platform/chrome: cros_ec_lpc: Handle zero length read/write

cros_ec_lpc_mec_read_bytes and cros_ec_lpc_mec_write_bytes call
cros_ec_lpc_mec_in_range, which checks if addresses are in the MEC
address range, and returns -EINVAL if the range given is not sensible.

However cros_ec_lpc_mec_in_range was also returning -EINVAL for a zero
length range.

A zero length range should not be an error condition.
cros_ec_lpc_mec_in_range now returns 1 in this case.
cros_ec_lpc_io_bytes_mec checks for zero length, and returns
immediately without beginning a transfer.

Fixes: 68dbac0a58ef ("platform/chrome: cros_ec_lpc: MEC access can return error code")
Fixes: 77a714325d09 ("platform/chrome: cros_ec_lpc: Fix error code in cros_ec_lpc_mec_read_bytes()")
Signed-off-by: Ben Walsh <ben@jubnut.com>
Link: https://lore.kernel.org/r/20240613212542.403-1-ben@jubnut.com
Signed-off-by: Tzung-Bi Shih <tzungbi@kernel.org>

diff --git a/drivers/platform/chrome/cros_ec_lpc_mec.c b/drivers/platform/chrome/cros_ec_lpc_mec.c
index dfad934e65ca60985a2349485cc6f01445a0e047..a56584171168c352497c695dde7f6316f8de8a80 100644 (file)
--- a/drivers/platform/chrome/cros_ec_lpc_mec.c
+++ b/drivers/platform/chrome/cros_ec_lpc_mec.c
@@ -93,9 +93,6 @@ static void cros_ec_lpc_mec_emi_write_address(u16 addr,
  */
 int cros_ec_lpc_mec_in_range(unsigned int offset, unsigned int length)
 {
-       if (length == 0)
-               return -EINVAL;
-
        if (WARN_ON(mec_emi_base == 0 || mec_emi_end == 0))
                return -EINVAL;
 
@@ -132,6 +129,9 @@ int cros_ec_lpc_io_bytes_mec(enum cros_ec_lpc_mec_io_type io_type,
        enum cros_ec_lpc_mec_emi_access_mode access, new_access;
        int ret;
 
+       if (length == 0)
+               return 0;
+
        /* Return checksum of 0 if window is not initialized */
        WARN_ON(mec_emi_base == 0 || mec_emi_end == 0);
        if (mec_emi_base == 0 || mec_emi_end == 0)