platform/chrome: cros_ec_proto: Introduce cros_ec_get_cmd_versions()

Retrieving the supported versions of a command is a fairly common
operation. Provide a helper for it.

If the command is not supported at all the EC returns
-EINVAL/EC_RES_INVALID_PARAMS.

This error is translated into an empty version mask as that is easier to
handle for callers and they don't need to know about the error details.

Signed-off-by: Thomas Weißschuh <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Tzung-Bi Shih <[email protected]>

Author: t-8ch

drivers/platform/chrome/cros_ec_proto.c

@@ -5,6 +5,7 @@
 
 #include <linux/delay.h>
 #include <linux/device.h>
+#include <linux/limits.h>
 #include <linux/module.h>
 #include <linux/platform_data/cros_ec_commands.h>
 #include <linux/platform_data/cros_ec_proto.h>
@@ -1069,3 +1070,37 @@ int cros_ec_cmd_readmem(struct cros_ec_device *ec_dev, u8 offset, u8 size, void
 			   &params, sizeof(params), dest, size);
 }
 EXPORT_SYMBOL_GPL(cros_ec_cmd_readmem);
+
+/**
+ * cros_ec_get_cmd_versions - Get supported version mask.
+ *
+ * @ec_dev: EC device
+ * @cmd: Command to test
+ *
+ * Return: version mask on success, negative error number on failure.
+ */
+int cros_ec_get_cmd_versions(struct cros_ec_device *ec_dev, u16 cmd)
+{
+	struct ec_params_get_cmd_versions req_v0;
+	struct ec_params_get_cmd_versions_v1 req_v1;
+	struct ec_response_get_cmd_versions resp;
+	int ret;
+
+	if (cmd <= U8_MAX) {
+		req_v0.cmd = cmd;
+		ret = cros_ec_cmd(ec_dev, 0, EC_CMD_GET_CMD_VERSIONS,
+				  &req_v0, sizeof(req_v0), &resp, sizeof(resp));
+	} else {
+		req_v1.cmd = cmd;
+		ret = cros_ec_cmd(ec_dev, 1, EC_CMD_GET_CMD_VERSIONS,
+				  &req_v1, sizeof(req_v1), &resp, sizeof(resp));
+	}
+
+	if (ret == -EINVAL)
+		return 0; /* Command not implemented */
+	else if (ret < 0)
+		return ret;
+	else
+		return resp.version_mask;
+}
+EXPORT_SYMBOL_GPL(cros_ec_get_cmd_versions);

include/linux/platform_data/cros_ec_proto.h

@@ -263,6 +263,8 @@ int cros_ec_cmd(struct cros_ec_device *ec_dev, unsigned int version, int command
 
 int cros_ec_cmd_readmem(struct cros_ec_device *ec_dev, u8 offset, u8 size, void *dest);
 
+int cros_ec_get_cmd_versions(struct cros_ec_device *ec_dev, u16 cmd);
+
 /**
  * cros_ec_get_time_ns() - Return time in ns.
  *