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Thu, 8 Apr 2021 10:37:05 +0000 (UTC) Received: from [10.36.114.231] (ovpn-114-231.ams2.redhat.com [10.36.114.231]) by smtp.corp.redhat.com (Postfix) with ESMTP id 7A5151001B2C; Thu, 8 Apr 2021 10:37:00 +0000 (UTC) Subject: Re: [PATCH v1 2/2] drivers/gpu/drm: don't select DMA_CMA or CMA from aspeed or etnaviv From: David Hildenbrand To: Arnd Bergmann Cc: Linux Kernel Mailing List , Linux-MM , Joel Stanley , David Airlie , Daniel Vetter , Andrew Jeffery , Lucas Stach , Russell King , Christian Gmeiner , Mike Rapoport , Bartlomiej Zolnierkiewicz , Linus Walleij , Michal Simek , Masahiro Yamada , Randy Dunlap , Peter Collingbourne , linux-aspeed , dri-devel , Linux ARM , The etnaviv authors , Linux Fbdev development list References: <20210408092011.52763-1-david@redhat.com> <20210408092011.52763-3-david@redhat.com> Organization: Red Hat GmbH Message-ID: <0b1928a8-99c3-f1f1-ad66-40145199d9bc@redhat.com> Date: Thu, 8 Apr 2021 12:36:59 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.1 MIME-Version: 1.0 In-Reply-To: Content-Language: en-US X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210408_113713_724505_BD7366A2 X-CRM114-Status: GOOD ( 26.25 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 08.04.21 12:27, David Hildenbrand wrote: > On 08.04.21 12:20, Arnd Bergmann wrote: >> On Thu, Apr 8, 2021 at 11:22 AM David Hildenbrand wrote: >>> >>> Random drivers should not override a user configuration of core knobs >>> (e.g., CONFIG_DMA_CMA=n). Use "imply" instead, to still respect >>> dependencies and manual overrides. >>> >>> "This is similar to "select" as it enforces a lower limit on another >>> symbol except that the "implied" symbol's value may still be set to n >>> from a direct dependency or with a visible prompt." >>> >>> Implying DRM_CMA should be sufficient, as that depends on CMA. >>> >>> Note: If this is a real dependency, we should use "depends on DMA_CMA" >>> instead - but I assume the driver can work without CMA just fine -- >>> esp. when we wouldn't have HAVE_DMA_CONTIGUOUS right now. >> >> 'imply' is almost never the right solution, and it tends to cause more >> problems than it solves. > > I thought that was the case with "select" :) > >> >> In particular, it does not prevent a configuration with 'DRM_CMA=m' > > I assume you meant "DRM_CMA=n" ? DRM_CMA cannot be built as a module. > >> and 'DRMA_ASPEED_GFX=y', or any build failures from such >> a configuration. > > I don't follow. "DRM_CMA=n" and 'DRMA_ASPEED_GFX=y' is supposed to work > just fine (e.g., without HAVE_DMA_CONTIGUOUS) or what am I missing? > >> >> If you want this kind of soft dependency, you need >> 'depends on DRM_CMA || !DRM_CMA'. > > Seriously? I think the point of imply is "please enable if possible and > not prevented by someone else". Your example looks more like a NOP - no? > Or will it have the same effect? I just tried (remove CONFIG_DMA_CMA from .config followed by make) and the default will be set to "N" (when querying the user). So it indeed looks like a NOP - unless I am missing something. -- Thanks, David / dhildenb _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel