RE: [PATCH v5 5/8] char: rpmb: add RPMB simulation device

[Winkler, Tomas]

> 
> On Mon, Jul 18, 2016 at 11:27:50PM +0300, Tomas Winkler wrote:
> > This is a simple platform device used for testing the RPMB subsystem.
> >
> > The module currently supports two configuration options:
> > 1. max_wr_blks: for specifying max blocks that can be written in a
> > single command 2. daunits:  used to set storage capacity in 128K
> > units.
> >
> >
> > Signed-off-by: Tomas Winkler <tomas.winkler@xxxxxxxxx>
> > ---
> > V2: remove .owner setting, it is set automatically
> > V3: 1. Add shutdown handler (similar to ufshcd)
> >     2. Commit message fix
> > V4: Use select RPMB in Kconfg to ensure valid configuration.
> > V5: Revamp the code using the sequence command.
> >
> >  drivers/char/rpmb/Kconfig    |  10 +
> >  drivers/char/rpmb/Makefile   |   1 +
> >  drivers/char/rpmb/rpmb_sim.c | 668
> > +++++++++++++++++++++++++++++++++++++++++++
> >  3 files changed, 679 insertions(+)
> >  create mode 100644 drivers/char/rpmb/rpmb_sim.c
> >
> > diff --git a/drivers/char/rpmb/Kconfig b/drivers/char/rpmb/Kconfig
> > index 6794be9fcc5e..c21b3934249f 100644
> > --- a/drivers/char/rpmb/Kconfig
> > +++ b/drivers/char/rpmb/Kconfig
> > @@ -13,3 +13,13 @@ config RPMB_INTF_DEV
> >  	help
> >  	  Say yes here if you want to access RPMB from user space
> >  	  via character device interface /dev/rpmb%d
> > +
> > +
> > +config RPMB_SIM
> > +	tristate "RPMB partition device simulator"
> > +	default n
> > +	select RPMB
> > +	select CRYPTO_SHA256
> > +	select CRYPTO_HMAC
> > +	help
> > +	  RPMB partition simulator used for testing the RPMB subsystem
> > diff --git a/drivers/char/rpmb/Makefile b/drivers/char/rpmb/Makefile
> > index b5dc087b1299..81f924fd9a87 100644
> > --- a/drivers/char/rpmb/Makefile
> > +++ b/drivers/char/rpmb/Makefile
> > @@ -1,5 +1,6 @@
> >  obj-$(CONFIG_RPMB) += rpmb.o
> >  rpmb-objs += core.o
> >  rpmb-$(CONFIG_RPMB_INTF_DEV) += cdev.o
> > +obj-$(CONFIG_RPMB_SIM) += rpmb_sim.o
> >
> >  ccflags-y += -D__CHECK_ENDIAN__
> > diff --git a/drivers/char/rpmb/rpmb_sim.c
> > b/drivers/char/rpmb/rpmb_sim.c new file mode 100644 index
> > 000000000000..e33f6809ae2c
> > --- /dev/null
> > +++ b/drivers/char/rpmb/rpmb_sim.c
> > @@ -0,0 +1,668 @@
> >
> +/**************************************************************
> ******
> > +**********
> > + * This file is provided under a dual BSD/GPLv2 license.  When using
> > +or
> > + * redistributing this file, you may do so under either license.
> > + *
> > + * GPL LICENSE SUMMARY
> > + *
> > + * Copyright(c) 2016 Intel Corporation. All rights reserved.
> > + *
> > + * This program is free software; you can redistribute it and/or
> > +modify
> > + * it under the terms of version 2 of the GNU General Public License
> > +as
> > + * published by the Free Software Foundation.
> > + *
> > + * This program is distributed in the hope that it will be useful,
> > +but
> > + * WITHOUT ANY WARRANTY; without even the implied warranty of
> > + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> GNU
> > + * General Public License for more details.
> > + *
> > + * The full GNU General Public License is included in this
> > +distribution
> > + * in the file called LICENSE.GPL.
> > + *
> > + * Contact Information:
> > + *	Intel Corporation.
