mei: bus: enable sending gsc commands

GSC command is and extended header containing a scatter gather
list and without a data buffer. Using MEI_CL_IO_SGL flag,
the caller send the GSC command as a data and the function internally
moves it to the extended header.
Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Cc: Vitaly Lubart <vitaly.lubart@intel.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20220928004145.745803-3-daniele.ceraolospurio@intel.com

drivers/misc/mei/bus.c

@@ -100,9 +100,18 @@ ssize_t __mei_cl_send(struct mei_cl *cl, const u8 *buf, size_t length, u8 vtag,
 	cb->internal = !!(mode & MEI_CL_IO_TX_INTERNAL);
 	cb->blocking = !!(mode & MEI_CL_IO_TX_BLOCKING);
 	memcpy(cb->buf.data, buf, length);
+	/* hack we point data to header */
+	if (mode & MEI_CL_IO_SGL) {
+		cb->ext_hdr = (struct mei_ext_hdr *)cb->buf.data;
+		cb->buf.data = NULL;
+		cb->buf.size = 0;
+	}
 
 	rets = mei_cl_write(cl, cb);
 
+	if (mode & MEI_CL_IO_SGL && rets == 0)
+		rets = length;
+
 out:
 	mutex_unlock(&bus->device_lock);
 
@@ -205,9 +214,16 @@ ssize_t __mei_cl_recv(struct mei_cl *cl, u8 *buf, size_t length, u8 *vtag,
 		goto free;
 	}
 
-	r_length = min_t(size_t, length, cb->buf_idx);
-	memcpy(buf, cb->buf.data, r_length);
+	/* for the GSC type - copy the extended header to the buffer */
+	if (cb->ext_hdr && cb->ext_hdr->type == MEI_EXT_HDR_GSC) {
+		r_length = min_t(size_t, length, cb->ext_hdr->length * sizeof(u32));
+		memcpy(buf, cb->ext_hdr, r_length);
+	} else {
+		r_length = min_t(size_t, length, cb->buf_idx);
+		memcpy(buf, cb->buf.data, r_length);
+	}
 	rets = r_length;
+
 	if (vtag)
 		*vtag = cb->vtag;
 

drivers/misc/mei/mei_dev.h

@@ -116,12 +116,16 @@ enum mei_cb_file_ops {
  * @MEI_CL_IO_TX_INTERNAL: internal communication between driver and FW
  *
  * @MEI_CL_IO_RX_NONBLOCK: recv is non-blocking
+ *
+ * @MEI_CL_IO_SGL: send command with sgl list.
  */
 enum mei_cl_io_mode {
 	MEI_CL_IO_TX_BLOCKING = BIT(0),
 	MEI_CL_IO_TX_INTERNAL = BIT(1),
 
 	MEI_CL_IO_RX_NONBLOCK = BIT(2),
+
+	MEI_CL_IO_SGL         = BIT(3),
 };
 
 /*