From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.5 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id BFB56C67839 for ; Tue, 11 Dec 2018 21:42:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 742FE2086D for ; Tue, 11 Dec 2018 21:42:47 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="AhmZsB90" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 742FE2086D Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726295AbeLKVmq (ORCPT ); Tue, 11 Dec 2018 16:42:46 -0500 Received: from mail-wr1-f68.google.com ([209.85.221.68]:33475 "EHLO mail-wr1-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726146AbeLKVmp (ORCPT ); Tue, 11 Dec 2018 16:42:45 -0500 Received: by mail-wr1-f68.google.com with SMTP id c14so15679841wrr.0 for ; Tue, 11 Dec 2018 13:42:44 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=GCrTx0GUT9bWAAZLsSM3h1m0z1OkU0xgKVx7hXy90W4=; b=AhmZsB905uTQXGpZTrM3q5a4dLgAm2NX2C0g/F4KOsayo7BucRYl8P42Db3kZ8GCzR fYuKpgU4prQDv0jYHePZXyczwrus3KfgEotvbbykMqs6fm9EXaACLrHuNwaJZyA4S5bE dsKDnyHwOp4aivjW3iJaz/32lcVd3Hu6o04G0LhslUweWmGUrwgqjGDZJZnInVw9mte8 1o7/ODPo1p2eq2okSwPlSDHLOfw+E6qRmZtLuL2hlp9dUI6L44oEktW99s9mEtyEeFe7 /JpJIqEuA1JLcAcUZMfc3mNkhHaybOn5GFXErfszYhSeR1C8SX5sJwG3oSrY74SpAL8Z YmSw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=GCrTx0GUT9bWAAZLsSM3h1m0z1OkU0xgKVx7hXy90W4=; b=Dfk9Pt6VGB64V9tI8VpVlBDIM9POqeavJSTy73pIAn3IBp1He/WT+35OxdKHJTwpX2 JE+c0QhGezwJTojDs4/YhK6TwHOR8W4e2VLyyAIAZ6bGcGK4z7duhFWZHMg+vo36S3p5 eap92mYLQZrRnTgQMdpmfIK3SQ09ptwHT7Nsi2O4a8dDjGOpQJWY6AGMSQGlt0BCOjsb sSEFhozHJQ2P/ZCIJ8okuR7xG4Pgnsv+2pebr5kQMhKvyC3VrAW2xeIE0raZjANeeZ+0 bAIFI8wk7sanZUf10uI95vTDZDn1/dtfTYhKblspsJ/h4ECFQSLLXeJTErHWejRZpxxr 03bg== X-Gm-Message-State: AA+aEWZzg9KU8BrqDzoDY6mH2qLhV2KMkQlCvHjP5K0iT7Wph++Fv54e 6PcQNbi1cH+Qc+EPC2DQLY66MNv+Txm0gw== X-Google-Smtp-Source: AFSGD/VUBKn7KMlf/NUFyJ+vO4YK3qnR5M3AO5KbI4rWUK6QaeY7HaMIWu1U7fa/N/woIaz3OQ/n+Q== X-Received: by 2002:adf:df01:: with SMTP id y1mr15736777wrl.127.1544564562916; Tue, 11 Dec 2018 13:42:42 -0800 (PST) Received: from flashbox ([2a01:4f8:10b:24a5::2]) by smtp.gmail.com with ESMTPSA id t76sm1553105wme.33.2018.12.11.13.42.42 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Tue, 11 Dec 2018 13:42:42 -0800 (PST) Date: Tue, 11 Dec 2018 14:42:40 -0700 From: Nathan Chancellor To: Nick Desaulniers Cc: Harry Wentland , sunpeng.li@amd.com, alexander.deucher@amd.com, christian.koenig@amd.com, David1.Zhou@amd.com, amd-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, LKML Subject: Re: [PATCH] drm/amd/display: Pass app_tf by value rather than by reference Message-ID: <20181211214240.GA31705@flashbox> References: <20181210234201.4850-1-natechancellor@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.11.1 (2018-12-01) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Dec 11, 2018 at 01:25:00PM -0800, Nick Desaulniers wrote: > On Mon, Dec 10, 2018 at 3:42 PM Nathan Chancellor > wrote: > > > > Clang warns when an expression that equals zero is used as a null > > pointer constant (in lieu of NULL): > > > > drivers/gpu/drm/amd/amdgpu/../display/amdgpu_dm/amdgpu_dm.c:4435:3: > > warning: expression which evaluates to zero treated as a null pointer > > constant of type 'const enum color_transfer_func *' > > [-Wnon-literal-null-conversion] > > TRANSFER_FUNC_UNKNOWN, > > ^~~~~~~~~~~~~~~~~~~~~ > > 1 warning generated. > > > > This warning is caused by commit bb47de736661 ("drm/amdgpu: Set FreeSync > > state using drm VRR properties") and it could be solved by using NULL > > instead of TRANSFER_FUNC_UNKNOWN or casting TRANSFER_FUNC_UNKNOWN as a > > pointer. However, after looking into it, there doesn't appear to be a > > good reason to pass app_tf by reference as it is never mutated along the > > way. This is the only code path in which app_tf is used: > > > > mod_freesync_build_vrr_infopacket -> > > build_vrr_infopacket_v2 -> > > build_vrr_infopacket_fs2_data > > > > Neither mod_freesync_build_vrr_infopacket or build_vrr_infopacket_v2 > > modify app_tf's value and build_vrr_infopacket_fs2_data expects just > > the value so we can avoid dereferencing anything by just passing in > > app_tf's value to mod_freesync_build_vrr_infopacket and > > build_vrr_infopacket_v2. > > > > There is no functional change because build_vrr_infopacket_fs2_data > > doesn't do anything if TRANSFER_FUNC_UNKNOWN is passed to it, the same > > as not calling build_vrr_infopacket_fs2_data at all like before