patch-2.4.6 linux/drivers/acpi/executer/exfldio.c

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diff -u --recursive --new-file v2.4.5/linux/drivers/acpi/executer/exfldio.c linux/drivers/acpi/executer/exfldio.c
@@ -0,0 +1,827 @@
+/******************************************************************************
+ *
+ * Module Name: exfldio - Aml Field I/O
+ *              $Revision: 57 $
+ *
+ *****************************************************************************/
+
+/*
+ *  Copyright (C) 2000, 2001 R. Byron Moore
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  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.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program; if not, write to the Free Software
+ *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ */
+
+
+#include "acpi.h"
+#include "acinterp.h"
+#include "amlcode.h"
+#include "acnamesp.h"
+#include "achware.h"
+#include "acevents.h"
+#include "acdispat.h"
+
+
+#define _COMPONENT          ACPI_EXECUTER
+	 MODULE_NAME         ("exfldio")
+
+
+/*******************************************************************************
+ *
+ * FUNCTION:    Acpi_ex_setup_field
+ *
+ * PARAMETERS:  *Obj_desc           - Field to be read or written
+ *              Field_datum_byte_offset  - Current offset into the field
+ *
+ * RETURN:      Status
+ *
+ * DESCRIPTION: Common processing for Acpi_ex_extract_from_field and
+ *              Acpi_ex_insert_into_field
+ *
+ ******************************************************************************/
+
+ACPI_STATUS
+acpi_ex_setup_field (
+	ACPI_OPERAND_OBJECT     *obj_desc,
+	u32                     field_datum_byte_offset)
+{
+	ACPI_STATUS             status = AE_OK;
+	ACPI_OPERAND_OBJECT     *rgn_desc;
+
+
+	/* Parameter validation */
+
+	rgn_desc = obj_desc->common_field.region_obj;
+	if (!obj_desc || !rgn_desc) {
+		return (AE_AML_NO_OPERAND);
+	}
+
+	if (ACPI_TYPE_REGION != rgn_desc->common.type) {
+		return (AE_AML_OPERAND_TYPE);
+	}
+
+
+	/*
+	 * If the Region Address and Length have not been previously evaluated,
+	 * evaluate them now and save the results.
+	 */
+	if (!(rgn_desc->region.flags & AOPOBJ_DATA_VALID)) {
+
+		status = acpi_ds_get_region_arguments (rgn_desc);
+		if (ACPI_FAILURE (status)) {
+			return (status);
+		}
+	}
+
+
+	/*
+	 * Validate the request.  The entire request from the byte offset for a
+	 * length of one field datum (access width) must fit within the region.
+	 * (Region length is specified in bytes)
+	 */
+	if (rgn_desc->region.length < (obj_desc->common_field.base_byte_offset +
+			   field_datum_byte_offset +
+			   obj_desc->common_field.access_byte_width)) {
+		if (rgn_desc->region.length < obj_desc->common_field.access_byte_width) {
+			/*
+			 * This is the case where the Access_type (Acc_word, etc.) is wider
+			 * than the region itself.  For example, a region of length one
+			 * byte, and a field with Dword access specified.
+			 */
+		}
+
+		/*
+		 * Offset rounded up to next multiple of field width
+		 * exceeds region length, indicate an error
+		 */
+		return (AE_AML_REGION_LIMIT);
+	}
+
+	return (AE_OK);
+}
+
+
+/*******************************************************************************
+ *
+ * FUNCTION:    Acpi_ex_read_field_datum
+ *
+ * PARAMETERS:  *Obj_desc           - Field to be read
+ *              *Value              - Where to store value (must be 32 bits)
+ *
+ * RETURN:      Status
+ *
+ * DESCRIPTION: Retrieve the value of the given field
+ *
+ ******************************************************************************/
+
+ACPI_STATUS
+acpi_ex_read_field_datum (
+	ACPI_OPERAND_OBJECT     *obj_desc,
+	u32                     field_datum_byte_offset,
+	u32                     *value)
+{
+	ACPI_STATUS             status;
+	ACPI_OPERAND_OBJECT     *rgn_desc;
+	ACPI_PHYSICAL_ADDRESS   address;
+	u32                     local_value;
+
+
+	if (!value) {
+		local_value = 0;
+		value = &local_value;   /*  support reads without saving value  */
+	}
+
+	/* Clear the entire return buffer first, [Very Important!] */
+
+	*value = 0;
+
+
+	/*
+	 * Buffer_fields - Read from a Buffer
+	 * Other Fields - Read from a Operation Region.
