(&rwtm->cmd_done);
 }
 
+static int mox_rwtm_exec(struct mox_rwtm *rwtm, enum mbox_cmd cmd,
+			 struct armada_37xx_rwtm_tx_msg *msg,
+			 bool interruptible)
+{
+	struct armada_37xx_rwtm_tx_msg _msg = {};
+	int ret;
+
+	if (!msg)
+		msg = &_msg;
+
+	msg->command = cmd;
+
+	ret = mbox_send_message(rwtm->mbox, msg);
+	if (ret < 0)
+		return ret;
+
+	if (interruptible) {
+		ret = wait_for_completion_interruptible(&rwtm->cmd_done);
+		if (ret < 0)
+			return ret;
+	} else {
+		if (!wait_for_completion_timeout(&rwtm->cmd_done, HZ / 2))
+			return -ETIMEDOUT;
+	}
+
+	return mox_get_status(cmd, rwtm->reply.retval);
+}
+
 static void reply_to_mac_addr(u8 *mac, u32 t1, u32 t2)
 {
 	mac[0] = t1 >> 8;
@@ -193,24 +197,16 @@ static void reply_to_mac_addr(u8 *mac, u32 t1, u32 t2)
 
 static int mox_get_board_info(struct mox_rwtm *rwtm)
 {
-	struct armada_37xx_rwtm_tx_msg msg;
+	struct device *dev = rwtm_dev(rwtm);
 	struct armada_37xx_rwtm_rx_msg *reply = &rwtm->reply;
 	int ret;
 
-	msg.command = MBOX_CMD_BOARD_INFO;
-	ret = mbox_send_message(rwtm->mbox, &msg);
-	if (ret < 0)
-		return ret;
-
-	if (!wait_for_completion_timeout(&rwtm->cmd_done, HZ / 2))
-		return -ETIMEDOUT;
-
-	ret = mox_get_status(MBOX_CMD_BOARD_INFO, reply->retval);
+	ret = mox_rwtm_exec(rwtm, MBOX_CMD_BOARD_INFO, NULL, false);
 	if (ret == -ENODATA) {
-		dev_warn(rwtm->dev,
+		dev_warn(dev,
 			 "Board does not have manufacturing information burned!\n");
-	} else if (ret == -ENOSYS) {
-		dev_notice(rwtm->dev,
+	} else if (ret == -EOPNOTSUPP) {
+		dev_notice(dev,
 			   "Firmware does not support the BOARD_INFO command\n");
 	} else if (ret < 0) {
 		return ret;
@@ -224,7 +220,7 @@ static int mox_get_board_info(struct mox_rwtm *rwtm)
 				  reply->status[5]);
 		reply_to_mac_addr(rwtm->mac_address2, reply->status[6],
 				  reply->status[7]);
-		rwtm->has_board_info = 1;
+		rwtm->has_board_info = true;
 
 		pr_info("Turris Mox serial number %016llX\n",
 			rwtm->serial_number);
@@ -232,26 +228,18 @@ static int mox_get_board_info(struct mox_rwtm *rwtm)
 		pr_info("           burned RAM size %i MiB\n", rwtm->ram_size);
 	}
 
-	msg.command = MBOX_CMD_ECDSA_PUB_KEY;
-	ret = mbox_send_message(rwtm->mbox, &msg);
-	if (ret < 0)
-		return ret;
-
-	if (!wait_for_completion_timeout(&rwtm->cmd_done, HZ / 2))
-		return -ETIMEDOUT;
-
-	ret = mox_get_status(MBOX_CMD_ECDSA_PUB_KEY, reply->retval);
+	ret = mox_rwtm_exec(rwtm, MBOX_CMD_ECDSA_PUB_KEY, NULL, false);
 	if (ret == -ENODATA) {
-		dev_warn(rwtm->dev, "Board has no public key burned!\n");
-	} else if (ret == -ENOSYS) {
-		dev_notice(rwtm->dev,
+		dev_warn(dev, "Board has no public key burned!\n");
+	} else if (ret == -EOPNOTSUPP) {
+		dev_notice(dev,
 			   "Firmware does not support the ECDSA_PUB_KEY command\n");
 	} else if (ret < 0) {
 		return ret;
 	} else {
 		u32 *s = reply->status;
 
-		rwtm->has_pubkey = 1;
+		rwtm->has_pubkey = true;
 		sprintf(rwtm->pubkey,
 			"%06x%08x%08x%08x%08x%08x%08x%08x%08x%08x%08x%08x%08x%08x%08x%08x%08x",
 			ret, s[0], s[1], s[2], s[3], s[4], s[5], s[6], s[7],
@@ -263,37 +251,22 @@ static int mox_get_board_info(struct mox_rwtm *rwtm)
 
 static int check_get_random_support(struct mox_rwtm *rwtm)
 {
-	struct armada_37xx_rwtm_tx_msg msg;
-	int ret;
+	struct armada_37xx_rwtm_tx_msg msg = {
+		.args = { 1, rwtm->buf_phys, 4 },
+	};
 
