drivers/slimbus/messaging.c - third_party/linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0
 /*
  * Copyright (c) 2011-2017, The Linux Foundation
  */

 #include <linux/slab.h>
 #include <linux/pm_runtime.h>
 #include "slimbus.h"

 /**
  * slim_msg_response() - Deliver Message response received from a device to the
  *			framework.
  *
  * @ctrl: Controller handle
  * @reply: Reply received from the device
  * @len: Length of the reply
  * @tid: Transaction ID received with which framework can associate reply.
  *
  * Called by controller to inform framework about the response received.
  * This helps in making the API asynchronous, and controller-driver doesn't need
  * to manage 1 more table other than the one managed by framework mapping TID
  * with buffers
  */
 void slim_msg_response(struct slim_controller *ctrl, u8 *reply, u8 tid, u8 len)
 {
 	struct slim_msg_txn *txn;
 	struct slim_val_inf *msg;
 	unsigned long flags;

 	spin_lock_irqsave(&ctrl->txn_lock, flags);
 	txn = idr_find(&ctrl->tid_idr, tid);
 	spin_unlock_irqrestore(&ctrl->txn_lock, flags);

 	if (txn == NULL)
 		return;

 	msg = txn->msg;
 	if (msg == NULL || msg->rbuf == NULL) {
 		dev_err(ctrl->dev, "Got response to invalid TID:%d, len:%d\n",
 				tid, len);
 		return;
 	}

 	slim_free_txn_tid(ctrl, txn);
 	memcpy(msg->rbuf, reply, len);
 	if (txn->comp)
 		complete(txn->comp);

 	/* Remove runtime-pm vote now that response was received for TID txn */
 	pm_runtime_mark_last_busy(ctrl->dev);
 	pm_runtime_put_autosuspend(ctrl->dev);
 }
 EXPORT_SYMBOL_GPL(slim_msg_response);

 /**
  * slim_alloc_txn_tid() - Allocate a tid to txn
  *
  * @ctrl: Controller handle
  * @txn: transaction to be allocated with tid.
  *
  * Return: zero on success with valid txn->tid and error code on failures.
  */
 int slim_alloc_txn_tid(struct slim_controller *ctrl, struct slim_msg_txn *txn)
 {
 	unsigned long flags;
 	int ret = 0;

 	spin_lock_irqsave(&ctrl->txn_lock, flags);
 	ret = idr_alloc_cyclic(&ctrl->tid_idr, txn, 1,
 				SLIM_MAX_TIDS, GFP_ATOMIC);
 	if (ret < 0) {
 		spin_unlock_irqrestore(&ctrl->txn_lock, flags);
 		return ret;
 	}
 	txn->tid = ret;
 	spin_unlock_irqrestore(&ctrl->txn_lock, flags);
 	return 0;
 }
 EXPORT_SYMBOL_GPL(slim_alloc_txn_tid);

 /**
  * slim_free_txn_tid() - Freee tid of txn
  *
  * @ctrl: Controller handle
  * @txn: transaction whose tid should be freed
  */
 void slim_free_txn_tid(struct slim_controller *ctrl, struct slim_msg_txn *txn)
 {
 	unsigned long flags;

 	spin_lock_irqsave(&ctrl->txn_lock, flags);
 	idr_remove(&ctrl->tid_idr, txn->tid);
 	spin_unlock_irqrestore(&ctrl->txn_lock, flags);
 }
 EXPORT_SYMBOL_GPL(slim_free_txn_tid);

 /**
  * slim_do_transfer() - Process a SLIMbus-messaging transaction
  *
  * @ctrl: Controller handle
  * @txn: Transaction to be sent over SLIMbus
  *
  * Called by controller to transmit messaging transactions not dealing with
  * Interface/Value elements. (e.g. transmittting a message to assign logical
  * address to a slave device
  *
  * Return: -ETIMEDOUT: If transmission of this message timed out
  *	(e.g. due to bus lines not being clocked or driven by controller)
  */
 int slim_do_transfer(struct slim_controller *ctrl, struct slim_msg_txn *txn)
 {
 	DECLARE_COMPLETION_ONSTACK(done);
 	bool need_tid = false, clk_pause_msg = false;
 	int ret, timeout;

