On Thu, Jun 13, 2024 at 05:51:39PM +0100, Ben Walsh wrote:
>
> Thanks for fixing this! Unfortunately `in_range` returns -EINVAL if
> length == 0 (see the definition of `fwk_ec_lpc_mec_in_range`). I'm sure
> this broke something in my testing, but I can't find what it was now.
I don't think fwk_ec_lpc_mec_in_range() is upstream. This email is the
only reference I can find to it on the internet.
>
> My original suggestion was to add a test for "length == 0" before the
> "in_range" test, then do the test as you have done. But we decided to
> defer this to a later, separate patch.
>
> There's also a similar "in_range" test in `fwk_ec_lpc_mec_write_bytes`.
>
> We could:
>
> 1. Revert this and change the `data & EC_LPC_STATUS_BUSY_MASK` to
> `res & EC_LPC_STATUS_BUSY_MASK`. This is the same logic as before the
> negative error code change.
>
> or 2. Put in a check for length == 0.
>
> or 3. Change the logic in `fwk_ec_lpc_mec_in_range`. Although I'm not
> sure what the correct answer is to "zero length is in range?"
>
> I prefer option 2. What do you think?
diff --git a/drivers/platform/chrome/cros_ec_lpc_mec.c b/drivers/platform/chrome/cros_ec_lpc_mec.c
index dfad934e65ca..9bf74656164f 100644
--- a/drivers/platform/chrome/cros_ec_lpc_mec.c
+++ b/drivers/platform/chrome/cros_ec_lpc_mec.c
@@ -94,7 +94,7 @@ 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;
+ return 0;
if (WARN_ON(mec_emi_base == 0 || mec_emi_end == 0))
return -EINVAL;
But I don't like how subtle that is. Probably adding a check for
for if (length == 0) to the to cros_ec_lpc_mec_read_bytes() seems
like the best option. I guess option 2 is the best option.
So far as I can see this is the only caller which passes "length == 0"
is in cros_ec_cmd_xfer_lpc().
/* Read response and update checksum */
ret = cros_ec_lpc_ops.read(EC_LPC_ADDR_HOST_PARAM, args.data_size,
^^^^^^^^^^^^^^^
msg->data);
regards,
dan carpenter