-	msg.command = MBOX_CMD_GET_RANDOM;
-	msg.args[0] = 1;
-	msg.args[1] = rwtm->buf_phys;
-	msg.args[2] = 4;
-
-	ret = mbox_send_message(rwtm->mbox, &msg);
-	if (ret < 0)
-		return ret;
-
-	if (!wait_for_completion_timeout(&rwtm->cmd_done, HZ / 2))
-		return -ETIMEDOUT;
-
-	return mox_get_status(MBOX_CMD_GET_RANDOM, rwtm->reply.retval);
+	return mox_rwtm_exec(rwtm, MBOX_CMD_GET_RANDOM, &msg, false);
 }
 
 static int mox_hwrng_read(struct hwrng *rng, void *data, size_t max, bool wait)
 {
-	struct mox_rwtm *rwtm = (struct mox_rwtm *) rng->priv;
-	struct armada_37xx_rwtm_tx_msg msg;
+	struct mox_rwtm *rwtm = container_of(rng, struct mox_rwtm, hwrng);
+	struct armada_37xx_rwtm_tx_msg msg = {
+		.args = { 1, rwtm->buf_phys, ALIGN(max, 4) },
+	};
 	int ret;
 
-	if (max > 4096)
-		max = 4096;
-
-	msg.command = MBOX_CMD_GET_RANDOM;
-	msg.args[0] = 1;
-	msg.args[1] = rwtm->buf_phys;
-	msg.args[2] = (max + 3) & ~3;
+	max = min(max, RWTM_DMA_BUFFER_SIZE);
 
 	if (!wait) {
 		if (!mutex_trylock(&rwtm->busy))
@@ -302,15 +275,7 @@ static int mox_hwrng_read(struct hwrng *rng, void *data, size_t max, bool wait)
 		mutex_lock(&rwtm->busy);
 	}
 
-	ret = mbox_send_message(rwtm->mbox, &msg);
-	if (ret < 0)
-		goto unlock_mutex;
-
-	ret = wait_for_completion_interruptible(&rwtm->cmd_done);
-	if (ret < 0)
-		goto unlock_mutex;
-
-	ret = mox_get_status(MBOX_CMD_GET_RANDOM, rwtm->reply.retval);
+	ret = mox_rwtm_exec(rwtm, MBOX_CMD_GET_RANDOM, &msg, true);
 	if (ret < 0)
 		goto unlock_mutex;
 
@@ -336,19 +301,19 @@ static ssize_t do_sign_read(struct file *file, char __user *buf, size_t len,
 	struct mox_rwtm *rwtm = file->private_data;
 	ssize_t ret;
 
-	/* only allow one read, of 136 bytes, from position 0 */
+	/* only allow one read, of whole signature, from position 0 */
 	if (*ppos != 0)
 		return 0;
 
-	if (len < 136)
+	if (len < sizeof(rwtm->last_sig))
 		return -EINVAL;
 
 	if (!rwtm->last_sig_done)
 		return -ENODATA;
 
-	/* 2 arrays of 17 32-bit words are 136 bytes */
-	ret = simple_read_from_buffer(buf, len, ppos, rwtm->last_sig, 136);
-	rwtm->last_sig_done = 0;
+	ret = simple_read_from_buffer(buf, len, ppos, rwtm->last_sig,
+				      sizeof(rwtm->last_sig));
+	rwtm->last_sig_done = false;
 
 	return ret;
 }
@@ -357,13 +322,11 @@ static ssize_t do_sign_write(struct file *file, const char __user *buf,
 			     size_t len, loff_t *ppos)
 {
 	struct mox_rwtm *rwtm = file->private_data;
-	struct armada_37xx_rwtm_rx_msg *reply = &rwtm->reply;
 	struct armada_37xx_rwtm_tx_msg msg;
 	loff_t dummy = 0;
 	ssize_t ret;
 
-	/* the input is a SHA-512 hash, so exactly 64 bytes have to be read */
-	if (len != 64)
+	if (len != SHA512_DIGEST_SIZE)
 		return -EINVAL;
 
 	/* if last result is not zero user has not read that information yet */
@@ -384,37 +347,32 @@ static ssize_t do_sign_write(struct file *file, const char __user *buf,
 	 *   3. Address of the buffer where ECDSA signature value S shall be
 	 *      stored by the rWTM firmware.
 	 */
-	memset(rwtm->buf, 0, 4);
-	ret = simple_write_to_buffer(rwtm->buf + 4, 64, &dummy, buf, len);
+	memset(rwtm->buf, 0, sizeof(u32));
+	ret = simple_write_to_buffer(rwtm->buf + sizeof(u32),
+				     SHA512_DIGEST_SIZE, &dummy, buf, len);
 	if (ret < 0)
 		goto unlock_mutex;
-	be32_to_cpu_array(rwtm->buf, rwtm->buf, 17);
+	be32_to_cpu_array(rwtm->buf, rwtm->buf, MOX_ECC_NUMBER_WORDS);
 
