misc: fastrpc: Add helper function to get list and page

Add helper functions to get invoke buffer and page start pointers.

Signed-off-by: Vamsi Krishna Gattupalli <quic_vgattupa@quicinc.com>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Link: https://lore.kernel.org/r/20220214161002.6831-10-srinivas.kandagatla@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/misc/fastrpc.c

@@ -833,6 +833,16 @@ static int fastrpc_create_maps(struct fastrpc_invoke_ctx *ctx)
 	return 0;
 }
 
+static struct fastrpc_invoke_buf *fastrpc_invoke_buf_start(union fastrpc_remote_arg *pra, int len)
+{
+	return (struct fastrpc_invoke_buf *)(&pra[len]);
+}
+
+static struct fastrpc_phy_page *fastrpc_phy_page_start(struct fastrpc_invoke_buf *buf, int len)
+{
+	return (struct fastrpc_phy_page *)(&buf[len]);
+}
+
 static int fastrpc_get_args(u32 kernel, struct fastrpc_invoke_ctx *ctx)
 {
 	struct device *dev = ctx->fl->sctx->dev;
@@ -860,9 +870,8 @@ static int fastrpc_get_args(u32 kernel, struct fastrpc_invoke_ctx *ctx)
 		return err;
 
 	rpra = ctx->buf->virt;
-	list = ctx->buf->virt + ctx->nscalars * sizeof(*rpra);
-	pages = ctx->buf->virt + ctx->nscalars * (sizeof(*list) +
-		sizeof(*rpra));
+	list = fastrpc_invoke_buf_start(rpra, ctx->nscalars);
+	pages = fastrpc_phy_page_start(list, ctx->nscalars);
 	args = (uintptr_t)ctx->buf->virt + metalen;
 	rlen = pkt_size - metalen;
 	ctx->rpra = rpra;