ACPI: consolidate functions in acpi ec driver

Unify the following functions:

    acpi_ec_poll_read()
    acpi_ec_poll_write()
    acpi_ec_poll_query()
    acpi_ec_intr_read()
    acpi_ec_intr_write()
    acpi_ec_intr_query()

into:

    acpi_ec_poll_transaction()
    acpi_ec_intr_transaction()

These new functions take as arguments an ACPI EC command, a few bytes
to write to the EC data register and a buffer for a few bytes to read
from the EC data register. The old _read(), _write(), _query() are
just special cases of these functions.

Then unified the code in acpi_ec_poll_transaction() and
acpi_ec_intr_transaction() a little more. Both functions are now just
wrappers around the new acpi_ec_transaction_unlocked() function. The
latter contains the EC access logic, the two original
function now just do their special way of locking and call the the
new function for the actual work.

This saves a lot of very similar code. The primary reason for doing
this, however, is that my driver for MSI 270 laptops needs to issue
some non-standard EC commands in a safe way. Due to this I added a new
exported function similar to ec_write()/ec_write() which is called
ec_transaction() and is essentially just a wrapper around
acpi_ec_{poll,intr}_transaction().
Signed-off-by: Lennart Poettering <mzxreary@0pointer.de>
Acked-by: Luming Yu <luming.yu@intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Len Brown <len.brown@intel.com>

include/linux/acpi.h

@@ -494,6 +494,9 @@ void acpi_pci_unregister_driver(struct acpi_pci_driver *driver);
 
 extern int ec_read(u8 addr, u8 *val);
 extern int ec_write(u8 addr, u8 val);
+extern int ec_transaction(u8 command,
+                          const u8 *wdata, unsigned wdata_len,
+                          u8 *rdata, unsigned rdata_len);
 
 #endif /*CONFIG_ACPI_EC*/