-	msg.command = MBOX_CMD_SIGN;
 	msg.args[0] = 1;
 	msg.args[1] = rwtm->buf_phys;
-	msg.args[2] = rwtm->buf_phys + 68;
-	msg.args[3] = rwtm->buf_phys + 2 * 68;
-	ret = mbox_send_message(rwtm->mbox, &msg);
-	if (ret < 0)
-		goto unlock_mutex;
+	msg.args[2] = rwtm->buf_phys + MOX_ECC_NUMBER_LEN;
+	msg.args[3] = rwtm->buf_phys + 2 * MOX_ECC_NUMBER_LEN;
 
-	ret = wait_for_completion_interruptible(&rwtm->cmd_done);
+	ret = mox_rwtm_exec(rwtm, MBOX_CMD_SIGN, &msg, true);
 	if (ret < 0)
 		goto unlock_mutex;
 
-	ret = MBOX_STS_VALUE(reply->retval);
-	if (MBOX_STS_ERROR(reply->retval) != MBOX_STS_SUCCESS)
-		goto unlock_mutex;
-
 	/*
 	 * Here we read the R and S values of the ECDSA signature
 	 * computed by the rWTM firmware and convert their words from
 	 * LE to BE.
 	 */
-	memcpy(rwtm->last_sig, rwtm->buf + 68, 136);
-	cpu_to_be32_array(rwtm->last_sig, rwtm->last_sig, 34);
-	rwtm->last_sig_done = 1;
+	memcpy(rwtm->last_sig, rwtm->buf + MOX_ECC_NUMBER_LEN,
+	       sizeof(rwtm->last_sig));
+	cpu_to_be32_array(rwtm->last_sig, rwtm->last_sig,
+			  MOX_ECC_SIGNATURE_WORDS);
+	rwtm->last_sig_done = true;
 
 	mutex_unlock(&rwtm->busy);
 	return len;
@@ -431,42 +389,36 @@ static const struct file_operations do_sign_fops = {
 	.llseek	= no_llseek,
 };
 
-static int rwtm_register_debugfs(struct mox_rwtm *rwtm)
+static void rwtm_debugfs_release(void *root)
 {
-	struct dentry *root, *entry;
-
-	root = debugfs_create_dir("turris-mox-rwtm", NULL);
+	debugfs_remove_recursive(root);
+}
 
-	if (IS_ERR(root))
-		return PTR_ERR(root);
+static void rwtm_register_debugfs(struct mox_rwtm *rwtm)
+{
+	struct dentry *root;
 
-	entry = debugfs_create_file_unsafe("do_sign", 0600, root, rwtm,
-					   &do_sign_fops);
-	if (IS_ERR(entry))
-		goto err_remove;
+	root = debugfs_create_dir("turris-mox-rwtm", NULL);
 
-	rwtm->debugfs_root = root;
+	debugfs_create_file_unsafe("do_sign", 0600, root, rwtm, &do_sign_fops);
 
-	return 0;
-err_remove:
-	debugfs_remove_recursive(root);
-	return PTR_ERR(entry);
+	devm_add_action_or_reset(rwtm_dev(rwtm), rwtm_debugfs_release, root);
 }
-
-static void rwtm_unregister_debugfs(struct mox_rwtm *rwtm)
+#else
+static inline void rwtm_register_debugfs(struct mox_rwtm *rwtm)
 {
-	debugfs_remove_recursive(rwtm->debugfs_root);
 }
-#else
-static inline int rwtm_register_debugfs(struct mox_rwtm *rwtm)
+#endif
+
+static void rwtm_devm_mbox_release(void *mbox)
 {
-	return 0;
+	mbox_free_channel(mbox);
 }
 
-static inline void rwtm_unregister_debugfs(struct mox_rwtm *rwtm)
+static void rwtm_firmware_symlink_drop(void *parent)
 {
+	sysfs_remove_link(parent, DRIVER_NAME);
 }
-#endif
 
 static int turris_mox_rwtm_probe(struct platform_device *pdev)
 {
@@ -478,40 +430,30 @@ static int turris_mox_rwtm_probe(struct platform_device *pdev)
 	if (!rwtm)
 		return -ENOMEM;
 
-	rwtm->dev = dev;
-	rwtm->buf = dmam_alloc_coherent(dev, PAGE_SIZE, &rwtm->buf_phys,
-					GFP_KERNEL);
+	rwtm->buf = dmam_alloc_coherent(dev, RWTM_DMA_BUFFER_SIZE,
+					&rwtm->buf_phys, GFP_KERNEL);
 	if (!rwtm->buf)
 		return -ENOMEM;
 
