vpd-tool: Fix for Hardware write option

With this commit, vpd-tool has a fix in Hardware (-H) write
option to update only in hardware and not in cache.

This commit also has an added change. User can provide
VPD offset(--seek) value while using read from hardware and write
to hardware options. Providing offset value(--seek) is optional.
By default offset value is 0. This option is mainly usefull
when providing an EEPROM path which is not present in VPD json.

Test: Tested on everest.

CASE 1: Using Hardware write option will update only hardware and not cache.

root@ever20bmc:/tmp# ./vpd-tool -w -H -O /sys/bus/spi/drivers/at25/spi12.0/eeprom  -R VINI -K CC --seek 0x30000 -V 0x32

root@ever20bmc:/tmp# ./vpd-tool -r -H -O /sys/bus/spi/drivers/at25/spi12.0/eeprom -R VINI -K CC --seek 0x30000
{
    "/sys/bus/spi/drivers/at25/spi12.0/eeprom": {
        "CC": "2C5F"
    }
}
root@ever20bmc:/tmp# ./vpd-tool -r -O /system/chassis/motherboard/dcm0/cpu0 -R VINI -K CC
{
    "/system/chassis/motherboard/dcm0/cpu1": {
        "CC": "5C5F"
    }
}

CASE 2: Using normal write option will update both hardware and cache

root@ever20bmc:/tmp# ./vpd-tool -w -O /system/chassis/motherboard/dcm0/cpu1 -R VINI -K CC -V 0x64

root@ever20bmc:/tmp# ./vpd-tool -r -O /system/chassis/motherboard/dcm0/cpu1  -R VINI -K CC
{
    "/system/chassis/motherboard/dcm0/cpu1": {
        "CC": "dC5F"
    }
}
root@ever20bmc:/tmp# ./vpd-tool -r -H -O /sys/bus/spi/drivers/at25/spi22.0/eeprom -R VINI -K CC --seek 0x30000

{
    "/sys/bus/spi/drivers/at25/spi22.0/eeprom": {
        "CC": "dC5F"
    }
}

CASE 3: Providing wrong offset value during hardware read

root@ever20bmc:/tmp# ./vpd-tool -r -H -O /sys/bus/i2c/drivers/at24/28-0051/eeprom -R VINI -K CC --seek 19
VHDR record not found
Did you provide a valid offset? By default VPD offset is taken as 0. To input offset, use --offset. Refer vpd-tool help.

CASE 4: Providing offset value during normal read operation. As mentioned, there'll be no impact as the offset value will be
valid only while using --Hardware/-H option.

root@ever20bmc:/tmp# ./vpd-tool -r -O /system/chassis/motherboard/dcm0/cpu1  -R VINI -K CC --seek 0
{
    "/system/chassis/motherboard/dcm0/cpu1": {
        "CC": "5C5F"
    }
}

CASE 5: Providing wrong offset value during hardware write

root@ever20bmc:/tmp# ./vpd-tool -w -H -O /sys/bus/spi/drivers/at25/spi12.0/eeprom -R VINI -K CC --seek 20 -V 0x53
Could not find start tag in VPD /sys/bus/spi/drivers/at25/spi12.0/eeprom
Did you provide a valid offset? By default VPD offset is taken as 0. To input offset, use --seek. Refer vpd-tool help.

CASE 6: Providing offset value during normal write. As mentioned, there'll be no impact as the offset value will be valid
only while using --Hardware/-H option.

root@ever8bmc:/tmp# ./vpd-tool -w -O /system/chassis/motherboard/dasd_backplane/panel1 -R VMPU -K VZ -V 0x64 --seek 19
root@ever8bmc:/tmp# ./vpd-tool -r -O /system/chassis/motherboard/dasd_backplane/panel1 -R VMPU -K VZ
{
    "/system/chassis/motherboard/dasd_backplane/panel1": {
        "VZ": "d1"
    }
}

CASE 7: Reading and Writing on a EEPROM path which is not a key in JSON.

root@ever8bmc:/tmp# ./vpd-tool -w -O /sys/bus/spi/drivers/at25/spi13.0/eeprom -R VMPU -K VZ --seek 196608 -H -V 0x64
root@ever8bmc:/tmp#
root@ever8bmc:/tmp# ./vpd-tool -r -O /sys/bus/spi/drivers/at25/spi13.0/eeprom -R VMPU -K VZ --seek 196608 -H
{
    "/sys/bus/spi/drivers/at25/spi13.0/eeprom": {
        "VZ": "d1"
    }
}

Signed-off-by: Priyanga Ramasamy <priyanga24@in.ibm.com>
Change-Id: Icc94b5ee0d044271acf7b6263405fca07eb33728
diff --git a/vpd_tool_impl.hpp b/vpd_tool_impl.hpp
index 8b1207d..3de98f9 100644
--- a/vpd_tool_impl.hpp
+++ b/vpd_tool_impl.hpp
@@ -175,20 +175,28 @@
 
     /**
      * @brief Update Hardware
-     * If the given record-keyword pair is present in dbus_properties.json,
-     * then will update the given data in both dbus and hardware.
-     * Else update the given data only in hardware.
+     * The given data is updated only on the given hardware path and not on dbus
+     * for the given record-keyword pair. The user can now update record-keyword
+     * value for any hardware path irrespective of whether its present or not in
+     * VPD JSON, by providing a valid offset. By default offset takes 0.
+     *
+     * @param[in] offset - VPD offset.
      * @return returncode (success/failure).
      */
-    int updateHardware();
+    int updateHardware(const uint32_t offset);
 
     /**
      * @brief Read Keyword from Hardware
      * This api is to read a keyword directly from the hardware. The hardware
      * path, record name and keyword name are received at the time of
      * initialising the constructor.
+     * The user can now read keyword from any hardware path irrespective of
+     * whether its present or not in VPD JSON, by providing a valid offset. By
+     * default offset takes 0.
+     *
+     * @param[in] startOffset - VPD offset.
      */
-    void readKwFromHw();
+    void readKwFromHw(const uint32_t& startOffset);
 
     /**
      * @brief Constructor