 	/*
 	 * do not vote for runtime-PM if the transactions are part of clock
 	 * pause sequence
 	 */
 	if (ctrl->sched.clk_state == SLIM_CLK_ENTERING_PAUSE &&
 		(txn->mt == SLIM_MSG_MT_CORE &&
 		 txn->mc >= SLIM_MSG_MC_BEGIN_RECONFIGURATION &&
 		 txn->mc <= SLIM_MSG_MC_RECONFIGURE_NOW))
 		clk_pause_msg = true;

 	if (!clk_pause_msg) {
 		ret = pm_runtime_get_sync(ctrl->dev);
 		if (ctrl->sched.clk_state != SLIM_CLK_ACTIVE) {
 			dev_err(ctrl->dev, "ctrl wrong state:%d, ret:%d\n",
 				ctrl->sched.clk_state, ret);
 			goto slim_xfer_err;
 		}
 	}
 	/* Initialize tid to invalid value */
 	txn->tid = 0;
 	need_tid = slim_tid_txn(txn->mt, txn->mc);

 	if (need_tid) {
 		ret = slim_alloc_txn_tid(ctrl, txn);
 		if (ret)
 			return ret;

 		if (!txn->msg->comp)
 			txn->comp = &done;
 		else
 			txn->comp = txn->comp;
 	}

 	ret = ctrl->xfer_msg(ctrl, txn);

 	if (!ret && need_tid && !txn->msg->comp) {
 		unsigned long ms = txn->rl + HZ;

 		timeout = wait_for_completion_timeout(txn->comp,
 						      msecs_to_jiffies(ms));
 		if (!timeout) {
 			ret = -ETIMEDOUT;
 			slim_free_txn_tid(ctrl, txn);
 		}
 	}

 	if (ret)
 		dev_err(ctrl->dev, "Tx:MT:0x%x, MC:0x%x, LA:0x%x failed:%d\n",
 			txn->mt, txn->mc, txn->la, ret);

 slim_xfer_err:
 	if (!clk_pause_msg && (txn->tid == 0  || ret == -ETIMEDOUT)) {
 		/*
 		 * remove runtime-pm vote if this was TX only, or
 		 * if there was error during this transaction
 		 */
 		pm_runtime_mark_last_busy(ctrl->dev);
 		pm_runtime_put_autosuspend(ctrl->dev);
 	}
 	return ret;
 }
 EXPORT_SYMBOL_GPL(slim_do_transfer);

 static int slim_val_inf_sanity(struct slim_controller *ctrl,
 			       struct slim_val_inf *msg, u8 mc)
 {
 	if (!msg || msg->num_bytes > 16 ||
 	    (msg->start_offset + msg->num_bytes) > 0xC00)
 		goto reterr;
 	switch (mc) {
 	case SLIM_MSG_MC_REQUEST_VALUE:
 	case SLIM_MSG_MC_REQUEST_INFORMATION:
 		if (msg->rbuf != NULL)
 			return 0;
 		break;

 	case SLIM_MSG_MC_CHANGE_VALUE:
 	case SLIM_MSG_MC_CLEAR_INFORMATION:
 		if (msg->wbuf != NULL)
 			return 0;
 		break;

 	case SLIM_MSG_MC_REQUEST_CHANGE_VALUE:
 	case SLIM_MSG_MC_REQUEST_CLEAR_INFORMATION:
 		if (msg->rbuf != NULL && msg->wbuf != NULL)
 			return 0;
 		break;
 	}
 reterr:
 	if (msg)
 		dev_err(ctrl->dev, "Sanity check failed:msg:offset:0x%x, mc:%d\n",
 			msg->start_offset, mc);
 	return -EINVAL;
 }

 static u16 slim_slicesize(int code)
 {
 	static const u8 sizetocode[16] = {
 		0, 1, 2, 3, 3, 4, 4, 5, 5, 5, 5, 6, 6, 6, 6, 7
 	};

 	code = clamp(code, 1, (int)ARRAY_SIZE(sizetocode));

 	return sizetocode[code - 1];
 }

 /**
  * slim_xfer_msg() - Transfer a value info message on slim device
  *
  * @sbdev: slim device to which this msg has to be transfered
  * @msg: value info message pointer
  * @mc: message code of the message
  *
  * Called by drivers which want to transfer a vlaue or info elements.
  *
  * Return: -ETIMEDOUT: If transmission of this message timed out
  */
 int slim_xfer_msg(struct slim_device *sbdev, struct slim_val_inf *msg,
 		  u8 mc)
 {
 	DEFINE_SLIM_LDEST_TXN(txn_stack, mc, 6, sbdev->laddr, msg);
 	struct slim_msg_txn *txn = &txn_stack;
 	struct slim_controller *ctrl = sbdev->ctrl;
 	int ret;
 	u16 sl;