-	ret = mox_kobj_create(rwtm);
-	if (ret < 0) {
-		dev_err(dev, "Cannot create turris-mox-rwtm kobject!\n");
-		return ret;
-	}
-
-	ret = sysfs_create_files(rwtm_to_kobj(rwtm), mox_rwtm_attrs);
-	if (ret < 0) {
-		dev_err(dev, "Cannot create sysfs files!\n");
-		goto put_kobj;
-	}
-
 	platform_set_drvdata(pdev, rwtm);
 
-	mutex_init(&rwtm->busy);
+	ret = devm_mutex_init(dev, &rwtm->busy);
+	if (ret)
+		return ret;
+
 	init_completion(&rwtm->cmd_done);
 
 	rwtm->mbox_client.dev = dev;
 	rwtm->mbox_client.rx_callback = mox_rwtm_rx_callback;
 
 	rwtm->mbox = mbox_request_channel(&rwtm->mbox_client, 0);
-	if (IS_ERR(rwtm->mbox)) {
-		ret = PTR_ERR(rwtm->mbox);
-		if (ret != -EPROBE_DEFER)
-			dev_err(dev, "Cannot request mailbox channel: %i\n",
-				ret);
-		goto remove_files;
-	}
+	if (IS_ERR(rwtm->mbox))
+		return dev_err_probe(dev, PTR_ERR(rwtm->mbox),
+				     "Cannot request mailbox channel!\n");
+
+	ret = devm_add_action_or_reset(dev, rwtm_devm_mbox_release, rwtm->mbox);
+	if (ret)
+		return ret;
 
 	ret = mox_get_board_info(rwtm);
 	if (ret < 0)
@@ -521,46 +463,30 @@ static int turris_mox_rwtm_probe(struct platform_device *pdev)
 	if (ret < 0) {
 		dev_notice(dev,
 			   "Firmware does not support the GET_RANDOM command\n");
-		goto free_channel;
+		return ret;
 	}
 
 	rwtm->hwrng.name = DRIVER_NAME "_hwrng";
 	rwtm->hwrng.read = mox_hwrng_read;
-	rwtm->hwrng.priv = (unsigned long) rwtm;
 
 	ret = devm_hwrng_register(dev, &rwtm->hwrng);
-	if (ret < 0) {
-		dev_err(dev, "Cannot register HWRNG: %i\n", ret);
-		goto free_channel;
-	}
+	if (ret)
+		return dev_err_probe(dev, ret, "Cannot register HWRNG!\n");
 
-	ret = rwtm_register_debugfs(rwtm);
-	if (ret < 0) {
-		dev_err(dev, "Failed creating debugfs entries: %i\n", ret);
-		goto free_channel;
-	}
+	rwtm_register_debugfs(rwtm);
 
 	dev_info(dev, "HWRNG successfully registered\n");
 
-	return 0;
-
-free_channel:
-	mbox_free_channel(rwtm->mbox);
-remove_files:
-	sysfs_remove_files(rwtm_to_kobj(rwtm), mox_rwtm_attrs);
-put_kobj:
-	kobject_put(rwtm_to_kobj(rwtm));
-	return ret;
-}
-
-static void turris_mox_rwtm_remove(struct platform_device *pdev)
-{
-	struct mox_rwtm *rwtm = platform_get_drvdata(pdev);
+	/*
+	 * For sysfs ABI compatibility, create symlink
+	 * /sys/firmware/turris-mox-rwtm to this device's sysfs directory.
+	 */
+	ret = sysfs_create_link(firmware_kobj, &dev->kobj, DRIVER_NAME);
+	if (!ret)
+		devm_add_action_or_reset(dev, rwtm_firmware_symlink_drop,
+					 firmware_kobj);
 
-	rwtm_unregister_debugfs(rwtm);
-	sysfs_remove_files(rwtm_to_kobj(rwtm), mox_rwtm_attrs);
-	kobject_put(rwtm_to_kobj(rwtm));
-	mbox_free_channel(rwtm->mbox);
+	return 0;
 }
 
 static const struct of_device_id turris_mox_rwtm_match[] = {
@@ -573,10 +499,10 @@ MODULE_DEVICE_TABLE(of, turris_mox_rwtm_match);
 
 static struct platform_driver turris_mox_rwtm_driver = {
 	.probe	= turris_mox_rwtm_probe,
-	.remove_new = turris_mox_rwtm_remove,
 	.driver	= {
 		.name		= DRIVER_NAME,
 		.of_match_table	= turris_mox_rwtm_match,
+		.dev_groups	= turris_mox_rwtm_groups,
 	},
 };
 module_platform_driver(turris_mox_rwtm_driver);