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From: Armin Wolf <W_Armin@gmx.de>
To: hdegoede@redhat.com,
	ilpo.jarvinen@linux.intel.com
Cc: rafael@kernel.org,
	lenb@kernel.org,
	linux-acpi@vger.kernel.org,
	platform-driver-x86@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: [PATCH v3 1/2] platform/x86: wmi: Support reading/writing 16 bit EC values
Date: Fri,  8 Mar 2024 20:50:26 +0100
Message-Id: <20240308195027.7640-1-W_Armin@gmx.de>
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The ACPI EC address space handler currently only supports
reading/writing 8 bit values. Some firmware implementations however
want to access for example 16 bit values, which is prefectly legal
according to the ACPI spec.

Add support for reading/writing such values.

Tested on a Dell Inspiron 3505 and a Asus Prime B650-Plus.

Signed-off-by: Armin Wolf <W_Armin@gmx.de>
=2D--
Chnages since v2:
- fix address overflow check

Changes since v1:
- use BITS_PER_BYTE
- validate that number of bytes to read/write does not overflow the
  address
=2D--
 drivers/platform/x86/wmi.c | 47 ++++++++++++++++++++++++++++++--------
 1 file changed, 37 insertions(+), 10 deletions(-)

diff --git a/drivers/platform/x86/wmi.c b/drivers/platform/x86/wmi.c
index 1920e115da89..e6cab1cf611a 100644
=2D-- a/drivers/platform/x86/wmi.c
+++ b/drivers/platform/x86/wmi.c
@@ -1153,6 +1153,32 @@ static int parse_wdg(struct device *wmi_bus_dev, st=
ruct platform_device *pdev)
 	return 0;
 }

+static int ec_read_multiple(u8 address, u8 *buffer, size_t bytes)
+{
+	int i, ret;
+
+	for (i =3D 0; i < bytes; i++) {
+		ret =3D ec_read(address + i, &buffer[i]);
+		if (ret < 0)
+			return ret;
+	}
+
+	return 0;
+}
+
+static int ec_write_multiple(u8 address, u8 *buffer, size_t bytes)
+{
+	int i, ret;
+
+	for (i =3D 0; i < bytes; i++) {
+		ret =3D ec_write(address + i, buffer[i]);
+		if (ret < 0)
+			return ret;
+	}
+
+	return 0;
+}
+
 /*
  * WMI can have EmbeddedControl access regions. In which case, we just wa=
nt to
  * hand these off to the EC driver.
@@ -1162,27 +1188,28 @@ acpi_wmi_ec_space_handler(u32 function, acpi_physi=
cal_address address,
 			  u32 bits, u64 *value,
 			  void *handler_context, void *region_context)
 {
-	int result =3D 0;
-	u8 temp =3D 0;
+	int bytes =3D bits / BITS_PER_BYTE;
+	int ret;
+
+	if (!value)
+		return AE_NULL_ENTRY;

-	if ((address > 0xFF) || !value)
+	if (!bytes || bytes > sizeof(*value))
 		return AE_BAD_PARAMETER;

-	if (function !=3D ACPI_READ && function !=3D ACPI_WRITE)
+	if (address > U8_MAX || address + bytes - 1 > U8_MAX)
 		return AE_BAD_PARAMETER;

-	if (bits !=3D 8)
+	if (function !=3D ACPI_READ && function !=3D ACPI_WRITE)
 		return AE_BAD_PARAMETER;

 	if (function =3D=3D ACPI_READ) {
-		result =3D ec_read(address, &temp);
-		*value =3D temp;
+		ret =3D ec_read_multiple(address, (u8 *)value, bytes);
 	} else {
-		temp =3D 0xff & *value;
-		result =3D ec_write(address, temp);
+		ret =3D ec_write_multiple(address, (u8 *)value, bytes);
 	}

-	switch (result) {
+	switch (ret) {
 	case -EINVAL:
 		return AE_BAD_PARAMETER;
 	case -ENODEV:
=2D-
2.39.2