+	 */
+	switch (obj_desc->common.type) {
+	case ACPI_TYPE_BUFFER_FIELD:
+
+		/*
+		 * For Buffer_fields, we only need to copy the data from the
+		 * source buffer.  Length is the field width in bytes.
+		 */
+		MEMCPY (value, (obj_desc->buffer_field.buffer_obj)->buffer.pointer
+				  + obj_desc->buffer_field.base_byte_offset + field_datum_byte_offset,
+				  obj_desc->common_field.access_byte_width);
+		status = AE_OK;
+		break;
+
+
+	case INTERNAL_TYPE_REGION_FIELD:
+	case INTERNAL_TYPE_BANK_FIELD:
+
+		/*
+		 * For other fields, we need to go through an Operation Region
+		 * (Only types that will get here are Region_fields and Bank_fields)
+		 */
+		status = acpi_ex_setup_field (obj_desc, field_datum_byte_offset);
+		if (ACPI_FAILURE (status)) {
+			return (status);
+		}
+
+
+		/*
+		 * The physical address of this field datum is:
+		 *
+		 * 1) The base of the region, plus
+		 * 2) The base offset of the field, plus
+		 * 3) The current offset into the field
+		 */
+		rgn_desc = obj_desc->common_field.region_obj;
+		address = rgn_desc->region.address + obj_desc->common_field.base_byte_offset +
+				 field_datum_byte_offset;
+
+
+		/* Invoke the appropriate Address_space/Op_region handler */
+
+		status = acpi_ev_address_space_dispatch (rgn_desc, ACPI_READ_ADR_SPACE,
+				  address, obj_desc->common_field.access_bit_width, value);
+
+		break;
+
+
+	default:
+
+		status = AE_AML_INTERNAL;
+		break;
+	}
+
+
+	return (status);
+}
+
+
+/*******************************************************************************
+ *
+ * FUNCTION:    Acpi_ex_get_buffer_datum
+ *
+ * PARAMETERS:  Merged_datum        - Value to store
+ *              Buffer              - Receiving buffer
+ *              Byte_granularity    - 1/2/4 Granularity of the field
+ *                                    (aka Datum Size)
+ *              Offset              - Datum offset into the buffer
+ *
+ * RETURN:      none
+ *
+ * DESCRIPTION: Store the merged datum to the buffer according to the
+ *              byte granularity
+ *
+ ******************************************************************************/
+
+static void
+acpi_ex_get_buffer_datum(
+	u32                     *datum,
+	void                    *buffer,
+	u32                     byte_granularity,
+	u32                     offset)
+{
+
+	switch (byte_granularity) {
+	case ACPI_FIELD_BYTE_GRANULARITY:
+		*datum = ((u8 *) buffer) [offset];
+		break;
+
+	case ACPI_FIELD_WORD_GRANULARITY:
+		MOVE_UNALIGNED16_TO_32 (datum, &(((u16 *) buffer) [offset]));
+		break;
+
+	case ACPI_FIELD_DWORD_GRANULARITY:
+		MOVE_UNALIGNED32_TO_32 (datum, &(((u32 *) buffer) [offset]));
+		break;
+	}
+}
+
+
+/*******************************************************************************
+ *
+ * FUNCTION:    Acpi_ex_set_buffer_datum
+ *
+ * PARAMETERS:  Merged_datum        - Value to store
+ *              Buffer              - Receiving buffer
+ *              Byte_granularity    - 1/2/4 Granularity of the field
+ *                                    (aka Datum Size)
+ *              Offset              - Datum offset into the buffer
+ *
+ * RETURN:      none
+ *
+ * DESCRIPTION: Store the merged datum to the buffer according to the
+ *              byte granularity
+ *
+ ******************************************************************************/
+
+static void
+acpi_ex_set_buffer_datum (
+	u32                     merged_datum,
+	void                    *buffer,
+	u32                     byte_granularity,
+	u32                     offset)
+{
+
+	switch (byte_granularity) {
+	case ACPI_FIELD_BYTE_GRANULARITY:
+		((u8 *) buffer) [offset] = (u8) merged_datum;
+		break;
+
+	case ACPI_FIELD_WORD_GRANULARITY:
+		MOVE_UNALIGNED16_TO_16 (&(((u16 *) buffer)[offset]), &merged_datum);
+		break;
+
+	case ACPI_FIELD_DWORD_GRANULARITY:
+		MOVE_UNALIGNED32_TO_32 (&(((u32 *) buffer)[offset]), &merged_datum);
+		break;
+	}
+}
+
+
+/*******************************************************************************
+ *
+ * FUNCTION:    Acpi_ex_extract_from_field
+ *
+ * PARAMETERS:  *Obj_desc           - Field to be read
+ *              *Value              - Where to store value
+ *
+ * RETURN:      Status
+ *
