From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Return-Path: MIME-Version: 1.0 In-Reply-To: <1521208314-4783-1-git-send-email-geert@linux-m68k.org> References: <1521208314-4783-1-git-send-email-geert@linux-m68k.org> From: Rob Herring Date: Wed, 4 Apr 2018 19:32:53 -0500 Message-ID: Subject: Re: [PATCH v2 00/21] Allow compile-testing NO_DMA (drivers) Content-Type: text/plain; charset="UTF-8" To: Geert Uytterhoeven Cc: Christoph Hellwig , Marek Szyprowski , Robin Murphy , Felipe Balbi , Greg Kroah-Hartman , "James E . J . Bottomley" , "Martin K . Petersen" , Andrew Morton , Mark Brown , Liam Girdwood , Tejun Heo , Herbert Xu , "David S . Miller" , Bartlomiej Zolnierkiewicz , Stefan Richter , Alan Tull , Moritz Fischer , Wolfram Sang , Jonathan Cameron , Joerg Roedel , Matias Bjorling , Jassi Brar , Mauro Carvalho Chehab , Ulf Hansson , David Woodhouse , Brian Norris , Marek Vasut , Cyrille Pitchen , Boris Brezillon , Richard Weinberger , Kalle Valo , Ohad Ben-Cohen , Bjorn Andersson , Eric Anholt , Stefan Wahren , Linux IOMMU , Linux USB List , linux-scsi@vger.kernel.org, Linux-ALSA , linux-ide@vger.kernel.org, "open list:HARDWARE RANDOM NUMBER GENERATOR CORE" , linux-fbdev@vger.kernel.org, linux1394-devel@lists.sourceforge.net, linux-fpga@vger.kernel.org, Linux I2C , linux-iio@vger.kernel.org, linux-block@vger.kernel.org, linux-media@vger.kernel.org, linux-mmc , linux-mtd@lists.infradead.org, netdev , "open list:REMOTE PROCESSOR (REMOTEPROC) SUBSYSTEM" , "open list:SERIAL DRIVERS" , linux-spi@vger.kernel.org, devel@driverdev.osuosl.org, "linux-kernel@vger.kernel.org" List-ID: On Fri, Mar 16, 2018 at 8:51 AM, Geert Uytterhoeven wrote: > Hi all, > > If NO_DMA=y, get_dma_ops() returns a reference to the non-existing > symbol bad_dma_ops, thus causing a link failure if it is ever used. > > The intention of this is twofold: > 1. To catch users of the DMA API on systems that do no support the DMA > mapping API, > 2. To avoid building drivers that cannot work on such systems anyway. > > However, the disadvantage is that we have to keep on adding dependencies > on HAS_DMA all over the place. > > Thanks to the COMPILE_TEST symbol, lots of drivers now depend on one or > more platform dependencies (that imply HAS_DMA) || COMPILE_TEST, thus > already covering intention #2. Having to add an explicit dependency on > HAS_DMA here is cumbersome, and hinders compile-testing. The same can be said for CONFIG_IOMEM and CONFIG_OF. Any plans to remove those too? CONFIG_IOMEM is mostly just a !CONFIG_UM option. Rob