this > > change when NULL was used for app_tf. > > Nathan, > Thanks for sending this patch. I was hoping to provide review sooner, > but have been quite busy lately. > Late review is better than no review, I appeciate you taking the time to do this! > Yeah, especially for LP64 targets, the pointer to enum is larger than > just the enum, and if it's not being updated ("in/out paramter") > there's no need to pass by pointer. > Thanks for confirming! > > > > Signed-off-by: Nathan Chancellor > > --- > > drivers/gpu/drm/amd/display/modules/freesync/freesync.c | 7 +++---- > > drivers/gpu/drm/amd/display/modules/inc/mod_freesync.h | 2 +- > > 2 files changed, 4 insertions(+), 5 deletions(-) > > > > diff --git a/drivers/gpu/drm/amd/display/modules/freesync/freesync.c b/drivers/gpu/drm/amd/display/modules/freesync/freesync.c > > index 620a171620ee..520665a9d81a 100644 > > --- a/drivers/gpu/drm/amd/display/modules/freesync/freesync.c > > +++ b/drivers/gpu/drm/amd/display/modules/freesync/freesync.c > > @@ -656,7 +656,7 @@ static void build_vrr_infopacket_v1(enum signal_type signal, > > > > static void build_vrr_infopacket_v2(enum signal_type signal, > > const struct mod_vrr_params *vrr, > > - const enum color_transfer_func *app_tf, > > + enum color_transfer_func app_tf, > > struct dc_info_packet *infopacket) > > { > > unsigned int payload_size = 0; > > @@ -664,8 +664,7 @@ static void build_vrr_infopacket_v2(enum signal_type signal, > > build_vrr_infopacket_header_v2(signal, infopacket, &payload_size); > > build_vrr_infopacket_data(vrr, infopacket); > > > > - if (app_tf != NULL) > > - build_vrr_infopacket_fs2_data(*app_tf, infopacket); > > + build_vrr_infopacket_fs2_data(app_tf, infopacket); > > > > build_vrr_infopacket_checksum(&payload_size, infopacket); > > > > @@ -676,7 +675,7 @@ void mod_freesync_build_vrr_infopacket(struct mod_freesync *mod_freesync, > > const struct dc_stream_state *stream, > > const struct mod_vrr_params *vrr, > > enum vrr_packet_type packet_type, > > - const enum color_transfer_func *app_tf, > > + enum color_transfer_func app_tf, > > struct dc_info_packet *infopacket) > > { > > /* SPD info packet for FreeSync */ > > diff --git a/drivers/gpu/drm/amd/display/modules/inc/mod_freesync.h b/drivers/gpu/drm/amd/display/modules/inc/mod_freesync.h > > index 949a8b62aa98..063af6258fd9 100644 > > --- a/drivers/gpu/drm/amd/display/modules/inc/mod_freesync.h > > +++ b/drivers/gpu/drm/amd/display/modules/inc/mod_freesync.h > > @@ -145,7 +145,7 @@ void mod_freesync_build_vrr_infopacket(struct mod_freesync *mod_freesync, > > const struct dc_stream_state *stream, > > const struct mod_vrr_params *vrr, > > enum vrr_packet_type packet_type, > > - const enum color_transfer_func *app_tf, > > + enum color_transfer_func app_tf, > > Don't you need to update the callsite of `mod_freesync_build_vrr_infopacket` in > > drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c#4949: > > - NULL, > + transfer_func_unknown, > That change in commit bb47de736661 ("drm/amdgpu: Set FreeSync state using drm VRR properties") in -next is what prompted this patch (the warning in the commit message is not present in mainline): mod_freesync_build_vrr_infopacket( dm->freesync_module, new_stream, &vrr, packet_type_vrr, transfer_func_unknown, &vrr_infopacket); > Maybe at that point the `if (app_tf != NULL)` could be replaced with > `if (app_tf != transfer_func_unknown)` hoisted from > `build_vrr_infopacket_fs2_data`? (There's only one caller of > `build_vrr_infopacket_fs2_data` today, maybe fine to leave the > unconditional call and check). > Hmmm that's not unreasonable I suppose. I guess it depends on if build_vrr_infopacket_fs2_data could ever be called from outside of build_vrr_infopacket_v2; if it can, it makes sense to leave the conditional check for 'app_tf != transfer_func_unknown' in build_vrr_infopacket_fs2_data and leaving the unconditional call to it in build_vrr_infopacket_v2 (since app_tf is no longer a pointer, no need to check against NULL). I'm happy to do a v2 if the maintainers feel strongly about it, thank you for bringing that up. > Either way, I suspect without the change to > drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c, that this fails to > compile? Correct so this is targeted at -next, rather than mainline, probably should get in the habit of adding '-next' to my patch subjects... > -- > Thanks, > ~Nick Desaulniers Thank you for the review! Nathan