+ * DESCRIPTION: Retrieve the value of the given field
+ *
+ ******************************************************************************/
+
+ACPI_STATUS
+acpi_ex_extract_from_field (
+	ACPI_OPERAND_OBJECT     *obj_desc,
+	void                    *buffer,
+	u32                     buffer_length)
+{
+	ACPI_STATUS             status;
+	u32                     field_datum_byte_offset;
+	u32                     datum_offset;
+	u32                     previous_raw_datum;
+	u32                     this_raw_datum = 0;
+	u32                     merged_datum = 0;
+	u32                     byte_field_length;
+	u32                     datum_count;
+
+
+	/*
+	 * The field must fit within the caller's buffer
+	 */
+	byte_field_length = ROUND_BITS_UP_TO_BYTES (obj_desc->common_field.bit_length);
+	if (byte_field_length > buffer_length) {
+		return (AE_BUFFER_OVERFLOW);
+	}
+
+	/* Convert field byte count to datum count, round up if necessary */
+
+	datum_count = ROUND_UP_TO (byte_field_length, obj_desc->common_field.access_byte_width);
+
+
+	/*
+	 * Clear the caller's buffer (the whole buffer length as given)
+	 * This is very important, especially in the cases where a byte is read,
+	 * but the buffer is really a u32 (4 bytes).
+	 */
+	MEMSET (buffer, 0, buffer_length);
+
+	/* Read the first raw datum to prime the loop */
+
+	field_datum_byte_offset = 0;
+	datum_offset= 0;
+
+	status = acpi_ex_read_field_datum (obj_desc, field_datum_byte_offset, &previous_raw_datum);
+	if (ACPI_FAILURE (status)) {
+		return (status);
+	}
+
+
+	/* We might actually be done if the request fits in one datum */
+
+	if ((datum_count == 1) &&
+		(obj_desc->common_field.access_flags & AFIELD_SINGLE_DATUM)) {
+		/* 1) Shift the valid data bits down to start at bit 0 */
+
+		merged_datum = (previous_raw_datum >> obj_desc->common_field.start_field_bit_offset);
+
+		/* 2) Mask off any upper unused bits (bits not part of the field) */
+
+		if (obj_desc->common_field.end_buffer_valid_bits) {
+			merged_datum &= MASK_BITS_ABOVE (obj_desc->common_field.end_buffer_valid_bits);
+		}
+
+		/* Store the datum to the caller buffer */
+
+		acpi_ex_set_buffer_datum (merged_datum, buffer, obj_desc->common_field.access_byte_width,
+				datum_offset);
+
+		return (AE_OK);
+	}
+
+
+	/* We need to get more raw data to complete one or more field data */
+
+	while (datum_offset < datum_count) {
+		field_datum_byte_offset += obj_desc->common_field.access_byte_width;
+
+		/*
+		 * If the field is aligned on a byte boundary, we don't want
+		 * to perform a final read, since this would potentially read
+		 * past the end of the region.
+		 *
+		 * TBD: [Investigate] It may make more sense to just split the aligned
+		 * and non-aligned cases since the aligned case is so very simple,
+		 */
+		if ((obj_desc->common_field.start_field_bit_offset != 0)  ||
+			((obj_desc->common_field.start_field_bit_offset == 0) &&
+			(datum_offset < (datum_count -1)))) {
+			/*
+			 * Get the next raw datum, it contains some or all bits
+			 * of the current field datum
+			 */
+			status = acpi_ex_read_field_datum (obj_desc, field_datum_byte_offset, &this_raw_datum);
+			if (ACPI_FAILURE (status)) {
+				return (status);
+			}
+		}
+
+		/*
+		 * Create the (possibly) merged datum to be stored to the caller buffer
+		 */
+		if (obj_desc->common_field.start_field_bit_offset == 0) {
+			/* Field is not skewed and we can just copy the datum */
+
+			merged_datum = previous_raw_datum;
+		}
+
+		else {
+			/*
+			 * Put together the appropriate bits of the two raw data to make a
+			 * single complete field datum
+			 *
+			 * 1) Normalize the first datum down to bit 0
+			 */
+			merged_datum = (previous_raw_datum >> obj_desc->common_field.start_field_bit_offset);
+
+			/* 2) Insert the second datum "above" the first datum */
+
+			merged_datum |= (this_raw_datum << obj_desc->common_field.datum_valid_bits);
+
+			if ((datum_offset >= (datum_count -1))) {
+				/*
+				 * This is the last iteration of the loop.  We need to clear
+				 * any unused bits (bits that are not part of this field) that
+				 * came from the last raw datum before we store the final
+				 * merged datum into the caller buffer.