 	if (!ctrl)
 		return -EINVAL;

 	ret = slim_val_inf_sanity(ctrl, msg, mc);
 	if (ret)
 		return ret;

 	sl = slim_slicesize(msg->num_bytes);

 	dev_dbg(ctrl->dev, "SB xfer msg:os:%x, len:%d, MC:%x, sl:%x\n",
 		msg->start_offset, msg->num_bytes, mc, sl);

 	txn->ec = ((sl | (1 << 3)) | ((msg->start_offset & 0xFFF) << 4));

 	switch (mc) {
 	case SLIM_MSG_MC_REQUEST_CHANGE_VALUE:
 	case SLIM_MSG_MC_CHANGE_VALUE:
 	case SLIM_MSG_MC_REQUEST_CLEAR_INFORMATION:
 	case SLIM_MSG_MC_CLEAR_INFORMATION:
 		txn->rl += msg->num_bytes;
 	default:
 		break;
 	}

 	if (slim_tid_txn(txn->mt, txn->mc))
 		txn->rl++;

 	return slim_do_transfer(ctrl, txn);
 }
 EXPORT_SYMBOL_GPL(slim_xfer_msg);

 static void slim_fill_msg(struct slim_val_inf *msg, u32 addr,
 			 size_t count, u8 *rbuf, u8 *wbuf)
 {
 	msg->start_offset = addr;
 	msg->num_bytes = count;
 	msg->rbuf = rbuf;
 	msg->wbuf = wbuf;
 	msg->comp = NULL;
 }

 /**
  * slim_read() - Read SLIMbus value element
  *
  * @sdev: client handle.
  * @addr:  address of value element to read.
  * @count: number of bytes to read. Maximum bytes allowed are 16.
  * @val: will return what the value element value was
  *
  * Return: -EINVAL for Invalid parameters, -ETIMEDOUT If transmission of
  * this message timed out (e.g. due to bus lines not being clocked
  * or driven by controller)
  */
 int slim_read(struct slim_device *sdev, u32 addr, size_t count, u8 *val)
 {
 	struct slim_val_inf msg;

 	slim_fill_msg(&msg, addr, count, val, NULL);

 	return slim_xfer_msg(sdev, &msg, SLIM_MSG_MC_REQUEST_VALUE);
 }
 EXPORT_SYMBOL_GPL(slim_read);

 /**
  * slim_readb() - Read byte from SLIMbus value element
  *
  * @sdev: client handle.
  * @addr:  address in the value element to read.
  *
  * Return: byte value of value element.
  */
 int slim_readb(struct slim_device *sdev, u32 addr)
 {
 	int ret;
 	u8 buf;

 	ret = slim_read(sdev, addr, 1, &buf);
 	if (ret < 0)
 		return ret;
 	else
 		return buf;
 }
 EXPORT_SYMBOL_GPL(slim_readb);

 /**
  * slim_write() - Write SLIMbus value element
  *
  * @sdev: client handle.
  * @addr:  address in the value element to write.
  * @count: number of bytes to write. Maximum bytes allowed are 16.
  * @val: value to write to value element
  *
  * Return: -EINVAL for Invalid parameters, -ETIMEDOUT If transmission of
  * this message timed out (e.g. due to bus lines not being clocked
  * or driven by controller)
  */
 int slim_write(struct slim_device *sdev, u32 addr, size_t count, u8 *val)
 {
 	struct slim_val_inf msg;

 	slim_fill_msg(&msg, addr, count,  NULL, val);

 	return slim_xfer_msg(sdev, &msg, SLIM_MSG_MC_CHANGE_VALUE);
 }
 EXPORT_SYMBOL_GPL(slim_write);

