linux-kernel - [PATCH] platform/chrome: cros_ec_lpc: Handle zero length read/write

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Date: Thu, 13 Jun 2024 22:25:42 +0100
From: Ben Walsh <ben@...nut.com>
To: Dan Carpenter <dan.carpenter@...aro.org>,
	Benson Leung <bleung@...omium.org>,
	Tzung-Bi Shih <tzungbi@...nel.org>,
	Guenter Roeck <groeck@...omium.org>,
	chrome-platform@...ts.linux.dev,
	linux-kernel@...r.kernel.org,
	kernel-janitors@...r.kernel.org
Cc: Ben Walsh <ben@...nut.com>
Subject: [PATCH] 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.

Signed-off-by: Ben Walsh <ben@...nut.com>
---
 drivers/platform/chrome/cros_ec_lpc_mec.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/platform/chrome/cros_ec_lpc_mec.c b/drivers/platform/chrome/cros_ec_lpc_mec.c
index dfad934e65ca..a56584171168 100644
--- 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)

base-commit: 77a714325d09e1527d865dc011ef91c4972ffedd
-- 
2.45.1