+				 */
+				if (obj_desc->common_field.end_buffer_valid_bits) {
+					merged_datum &=
+						MASK_BITS_ABOVE (obj_desc->common_field.end_buffer_valid_bits);
+				}
+			}
+		}
+
+
+		/*
+		 * Store the merged field datum in the caller's buffer, according to
+		 * the granularity of the field (size of each datum).
+		 */
+		acpi_ex_set_buffer_datum (merged_datum, buffer, obj_desc->common_field.access_byte_width,
+				datum_offset);
+
+		/*
+		 * Save the raw datum that was just acquired since it may contain bits
+		 * of the *next* field datum.  Update offsets
+		 */
+		previous_raw_datum = this_raw_datum;
+		datum_offset++;
+	}
+
+
+	return (AE_OK);
+}
+
+
+/*******************************************************************************
+ *
+ * FUNCTION:    Acpi_ex_write_field_datum
+ *
+ * PARAMETERS:  *Obj_desc           - Field to be set
+ *              Value               - Value to store
+ *
+ * RETURN:      Status
+ *
+ * DESCRIPTION: Store the value into the given field
+ *
+ ******************************************************************************/
+
+static ACPI_STATUS
+acpi_ex_write_field_datum (
+	ACPI_OPERAND_OBJECT     *obj_desc,
+	u32                     field_datum_byte_offset,
+	u32                     value)
+{
+	ACPI_STATUS             status = AE_OK;
+	ACPI_OPERAND_OBJECT     *rgn_desc = NULL;
+	ACPI_PHYSICAL_ADDRESS   address;
+
+
+	/*
+	 * Buffer_fields - Read from a Buffer
+	 * Other Fields - Read from a Operation Region.
+	 */
+	switch (obj_desc->common.type) {
+	case ACPI_TYPE_BUFFER_FIELD:
+
+		/*
+		 * For Buffer_fields, we only need to copy the data to the
+		 * target buffer.  Length is the field width in bytes.
+		 */
+		MEMCPY ((obj_desc->buffer_field.buffer_obj)->buffer.pointer
+				+ obj_desc->buffer_field.base_byte_offset + field_datum_byte_offset,
+				&value, obj_desc->common_field.access_byte_width);
+		status = AE_OK;
+		break;
+
+
+	case INTERNAL_TYPE_REGION_FIELD:
+	case INTERNAL_TYPE_BANK_FIELD:
+
+		/*
+		 * For other fields, we need to go through an Operation Region
+		 * (Only types that will get here are Region_fields and Bank_fields)
+		 */
+		status = acpi_ex_setup_field (obj_desc, field_datum_byte_offset);
+		if (ACPI_FAILURE (status)) {
+			return (status);
+		}
+
+		/*
+		 * The physical address of this field datum is:
+		 *
+		 * 1) The base of the region, plus
+		 * 2) The base offset of the field, plus
+		 * 3) The current offset into the field
+		 */
+		rgn_desc = obj_desc->common_field.region_obj;
+		address = rgn_desc->region.address +
+				 obj_desc->common_field.base_byte_offset +
+				 field_datum_byte_offset;
+
+		/* Invoke the appropriate Address_space/Op_region handler */
+
+		status = acpi_ev_address_space_dispatch (rgn_desc, ACPI_WRITE_ADR_SPACE,
+				  address, obj_desc->common_field.access_bit_width, &value);
+
+
+
+		break;
+
+
+	default:
+
+		status = AE_AML_INTERNAL;
+		break;
+	}
+
+
+	return (status);
+}
+
+
+/*******************************************************************************
+ *
+ * FUNCTION:    Acpi_ex_write_field_datum_with_update_rule
+ *
+ * PARAMETERS:  *Obj_desc           - Field to be set
+ *              Value               - Value to store
+ *
+ * RETURN:      Status
+ *
+ * DESCRIPTION: Apply the field update rule to a field write
+ *
+ ******************************************************************************/
+
+static ACPI_STATUS
+acpi_ex_write_field_datum_with_update_rule (
+	ACPI_OPERAND_OBJECT     *obj_desc,
+	u32                     mask,
+	u32                     field_value,
+	u32                     field_datum_byte_offset)
+{
+	ACPI_STATUS             status = AE_OK;
+	u32                     merged_value;
+	u32                     current_value;
+
+
+	/* Start with the new bits  */
+
+	merged_value = field_value;
+
+
+	/* If the mask is all ones, we don't need to worry about the update rule */
+
+	if (mask != ACPI_UINT32_MAX) {
+		/* Decode the update rule */
+
+		switch (obj_desc->common_field.update_rule) {
+
+		case UPDATE_PRESERVE:
+
+			/*
+			 * Check if update rule needs to be applied (not if mask is all
+			 * ones)  The left shift drops the bits we want to ignore.