 /**
  * slim_writeb() - Write byte to SLIMbus value element
  *
  * @sdev: client handle.
  * @addr:  address of value element to write.
  * @value: value to write to value element
  *
  * Return: -EINVAL for Invalid parameters, -ETIMEDOUT If transmission of
  * this message timed out (e.g. due to bus lines not being clocked
  * or driven by controller)
  *
  */
 int slim_writeb(struct slim_device *sdev, u32 addr, u8 value)
 {
 	return slim_write(sdev, addr, 1, &value);
 }
 EXPORT_SYMBOL_GPL(slim_writeb);
	// SPDX-License-Identifier: GPL-2.0
	/*
	* Copyright (c) 2011-2017, The Linux Foundation
	*/

	#include <linux/slab.h>
	#include <linux/pm_runtime.h>
	#include "slimbus.h"

	/**
	* slim_msg_response() - Deliver Message response received from a device to the
	* framework.
	*
	* @ctrl: Controller handle
	* @reply: Reply received from the device
	* @len: Length of the reply
	* @tid: Transaction ID received with which framework can associate reply.
	*
	* Called by controller to inform framework about the response received.
	* This helps in making the API asynchronous, and controller-driver doesn't need
	* to manage 1 more table other than the one managed by framework mapping TID
	* with buffers
	*/
	void slim_msg_response(struct slim_controller ctrl, u8 reply, u8 tid, u8 len)
	{
	struct slim_msg_txn *txn;
	struct slim_val_inf *msg;
	unsigned long flags;

	spin_lock_irqsave(&ctrl->txn_lock, flags);
	txn = idr_find(&ctrl->tid_idr, tid);
	spin_unlock_irqrestore(&ctrl->txn_lock, flags);

	if (txn == NULL)
	return;

	msg = txn->msg;
	if (msg == NULL \|\| msg->rbuf == NULL) {
	dev_err(ctrl->dev, "Got response to invalid TID:%d, len:%d\n",
	tid, len);
	return;
	}

	slim_free_txn_tid(ctrl, txn);
	memcpy(msg->rbuf, reply, len);
	if (txn->comp)
	complete(txn->comp);

	/* Remove runtime-pm vote now that response was received for TID txn */
	pm_runtime_mark_last_busy(ctrl->dev);
	pm_runtime_put_autosuspend(ctrl->dev);
	}
	EXPORT_SYMBOL_GPL(slim_msg_response);

	/**
	* slim_alloc_txn_tid() - Allocate a tid to txn
	*
	* @ctrl: Controller handle
	* @txn: transaction to be allocated with tid.
	*
	* Return: zero on success with valid txn->tid and error code on failures.
	*/
	int slim_alloc_txn_tid(struct slim_controller ctrl, struct slim_msg_txn txn)
	{
	unsigned long flags;
	int ret = 0;

	spin_lock_irqsave(&ctrl->txn_lock, flags);
	ret = idr_alloc_cyclic(&ctrl->tid_idr, txn, 1,
	SLIM_MAX_TIDS, GFP_ATOMIC);
	if (ret < 0) {
	spin_unlock_irqrestore(&ctrl->txn_lock, flags);
	return ret;
	}
	txn->tid = ret;
	spin_unlock_irqrestore(&ctrl->txn_lock, flags);
	return 0;
	}
	EXPORT_SYMBOL_GPL(slim_alloc_txn_tid);

	/**
	* slim_free_txn_tid() - Freee tid of txn
	*
	* @ctrl: Controller handle
	* @txn: transaction whose tid should be freed
	*/
	void slim_free_txn_tid(struct slim_controller ctrl, struct slim_msg_txn txn)
	{
	unsigned long flags;

	spin_lock_irqsave(&ctrl->txn_lock, flags);
	idr_remove(&ctrl->tid_idr, txn->tid);
	spin_unlock_irqrestore(&ctrl->txn_lock, flags);
	}
	EXPORT_SYMBOL_GPL(slim_free_txn_tid);

	/**
	* slim_do_transfer() - Process a SLIMbus-messaging transaction
	*
	* @ctrl: Controller handle
	* @txn: Transaction to be sent over SLIMbus
	*
	* Called by controller to transmit messaging transactions not dealing with
	* Interface/Value elements. (e.g. transmittting a message to assign logical
	* address to a slave device
	*
	* Return: -ETIMEDOUT: If transmission of this message timed out
	* (e.g. due to bus lines not being clocked or driven by controller)
	*/
	int slim_do_transfer(struct slim_controller ctrl, struct slim_msg_txn txn)
	{
	DECLARE_COMPLETION_ONSTACK(done);
	bool need_tid = false, clk_pause_msg = false;
	int ret, timeout;