> > + *	linux-mei@xxxxxxxxxxxxxxx
> > + *	http://www.intel.com
> > + *
> > + * BSD LICENSE
> > + *
> > + * Copyright(c) 2016 Intel Corporation. All rights reserved.
> > + * All rights reserved.
> > + *
> > + * Redistribution and use in source and binary forms, with or without
> > + * modification, are permitted provided that the following conditions
> > + * are met:
> > + *
> > + *  * Redistributions of source code must retain the above copyright
> > + *    notice, this list of conditions and the following disclaimer.
> > + *  * Redistributions in binary form must reproduce the above copyright
> > + *    notice, this list of conditions and the following disclaimer in
> > + *    the documentation and/or other materials provided with the
> > + *    distribution.
> > + *  * Neither the name Intel Corporation nor the names of its
> > + *    contributors may be used to endorse or promote products derived
> > + *    from this software without specific prior written permission.
> > + *
> > + * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
> > +CONTRIBUTORS
> > + * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT
> NOT
> > + * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
> FITNESS
> > +FOR
> > + * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
> > +COPYRIGHT
> > + * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
> > +INCIDENTAL,
> > + * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
> NOT
> > + * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
> OF
> > +USE,
> > + * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
> AND ON
> > +ANY
> > + * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR
> > +TORT
> > + * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
> THE
> > +USE
> > + * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
> DAMAGE.
> > + *
> > +
> >
> +***************************************************************
> ******
> > +********/
> > +#include <linux/module.h>
> > +#include <linux/slab.h>
> > +#include <linux/platform_device.h>
> > +#include <linux/device.h>
> > +#include <crypto/hash.h>
> > +#include <linux/scatterlist.h>
> > +#include <linux/sizes.h>
> > +
> > +#include <linux/rpmb.h>
> > +
> > +static const char id[] = "RPMB:SIM";
> > +#define CAPACITY_UNIT SZ_128K
> > +#define CAPACITY_MIN  SZ_128K
> > +#define CAPACITY_MAX  SZ_16M
> > +#define BLK_UNIT      SZ_256
> > +
> > +static unsigned int max_wr_blks = 1;
> > +module_param(max_wr_blks, uint, 0644);
> MODULE_PARM_DESC(max_wr_blks,
> > +"max blocks that can be written in a single command (default: 1)");
> > +
> > +static unsigned int daunits = 1;
> > +module_param(daunits, uint, 0644);
> > +MODULE_PARM_DESC(daunits, "number of data area units of 128K
> > +(default: 1)");
> > +
> > +struct blk {
> > +	u8 data[BLK_UNIT];
> > +};
> > +
> > +/**
> > + * struct rpmb_sim_dev
> > + *
> > + * @dev:  back pointer to the platform device
> > + * @rdev: rpmb device
> > + * @auth_key: Authentication key register which is used to authenticate
> > + *            accesses when MAC is calculated;
> > + * @auth_key_set: true if auth key was set
> > + * @write_counter: Counter value for the total amount of successful
> > + *             authenticated data write requests made by the host.
> > + *             The initial value of this register after production is 00000000h.
> > + *             The value will be incremented by one along with each successful
> > + *             programming access. The value cannot be reset. After the
> counter
> > + *             has reached the maximum value of FFFFFFFFh,
> > + *             it will not be incremented anymore (overflow prevention)
> > + * @hash_tfm:  hmac(sha256) tfm
> > + *
> > + * @res_frames: frame that holds the result of the last write
> > +operation
> > + * @out_frames: next read operation result frames
> > + * @out_frames_cnt: number of the output frames
> > + *
> > + * @capacity: size of the partition in bytes multiple of 128K
> > + * @blkcnt:   block count
> > + * @da:       data area in blocks
> > + */
> > +struct rpmb_sim_dev {
> > +	struct device *dev;
> > +	struct rpmb_dev *rdev;
> > +	u8 auth_key[32];
> > +	bool auth_key_set;
> > +	u32 write_counter;
> > +	struct crypto_shash *hash_tfm;
> > +
> > +	struct rpmb_frame res_frames[1];
> > +	struct rpmb_frame *out_frames;
> > +	unsigned int out_frames_cnt;
> > +
> > +	size_t capacity;
> > +	size_t blkcnt;
> > +	struct blk *da;
> > +};
> > +
> > +static __be16 op_result(struct rpmb_sim_dev *rsdev, u16 result) {
> > +	if (!rsdev->auth_key_set)
> > +		return cpu_to_be16(RPMB_ERR_NO_KEY);
> > +
> > +	if (rsdev->write_counter == 0xFFFFFFFF)
> > +		result |=  RPMB_ERR_COUNTER_EXPIRED;
> > +
> > +	return cpu_to_be16(result);
> > +}
> > +
> > +static __be16 req_to_resp(u16 req)
> > +{
> > +	return cpu_to_be16(RPMB_REQ2RESP(req)); }
> > +
> > +static int rpmb_sim_calc_hmac(struct rpmb_sim_dev *rsdev,
> > +			      struct rpmb_frame *frames,
> > +			      unsigned int blks, u8 *mac)
> > +{
> > +	SHASH_DESC_ON_STACK(desc, rsdev->hash_tfm);
> > +	int i;
> > +	int ret;
> > +
> > +	desc->tfm = rsdev->hash_tfm;
> > +	desc->flags = 0;
> > +
> > +	ret = crypto_shash_init(desc);
> > +	if (ret)
> > +		goto out;
> > +
> > +	for (i = 0; i < blks; i++) {
> > +		ret = crypto_shash_update(desc, frames[i].data,
> hmac_data_len);
> > +		if (ret)
> > +			goto out;
> > +	}
> > +	ret = crypto_shash_final(desc, mac);
> > +out:
> > +	if (ret)
> > +		dev_err(rsdev->dev, "digest error = %d", ret);
> > +
> > +	return ret;
> > +}
> > +
> > +static int rpmb_op_not_programmed(struct rpmb_sim_dev *rsdev, u16
> > +req) {
> > +	struct rpmb_frame *res_frame = rsdev->res_frames;
> > +
> > +	res_frame->req_resp = req_to_resp(req);
> > +	res_frame->result = op_result(rsdev, RPMB_ERR_NO_KEY);
> > +
> > +	dev_err(rsdev->dev, "not programmed\n");
> > +
> > +	return 0;
> > +}
> > +
> > +static int rpmb_op_program_key(struct rpmb_sim_dev *rsdev,
> > +			       struct rpmb_frame *in_frame, u32 cnt) {
> > +	struct rpmb_frame *res_frame = rsdev->res_frames;
> > +	u16 req;
> > +	int ret;
> > +	u16 err = RPMB_ERR_OK;
> > +
> > +	req = be16_to_cpu(in_frame[0].req_resp);
> > +
> > +	if (req != RPMB_PROGRAM_KEY)
> > +		return -EINVAL;
> > +
> > +	if (cnt != 1)
> > +		return -EINVAL;
> > +
> > +	if (rsdev->auth_key_set) {
> > +		dev_err(rsdev->dev, "key allread set\n");
> > +		err = RPMB_ERR_WRITE;
> > +		goto out;
> > +	}
> > +
> > +	ret = crypto_shash_setkey(rsdev->hash_tfm, in_frame[0].key_mac,
> 32);
> > +	if (ret) {
> > +		dev_err(rsdev->dev, "set key failed = %d\n", ret);
> > +		err = RPMB_ERR_GENERAL;
> > +		goto out;
> > +	}
> > +
> > +	dev_dbg(rsdev->dev, "digest size %u\n",
> > +		crypto_shash_digestsize(rsdev->hash_tfm));
> > +
> > +	memcpy(rsdev->auth_key, in_frame[0].key_mac, 32);
> > +	rsdev->auth_key_set = true;
> > +out:
> > +
> > +	memset(res_frame, 0, sizeof(struct rpmb_frame));
> > +	res_frame->req_resp = req_to_resp(req);
> > +	res_frame->result = op_result(rsdev, err);
> > +
> > +	return 0;
> > +}
> > +
> > +static int rpmb_op_get_wr_counter(struct rpmb_sim_dev *rsdev,
> > +				  struct rpmb_frame *in_frame, u32 cnt) {
> > +	struct rpmb_frame *frame;
> > +	int ret = 0;
> > +	u16 req;
> > +	u16 err;
> > +
> > +	req = be16_to_cpu(in_frame[0].req_resp);
> > +	if (req != RPMB_GET_WRITE_COUNTER)
> > +		return -EINVAL;
> > +
> > +	if (cnt != 1)
> > +		return -EINVAL;
> > +
> > +	frame = kcalloc(1, sizeof(struct rpmb_frame), GFP_KERNEL);
> > +	if (!frame) {
> > +		err = RPMB_ERR_READ;
> > +		ret = -ENOMEM;
> > +		rsdev->out_frames = rsdev->res_frames;
> > +		rsdev->out_frames_cnt = cnt;
> > +		goto out;
> > +	}
> > +
> > +	rsdev->out_frames = frame;
> > +	rsdev->out_frames_cnt = cnt;
> > +
> > +	frame->req_resp = req_to_resp(req);
> > +	frame->write_counter = cpu_to_be32(rsdev->write_counter);
> > +	memcpy(frame->nonce, in_frame[0].nonce, 16);
> > +
> > +	err = RPMB_ERR_OK;
> > +	if (rpmb_sim_calc_hmac(rsdev, frame, cnt, frame->key_mac))
> > +		err = RPMB_ERR_READ;
> > +
> > +out:
> > +	rsdev->out_frames[0].req_resp = req_to_resp(req);
> > +	rsdev->out_frames[0].result = op_result(rsdev, err);
> > +
> > +	return ret;
> > +}
> > +
> > +static int rpmb_op_write_data(struct rpmb_sim_dev *rsdev,
> > +			      struct rpmb_frame *in_frame, u32 cnt) {
> > +	struct rpmb_frame *res_frame = rsdev->res_frames;
> > +	u8 mac[32];
> > +	u16 req, err, addr, blks;
> > +	unsigned int i;
> > +	int ret = 0;
> > +
> > +	req = be16_to_cpu(in_frame[0].req_resp);
> > +	if (req != RPMB_WRITE_DATA)
> > +		return -EINVAL;
> > +
> > +	if (rsdev->write_counter == 0xFFFFFFFF) {
> > +		err = RPMB_ERR_WRITE;
> > +		goto out;
> > +	}
> > +
> > +	blks = be16_to_cpu(in_frame[0].block_count);
> > +	if (blks == 0 || blks > cnt) {
> > +		ret = -EINVAL;
> > +		err = RPMB_ERR_GENERAL;
> > +		goto out;
> > +	}
> > +
> > +	if (blks > max_wr_blks) {
> > +		err = RPMB_ERR_WRITE;
> > +		goto out;
> > +	}
> > +
> > +	addr = be16_to_cpu(in_frame[0].addr);
> > +	if (addr >= rsdev->blkcnt) {
> > +		err = RPMB_ERR_ADDRESS;
> > +		goto out;
> > +	}
> > +
> > +	if (rpmb_sim_calc_hmac(rsdev, in_frame, blks, mac)) {
> > +		err = RPMB_ERR_AUTH;
> > +		goto out;
> > +	}
> > +
> > +	/* mac is in the last frame */
> > +	if (memcmp(mac, in_frame[blks - 1].key_mac, sizeof(mac)) != 0) {
> > +		err = RPMB_ERR_AUTH;
> > +		goto out;
> > +	}
> > +
> > +	if (be32_to_cpu(in_frame[0].write_counter) != rsdev->write_counter)
> {
> > +		err = RPMB_ERR_COUNTER;
> > +		goto out;
> > +	}
> > +
> > +	if (addr + blks > rsdev->blkcnt) {
> > +		err = RPMB_ERR_WRITE;
> > +		goto out;
> > +	}
> > +
> > +	err = RPMB_ERR_OK;
> > +	for (i = 0; i < blks; i++)
> > +		memcpy(rsdev->da[addr + i].data, in_frame[i].data,
> BLK_UNIT);
> > +
> > +	rsdev->write_counter++;
> > +
> > +out:
> > +	memset(res_frame, 0, sizeof(struct rpmb_frame));
> > +	if (err == RPMB_ERR_OK) {
> > +		res_frame->write_counter = cpu_to_be32(rsdev-
> >write_counter);
> > +		memcpy(res_frame->key_mac, mac, sizeof(mac));
> > +	}
> > +	res_frame->req_resp = req_to_resp(req);
> > +	res_frame->result = op_result(rsdev, err);
> > +
> > +	return ret;
> > +}
> > +
> > +static int rpmb_op_read_data(struct rpmb_sim_dev *rsdev,
> > +			     struct rpmb_frame *in_frame, u32 cnt) {
> > +	struct rpmb_frame *res_frame = rsdev->res_frames;
> > +	struct rpmb_frame *out_frame;
> > +	u8 mac[32];
> > +	u16 req, err, addr, blks;
> > +	unsigned int i;
> > +	int ret;
> > +
> > +	req = be16_to_cpu(in_frame[0].req_resp);
> > +	if (req != RPMB_READ_DATA)
> > +		return -EINVAL;
> > +
> > +	out_frame = kcalloc(cnt, sizeof(struct rpmb_frame), GFP_KERNEL);
> > +	if (!out_frame) {
> > +		ret = -ENOMEM;
> > +		err = RPMB_ERR_READ;
> > +		goto out;
> > +	}
> > +
> > +	blks = be16_to_cpu(in_frame[0].block_count);
> > +	if (blks == 0 || blks > cnt) {
> > +		ret = -EINVAL;
> > +		err = RPMB_ERR_READ;
> > +		goto out;
> > +	}
> > +
> > +	ret = 0;
> > +	addr = be16_to_cpu(in_frame[0].addr);
> > +	if (addr >= rsdev->blkcnt) {
> > +		err = RPMB_ERR_ADDRESS;
> > +		goto out;
> > +	}
> > +
> > +	if (addr + blks > rsdev->blkcnt) {
> > +		err = RPMB_ERR_READ;
> > +		goto out;
> > +	}
> > +
> > +	for (i = 0; i < blks; i++) {
> > +		memcpy(out_frame[i].data, rsdev->da[addr + i].data,
> BLK_UNIT);
> > +		memcpy(out_frame[i].nonce, in_frame[0].nonce, 16);
> > +		out_frame[i].req_resp = req_to_resp(req);
> > +		out_frame[i].addr = in_frame[0].addr;
> > +		out_frame[i].block_count = cpu_to_be16(blks);
> > +	}
> > +
> > +	if (rpmb_sim_calc_hmac(rsdev, out_frame, blks, mac)) {
> > +		err = RPMB_ERR_AUTH;
> > +		goto out;
> > +	}
> > +
> > +	memcpy(out_frame[blks - 1].key_mac, mac, sizeof(mac));
> > +
> > +	err = RPMB_ERR_OK;
> > +	out_frame[0].result = op_result(rsdev, err);
> > +
> > +	rsdev->out_frames = out_frame;
> > +	rsdev->out_frames_cnt = cnt;
> > +
> > +out:
> > +	memset(res_frame, 0, sizeof(struct rpmb_frame));
> > +	res_frame->req_resp = req_to_resp(req);
> > +	res_frame->result = op_result(rsdev, err);
> > +	if (err != RPMB_ERR_OK) {
> > +		kfree(out_frame);
> > +		rsdev->out_frames = res_frame;
> > +		rsdev->out_frames_cnt = 1;
> > +	}
> > +
> > +	return ret;
> > +}
> > +
> > +static int rpmb_op_result_read(struct rpmb_sim_dev *rsdev,
> > +			       struct rpmb_frame *frames, u32 cnt) {
> > +	u16 req = be16_to_cpu(frames[0].req_resp);
> > +	u16 blks = be16_to_cpu(frames[0].block_count);
> > +
> > +	if (req != RPMB_RESULT_READ)
> > +		return -EINVAL;
> > +
> > +	if (blks != 0)
> > +		return -EINVAL;
> > +
> > +	rsdev->out_frames = rsdev->res_frames;
> > +	rsdev->out_frames_cnt = 1;
> > +	return 0;
> > +}
> > +
> > +static int rpmb_sim_write(struct rpmb_sim_dev *rsdev,
> > +			  struct rpmb_frame *frames, u32 cnt) {
> > +	u16 req;
> > +	int ret;
> > +
> > +	if (!frames || !cnt)
> > +		return -EINVAL;
> > +
> > +	req = be16_to_cpu(frames[0].req_resp);
> > +	if (!rsdev->auth_key_set && req != RPMB_PROGRAM_KEY)
> > +		return rpmb_op_not_programmed(rsdev, req);
> > +
> > +	switch (req) {
> > +	case RPMB_PROGRAM_KEY:
> > +		dev_dbg(rsdev->dev, "rpmb: program key\n");
> > +		ret = rpmb_op_program_key(rsdev, frames, cnt);
> > +		break;
> > +	case RPMB_WRITE_DATA:
> > +		dev_dbg(rsdev->dev, "rpmb: write data\n");
> > +		ret = rpmb_op_write_data(rsdev, frames, cnt);
> > +		break;
> > +	case RPMB_GET_WRITE_COUNTER:
> > +		dev_dbg(rsdev->dev, "rpmb: get write counter\n");
> > +		ret = rpmb_op_get_wr_counter(rsdev, frames, cnt);
> > +		break;
> > +	case RPMB_READ_DATA:
> > +		dev_dbg(rsdev->dev, "rpmb: read data\n");
> > +		ret = rpmb_op_read_data(rsdev, frames, cnt);
> > +		break;
> > +	case RPMB_RESULT_READ:
> > +		dev_dbg(rsdev->dev, "rpmb: result read\n");
> > +		ret = rpmb_op_result_read(rsdev, frames, cnt);
> > +		break;
> > +	default:
> > +		ret = -EINVAL;
> > +		break;
> > +	}
> > +
> > +	dev_dbg(rsdev->dev, "rpmb: ret=%d\n", ret);
> > +
> > +	return ret;
> > +}
> > +
> > +static int rpmb_sim_read(struct rpmb_sim_dev *rsdev,
> > +			 struct rpmb_frame *frames, u32 cnt) {
> > +	int i;
> > +
> > +	if (!frames || !cnt)
> > +		return -EINVAL;
> > +
> > +	if (!rsdev->out_frames || rsdev->out_frames_cnt == 0) {
> > +		dev_err(rsdev->dev, "out_frames are not set\n");
> > +		return -EINVAL;
> > +	}
> > +
> > +	for (i = 0; i < min_t(u32, rsdev->out_frames_cnt, cnt); i++)
> > +		memcpy(frames, rsdev->out_frames, sizeof(struct
> rpmb_frame));
> > +
> > +	if (rsdev->out_frames != rsdev->res_frames)
> > +		kfree(rsdev->out_frames);
> > +
> > +	rsdev->out_frames = NULL;
> > +	rsdev->out_frames_cnt = 0;
> > +	dev_dbg(rsdev->dev, "rpmb: cnt=%d\n", cnt);
> > +
> > +	return 0;
> > +}
> > +
> > +static int rpmb_sim_cmd_seq(struct device *dev,
> > +			    struct rpmb_cmd *cmds, u32 ncmds) {
> > +	struct platform_device *pdev;
> > +	struct rpmb_sim_dev *rsdev;
> > +	int i;
> > +	int ret;
> > +	struct rpmb_cmd *cmd;
> > +
> > +	if (!dev)
> > +		return -EINVAL;
> > +
> > +	pdev = to_platform_device(dev);
> > +	rsdev = platform_get_drvdata(pdev);
> > +
> > +	if (!rsdev)
> > +		return -EINVAL;
> > +
> > +	for (ret = 0, i = 0; i < ncmds && !ret; i++) {
> > +		cmd = &cmds[i];
> > +		if (cmd->flags & RPMB_F_WRITE)
> > +			ret = rpmb_sim_write(rsdev, cmd->frames, cmd-
> >nframes);
> > +		else
> > +			ret = rpmb_sim_read(rsdev, cmd->frames, cmd-
> >nframes);
> > +	}
> > +	return ret;
> > +}
> > +
> > +static struct rpmb_ops rpmb_sim_ops = {
