Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751848AbcDYW1J (ORCPT ); Mon, 25 Apr 2016 18:27:09 -0400 Received: from smtp.codeaurora.org ([198.145.29.96]:49825 "EHLO smtp.codeaurora.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751089AbcDYW1G (ORCPT ); Mon, 25 Apr 2016 18:27:06 -0400 Date: Mon, 25 Apr 2016 15:27:02 -0700 From: Stephen Boyd To: Masahiro Yamada Cc: linux-clk@vger.kernel.org, Michael Turquette , linux-kernel@vger.kernel.org Subject: Re: [PATCH] clk: fix member type of struct clk_hw_onecell_data Message-ID: <20160425222702.GC29990@codeaurora.org> References: <1461552642-10732-1-git-send-email-yamada.masahiro@socionext.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1461552642-10732-1-git-send-email-yamada.masahiro@socionext.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1982 Lines: 68 On 04/25, Masahiro Yamada wrote: > We cannot assign any value to an array type variable. So, > > hw_data->hws = kcalloc(hw_data->num, sizeof(struct clk_hw *), > GFP_KERNEL); > > fails with "invalid use of flexible array member" error. That's good. We don't want assignment to the hws member of this structure to happen from an allocation like kcalloc. > > There are two ways to fix this issue. > > [1] Make it a double-pointer > struct clk_hw_onecell_data { > size_t num; > struct clk_hw **hws; > }; > > This works as struct clk_onecell_data does. True we could go back to the old style with two allocations. > > [2] Make it a zero-sized array > struct clk_hw_onecell_data { > size_t num; > struct clk_hw *hws[0]; > }; > > This allows one-shot memory allocation like this: > > hw_data = kmalloc(sizeof(*hw_data) + clk_num * sizeof(struct clk_hw *), > GFP_KERNEL); > Good, that was possible before this patch wasn't it? > This commit adopts [2] because it looks like Stephen's intention > (he moved hws[] to the bottom of struct clk_hw_onecell_data). > > Fixes: 0861e5b8cf80 ("clk: Add clk_hw OF clk providers") > Signed-off-by: Masahiro Yamada > --- > > include/linux/clk-provider.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/include/linux/clk-provider.h b/include/linux/clk-provider.h > index fd2ccd5..1850e25 100644 > --- a/include/linux/clk-provider.h > +++ b/include/linux/clk-provider.h > @@ -769,7 +769,7 @@ struct clk_onecell_data { > > struct clk_hw_onecell_data { > size_t num; > - struct clk_hw *hws[]; > + struct clk_hw *hws[0]; I'm totally lost now. Isn't a flex array with [] or with [0] the same? The latter being a GCC extension while the former being a C99 standard? -- Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project