	/*
	* do not vote for runtime-PM if the transactions are part of clock
	* pause sequence
	*/
	if (ctrl->sched.clk_state == SLIM_CLK_ENTERING_PAUSE &&
	(txn->mt == SLIM_MSG_MT_CORE &&
	txn->mc >= SLIM_MSG_MC_BEGIN_RECONFIGURATION &&
	txn->mc <= SLIM_MSG_MC_RECONFIGURE_NOW))
	clk_pause_msg = true;

	if (!clk_pause_msg) {
	ret = pm_runtime_get_sync(ctrl->dev);
	if (ctrl->sched.clk_state != SLIM_CLK_ACTIVE) {
	dev_err(ctrl->dev, "ctrl wrong state:%d, ret:%d\n",
	ctrl->sched.clk_state, ret);
	goto slim_xfer_err;
	}
	}
	/* Initialize tid to invalid value */
	txn->tid = 0;
	need_tid = slim_tid_txn(txn->mt, txn->mc);

	if (need_tid) {
	ret = slim_alloc_txn_tid(ctrl, txn);
	if (ret)
	return ret;

	if (!txn->msg->comp)
	txn->comp = &done;
	else
	txn->comp = txn->comp;
	}

	ret = ctrl->xfer_msg(ctrl, txn);

	if (!ret && need_tid && !txn->msg->comp) {
	unsigned long ms = txn->rl + HZ;

	timeout = wait_for_completion_timeout(txn->comp,
	msecs_to_jiffies(ms));
	if (!timeout) {
	ret = -ETIMEDOUT;
	slim_free_txn_tid(ctrl, txn);
	}
	}

	if (ret)
	dev_err(ctrl->dev, "Tx:MT:0x%x, MC:0x%x, LA:0x%x failed:%d\n",
	txn->mt, txn->mc, txn->la, ret);

	slim_xfer_err:
	if (!clk_pause_msg && (txn->tid == 0 \|\| ret == -ETIMEDOUT)) {
	/*
	* remove runtime-pm vote if this was TX only, or
	* if there was error during this transaction
	*/
	pm_runtime_mark_last_busy(ctrl->dev);
	pm_runtime_put_autosuspend(ctrl->dev);
	}
	return ret;
	}
	EXPORT_SYMBOL_GPL(slim_do_transfer);

	static int slim_val_inf_sanity(struct slim_controller *ctrl,
	struct slim_val_inf *msg, u8 mc)
	{
	if (!msg \|\| msg->num_bytes > 16 \|\|
	(msg->start_offset + msg->num_bytes) > 0xC00)
	goto reterr;
	switch (mc) {
	case SLIM_MSG_MC_REQUEST_VALUE:
	case SLIM_MSG_MC_REQUEST_INFORMATION:
	if (msg->rbuf != NULL)
	return 0;
	break;

	case SLIM_MSG_MC_CHANGE_VALUE:
	case SLIM_MSG_MC_CLEAR_INFORMATION:
	if (msg->wbuf != NULL)
	return 0;
	break;

	case SLIM_MSG_MC_REQUEST_CHANGE_VALUE:
	case SLIM_MSG_MC_REQUEST_CLEAR_INFORMATION:
	if (msg->rbuf != NULL && msg->wbuf != NULL)
	return 0;
	break;
	}
	reterr:
	if (msg)
	dev_err(ctrl->dev, "Sanity check failed:msg:offset:0x%x, mc:%d\n",
	msg->start_offset, mc);
	return -EINVAL;
	}

	static u16 slim_slicesize(int code)
	{
	static const u8 sizetocode[16] = {
	0, 1, 2, 3, 3, 4, 4, 5, 5, 5, 5, 6, 6, 6, 6, 7
	};

	code = clamp(code, 1, (int)ARRAY_SIZE(sizetocode));

	return sizetocode[code - 1];
	}

	/**
	* slim_xfer_msg() - Transfer a value info message on slim device
	*
	* @sbdev: slim device to which this msg has to be transfered
	* @msg: value info message pointer
	* @mc: message code of the message
	*
	* Called by drivers which want to transfer a vlaue or info elements.
	*
	* Return: -ETIMEDOUT: If transmission of this message timed out
	*/
	int slim_xfer_msg(struct slim_device sbdev, struct slim_val_inf msg,
	u8 mc)
	{
	DEFINE_SLIM_LDEST_TXN(txn_stack, mc, 6, sbdev->laddr, msg);
	struct slim_msg_txn *txn = &txn_stack;
	struct slim_controller *ctrl = sbdev->ctrl;
	int ret;
	u16 sl;