> > +	.cmd_seq = rpmb_sim_cmd_seq,
> > +	.type = RPMB_TYPE_EMMC,
> > +};
> > +
> > +static int rpmb_sim_hmac_256_alloc(struct rpmb_sim_dev *rsdev) {
> > +	struct crypto_shash *hash_tfm;
> > +
> > +	hash_tfm = crypto_alloc_shash("hmac(sha256)", 0, 0);
> > +	if (IS_ERR(hash_tfm))
> > +		return PTR_ERR(hash_tfm);
> > +
> > +	rsdev->hash_tfm = hash_tfm;
> > +
> > +	dev_dbg(rsdev->dev, "hamac(sha256) registered\n");
> > +	return 0;
> > +}
> > +
> > +static void rpmb_sim_hmac_256_free(struct rpmb_sim_dev *rsdev) {
> > +	if (rsdev->hash_tfm)
> > +		crypto_free_shash(rsdev->hash_tfm);
> > +
> > +	rsdev->hash_tfm = NULL;
> > +}
> > +
> > +static int rpmb_sim_probe(struct platform_device *pdev) {
> > +	struct rpmb_sim_dev *rsdev;
> > +	int ret;
> > +
> > +	rsdev = kzalloc(sizeof(*rsdev), GFP_KERNEL);
> > +	if (!rsdev)
> > +		return -ENOMEM;
> > +
> > +	rsdev->dev = &pdev->dev;
> > +
> > +	ret = rpmb_sim_hmac_256_alloc(rsdev);
> > +	if (ret)
> > +		goto err;
> > +
> > +	rsdev->capacity = CAPACITY_UNIT * daunits;
> > +	rsdev->blkcnt  = rsdev->capacity / BLK_UNIT;
> > +	rsdev->da = kzalloc(rsdev->capacity, GFP_KERNEL);
> > +	if (!rsdev->da) {
> > +		ret = -ENOMEM;
> > +		goto err;
> > +	}
> > +
> > +	rpmb_sim_ops.dev_id_len = strlen(id);
> > +	rpmb_sim_ops.dev_id = id;
> > +	rpmb_sim_ops.reliable_wr_cnt = max_wr_blks;
> > +
> > +	rsdev->rdev = rpmb_dev_register(rsdev->dev, &rpmb_sim_ops);
> > +	if (IS_ERR(rsdev->rdev)) {
> > +		ret = PTR_ERR(rsdev->rdev);
> > +		goto err;
> > +	}
> > +
> > +	dev_info(&pdev->dev, "registered RPMB capacity = %zu of %zu
> blocks\n",
> > +		 rsdev->capacity, rsdev->blkcnt);
> > +
> > +	platform_set_drvdata(pdev, rsdev);
> > +
> > +	return 0;
> > +err:
> > +	rpmb_sim_hmac_256_free(rsdev);
> > +	if (rsdev)
> > +		kfree(rsdev->da);
> > +	kfree(rsdev);
> > +	return ret;
> > +}
> > +
> > +static int rpmb_sim_remove(struct platform_device *pdev) {
> > +	struct rpmb_sim_dev *rsdev;
> > +
> > +	rsdev = platform_get_drvdata(pdev);
> > +
> > +	rpmb_dev_unregister(rsdev->dev);
> > +
> > +	platform_set_drvdata(pdev, NULL);
> > +
> > +	rpmb_sim_hmac_256_free(rsdev);
> > +
> > +	kfree(rsdev->da);
> > +	kfree(rsdev);
> > +	return 0;
> > +}
> > +
> > +static void rpmb_sim_shutdown(struct platform_device *pdev) {
> > +	rpmb_sim_remove(pdev);
> > +}
> > +
> > +static struct platform_driver rpmb_sim_driver = {
> > +	.driver = {
> > +		.name  = "rpmb_sim",
> > +	},
> > +	.probe         = rpmb_sim_probe,
> > +	.remove        = rpmb_sim_remove,
> > +	.shutdown      = rpmb_sim_shutdown,
> > +};
> > +
> > +static struct platform_device *rpmb_sim_pdev;
> 
> A platform device?  Ick, no please don't abuse that interface for this type of
> thing.  Make it a real device if you have one, and put it in the proper place.  If
> it's a "virtual" device, great, use that.  But don't make something up like this
> please.

This is a virtual device (simulation), nothing behind it just a chunk of memory.
Is this there any information missing to make it clearer? 

Thanks
Tomas