Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752291AbcDZGTT (ORCPT ); Tue, 26 Apr 2016 02:19:19 -0400 Received: from conssluserg-05.nifty.com ([210.131.2.90]:51709 "EHLO conssluserg-05.nifty.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752245AbcDZGTQ (ORCPT ); Tue, 26 Apr 2016 02:19:16 -0400 DKIM-Filter: OpenDKIM Filter v2.10.3 conssluserg-05.nifty.com u3Q6J4tv023548 X-Nifty-SrcIP: [209.85.161.182] MIME-Version: 1.0 In-Reply-To: <20160425222702.GC29990@codeaurora.org> References: <1461552642-10732-1-git-send-email-yamada.masahiro@socionext.com> <20160425222702.GC29990@codeaurora.org> Date: Tue, 26 Apr 2016 15:19:04 +0900 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH] clk: fix member type of struct clk_hw_onecell_data From: Masahiro Yamada To: Stephen Boyd Cc: linux-clk@vger.kernel.org, Michael Turquette , Linux Kernel Mailing List Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2164 Lines: 85 Hi Stephen, 2016-04-26 7:27 GMT+09:00 Stephen Boyd : > 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? I was misunderstanding. You are right. They are the same. > The latter being a GCC extension while the former being a > C99 standard? Please ignore this patch. Sorry for noise. -- Best Regards Masahiro Yamada