+			 */
+			if ((~mask << (sizeof (mask) * 8 -
+					  obj_desc->common_field.access_bit_width)) != 0) {
+				/*
+				 * Read the current contents of the byte/word/dword containing
+				 * the field, and merge with the new field value.
+				 */
+				status = acpi_ex_read_field_datum (obj_desc, field_datum_byte_offset,
+						  &current_value);
+				merged_value |= (current_value & ~mask);
+			}
+			break;
+
+
+		case UPDATE_WRITE_AS_ONES:
+
+			/* Set positions outside the field to all ones */
+
+			merged_value |= ~mask;
+			break;
+
+
+		case UPDATE_WRITE_AS_ZEROS:
+
+			/* Set positions outside the field to all zeros */
+
+			merged_value &= mask;
+			break;
+
+
+		default:
+			return (AE_AML_OPERAND_VALUE);
+			break;
+		}
+	}
+
+
+	/* Write the merged value */
+
+	status = acpi_ex_write_field_datum (obj_desc, field_datum_byte_offset,
+			  merged_value);
+
+	return (status);
+}
+
+
+/*******************************************************************************
+ *
+ * FUNCTION:    Acpi_ex_insert_into_field
+ *
+ * PARAMETERS:  *Obj_desc           - Field to be set
+ *              Buffer              - Value to store
+ *
+ * RETURN:      Status
+ *
+ * DESCRIPTION: Store the value into the given field
+ *
+ ******************************************************************************/
+
+ACPI_STATUS
+acpi_ex_insert_into_field (
+	ACPI_OPERAND_OBJECT     *obj_desc,
+	void                    *buffer,
+	u32                     buffer_length)
+{
+	ACPI_STATUS             status;
+	u32                     field_datum_byte_offset;
+	u32                     datum_offset;
+	u32                     mask;
+	u32                     merged_datum;
+	u32                     previous_raw_datum;
+	u32                     this_raw_datum;
+	u32                     byte_field_length;
+	u32                     datum_count;
+
+
+	/*
+	 * Incoming buffer must be at least as long as the field, we do not
+	 * allow "partial" field writes.  We do not care if the buffer is
+	 * larger than the field, this typically happens when an integer is
+	 * written to a field that is actually smaller than an integer.