	if (!ctrl)
	return -EINVAL;

	ret = slim_val_inf_sanity(ctrl, msg, mc);
	if (ret)
	return ret;

	sl = slim_slicesize(msg->num_bytes);

	dev_dbg(ctrl->dev, "SB xfer msg:os:%x, len:%d, MC:%x, sl:%x\n",
	msg->start_offset, msg->num_bytes, mc, sl);

	txn->ec = ((sl \| (1 << 3)) \| ((msg->start_offset & 0xFFF) << 4));

	switch (mc) {
	case SLIM_MSG_MC_REQUEST_CHANGE_VALUE:
	case SLIM_MSG_MC_CHANGE_VALUE:
	case SLIM_MSG_MC_REQUEST_CLEAR_INFORMATION:
	case SLIM_MSG_MC_CLEAR_INFORMATION:
	txn->rl += msg->num_bytes;
	default:
	break;
	}

	if (slim_tid_txn(txn->mt, txn->mc))
	txn->rl++;

	return slim_do_transfer(ctrl, txn);
	}
	EXPORT_SYMBOL_GPL(slim_xfer_msg);

	static void slim_fill_msg(struct slim_val_inf *msg, u32 addr,
	size_t count, u8 rbuf, u8 wbuf)
	{
	msg->start_offset = addr;
	msg->num_bytes = count;
	msg->rbuf = rbuf;
	msg->wbuf = wbuf;
	msg->comp = NULL;
	}

	/**
	* slim_read() - Read SLIMbus value element
	*
	* @sdev: client handle.
	* @addr: address of value element to read.
	* @count: number of bytes to read. Maximum bytes allowed are 16.
	* @val: will return what the value element value was
	*
	* Return: -EINVAL for Invalid parameters, -ETIMEDOUT If transmission of
	* this message timed out (e.g. due to bus lines not being clocked
	* or driven by controller)
	*/
	int slim_read(struct slim_device sdev, u32 addr, size_t count, u8 val)
	{
	struct slim_val_inf msg;

	slim_fill_msg(&msg, addr, count, val, NULL);

	return slim_xfer_msg(sdev, &msg, SLIM_MSG_MC_REQUEST_VALUE);
	}
	EXPORT_SYMBOL_GPL(slim_read);

	/**
	* slim_readb() - Read byte from SLIMbus value element
	*
	* @sdev: client handle.
	* @addr: address in the value element to read.
	*
	* Return: byte value of value element.
	*/
	int slim_readb(struct slim_device *sdev, u32 addr)
	{
	int ret;
	u8 buf;

	ret = slim_read(sdev, addr, 1, &buf);
	if (ret < 0)
	return ret;
	else
	return buf;
	}
	EXPORT_SYMBOL_GPL(slim_readb);

	/**
	* slim_write() - Write SLIMbus value element
	*
	* @sdev: client handle.
	* @addr: address in the value element to write.
	* @count: number of bytes to write. Maximum bytes allowed are 16.
	* @val: value to write to value element
	*
	* Return: -EINVAL for Invalid parameters, -ETIMEDOUT If transmission of
	* this message timed out (e.g. due to bus lines not being clocked
	* or driven by controller)
	*/
	int slim_write(struct slim_device sdev, u32 addr, size_t count, u8 val)
	{
	struct slim_val_inf msg;

	slim_fill_msg(&msg, addr, count, NULL, val);

	return slim_xfer_msg(sdev, &msg, SLIM_MSG_MC_CHANGE_VALUE);
	}
	EXPORT_SYMBOL_GPL(slim_write);

	/**
	* slim_writeb() - Write byte to SLIMbus value element
	*
	* @sdev: client handle.
	* @addr: address of value element to write.
	* @value: value to write to value element
	*
	* Return: -EINVAL for Invalid parameters, -ETIMEDOUT If transmission of
	* this message timed out (e.g. due to bus lines not being clocked
	* or driven by controller)
	*
	*/
	int slim_writeb(struct slim_device *sdev, u32 addr, u8 value)
	{
	return slim_write(sdev, addr, 1, &value);
	}
	EXPORT_SYMBOL_GPL(slim_writeb);