+	 */
+	byte_field_length = ROUND_BITS_UP_TO_BYTES (obj_desc->common_field.bit_length);
+	if (buffer_length < byte_field_length) {
+		/* TBD: Need a better error code */
+
+		return (AE_BUFFER_OVERFLOW);
+	}
+
+	/* Convert byte count to datum count, round up if necessary */
+
+	datum_count = ROUND_UP_TO (byte_field_length, obj_desc->common_field.access_byte_width);
+
+
+	/*
+	 * Break the request into up to three parts (similar to an I/O request):
+	 * 1) non-aligned part at start
+	 * 2) aligned part in middle
+	 * 3) non-aligned part at the end
+	 */
+	field_datum_byte_offset = 0;
+	datum_offset= 0;
+
+	/* Get a single datum from the caller's buffer */
+
+	acpi_ex_get_buffer_datum (&previous_raw_datum, buffer,
+			obj_desc->common_field.access_byte_width, datum_offset);
+
+	/*
+	 * Part1:
+	 * Write a partial field datum if field does not begin on a datum boundary
+	 * Note: The code in this section also handles the aligned case
+	 *
+	 * Construct Mask with 1 bits where the field is, 0 bits elsewhere
+	 * (Only the bottom 5 bits of Bit_length are valid for a shift operation)
+	 *
+	 * Mask off bits that are "below" the field (if any)
+	 */
+	mask = MASK_BITS_BELOW (obj_desc->common_field.start_field_bit_offset);
+
+	/* If the field fits in one datum, may need to mask upper bits */
+
+	if ((obj_desc->common_field.access_flags & AFIELD_SINGLE_DATUM) &&
+		 obj_desc->common_field.end_field_valid_bits) {
+		/* There are bits above the field, mask them off also */
+
+		mask &= MASK_BITS_ABOVE (obj_desc->common_field.end_field_valid_bits);
+	}
+
+	/* Shift and mask the value into the field position */
+
+	merged_datum = (previous_raw_datum << obj_desc->common_field.start_field_bit_offset);
+	merged_datum &= mask;
+
+	/* Apply the update rule (if necessary) and write the datum to the field */
+
+	status = acpi_ex_write_field_datum_with_update_rule (obj_desc, mask, merged_datum,
+			   field_datum_byte_offset);
+	if (ACPI_FAILURE (status)) {
+		return (status);
+	}
+
+	/* If the entire field fits within one datum, we are done. */
+
+	if ((datum_count == 1) &&
+	   (obj_desc->common_field.access_flags & AFIELD_SINGLE_DATUM)) {
+		return (AE_OK);
+	}
+
+	/*
+	 * Part2:
+	 * Write the aligned data.
+	 *
+	 * We don't need to worry about the update rule for these data, because
+	 * all of the bits in each datum are part of the field.
+	 *
+	 * The last datum must be special cased because it might contain bits
+	 * that are not part of the field -- therefore the "update rule" must be
+	 * applied in Part3 below.
+	 */
+	while (datum_offset < datum_count) {
+		datum_offset++;
+		field_datum_byte_offset += obj_desc->common_field.access_byte_width;
+
+		/*
+		 * Get the next raw buffer datum.  It may contain bits of the previous
+		 * field datum
+		 */
+		acpi_ex_get_buffer_datum (&this_raw_datum, buffer,
+				obj_desc->common_field.access_byte_width, datum_offset);
+
+		/* Create the field datum based on the field alignment */
+
+		if (obj_desc->common_field.start_field_bit_offset != 0) {
+			/*
+			 * Put together appropriate bits of the two raw buffer data to make
+			 * a single complete field datum
+			 */
+			merged_datum =
+				(previous_raw_datum >> obj_desc->common_field.datum_valid_bits) |
+				(this_raw_datum << obj_desc->common_field.start_field_bit_offset);
+		}
+
+		else {
+			/* Field began aligned on datum boundary */
+
+			merged_datum = this_raw_datum;
+		}
+
+
+		/*
+		 * Special handling for the last datum if the field does NOT end on
+		 * a datum boundary.  Update Rule must be applied to the bits outside
+		 * the field.
+		 */
+		if ((datum_offset == datum_count)           &&
+			obj_desc->common_field.end_field_valid_bits) {
+			/*
+			 * Part3:
+			 * This is the last datum and the field does not end on a datum boundary.
+			 * Build the partial datum and write with the update rule.
+			 */
+
+			/* Mask off the unused bits above (after) the end-of-field */
+
+			mask = MASK_BITS_ABOVE (obj_desc->common_field.end_field_valid_bits);
+			merged_datum &= mask;
+
+			/* Write the last datum with the update rule */
+
+			status = acpi_ex_write_field_datum_with_update_rule (obj_desc, mask,
+					  merged_datum, field_datum_byte_offset);
+			if (ACPI_FAILURE (status)) {
+				return (status);
+			}
+		}
+
+		else {
+			/* Normal case -- write the completed datum */
+
+			status = acpi_ex_write_field_datum (obj_desc,
+					  field_datum_byte_offset, merged_datum);
+			if (ACPI_FAILURE (status)) {
+				return (status);
+			}
+		}
+
+		/*
+		 * Save the most recent datum since it may contain bits of the *next*
+		 * field datum.  Update current byte offset.
+		 */
+		previous_raw_datum = this_raw_datum;
+	}
+
+
+	return (status);
+}
+
+

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TCL-scripts by Sam Shen (who was at: slshen@lbl.gov)