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[79.176.44.197]) by smtp.gmail.com with ESMTPSA id b14sm8512163wrq.47.2020.12.05.11.32.06 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 05 Dec 2020 11:32:08 -0800 (PST) Date: Sat, 5 Dec 2020 14:32:04 -0500 From: "Michael S. Tsirkin" To: "Enrico Weigelt, metux IT consult" Cc: Jason Wang , "Enrico Weigelt, metux IT consult" , linux-kernel@vger.kernel.org, corbet@lwn.net, linus.walleij@linaro.org, bgolaszewski@baylibre.com, linux-doc@vger.kernel.org, linux-gpio@vger.kernel.org, virtualization@lists.linux-foundation.org, linux-riscv@lists.infradead.org, stefanha@redhat.com, msuchanek@suse.de Subject: Re: [PATCH v2 2/2] drivers: gpio: add virtio-gpio guest driver Message-ID: <20201205142218-mutt-send-email-mst@kernel.org> References: <20201203191135.21576-1-info@metux.net> <20201203191135.21576-2-info@metux.net> <8209ce55-a4aa-f256-b9b9-f7eb3cac877b@redhat.com> <96aca1e6-2d5a-deb1-2444-88f938c7a9de@metux.net> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <96aca1e6-2d5a-deb1-2444-88f938c7a9de@metux.net> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Dec 05, 2020 at 08:59:55AM +0100, Enrico Weigelt, metux IT consult wrote: > On 04.12.20 04:35, Jason Wang wrote: > > >> --- a/drivers/gpio/Kconfig > >> +++ b/drivers/gpio/Kconfig > >> @@ -1615,6 +1615,15 @@ config GPIO_MOCKUP > >>         tools/testing/selftests/gpio/gpio-mockup.sh. Reference the > >> usage in > >>         it. > >>   +config GPIO_VIRTIO > >> +    tristate "VirtIO GPIO support" > >> +    depends on VIRTIO > > > > > > Let's use select, since there's no prompt for VIRTIO and it doesn't have > > any dependencies. > > whoops, it's not that simple: > > make: Entering directory '/home/nekrad/src/apu2-dev/pkg/kernel.apu2.git' > make[1]: Entering directory > '/home/nekrad/src/dk/DistroKit/platform-x86_64/build-target/linux-5.8.9-build' > GEN Makefile > drivers/gpu/drm/Kconfig:74:error: recursive dependency detected! > drivers/gpu/drm/Kconfig:74: symbol DRM_KMS_HELPER is selected by > DRM_VIRTIO_GPU > drivers/gpu/drm/virtio/Kconfig:2: symbol DRM_VIRTIO_GPU depends on VIRTIO > drivers/virtio/Kconfig:2: symbol VIRTIO is selected by GPIO_VIRTIO > drivers/gpio/Kconfig:1618: symbol GPIO_VIRTIO depends on GPIOLIB > drivers/gpio/Kconfig:14: symbol GPIOLIB is selected by I2C_MUX_LTC4306 > drivers/i2c/muxes/Kconfig:47: symbol I2C_MUX_LTC4306 depends on I2C > drivers/i2c/Kconfig:8: symbol I2C is selected by FB_DDC > drivers/video/fbdev/Kconfig:63: symbol FB_DDC depends on FB > drivers/video/fbdev/Kconfig:12: symbol FB is selected by DRM_KMS_FB_HELPER > drivers/gpu/drm/Kconfig:80: symbol DRM_KMS_FB_HELPER depends on > DRM_KMS_HELPER > > Seems that we can only depend on or select some symbol - we run into > huge trouble if thats mixed. Just changed DRM_VIRTIO_GPU to just select > VIRIO instead of depending on it, and now it works. > > I've posted another patch for fixing drivers/gpu/drm/virtio/Kconfig > to use 'select' instead of 'depends on'. It seems a bit of a mess, at this point I'm not entirely sure when should drivers select VIRTIO and when depend on it. The text near it says: # SPDX-License-Identifier: GPL-2.0-only config VIRTIO tristate help This option is selected by any driver which implements the virtio bus, such as CONFIG_VIRTIO_PCI, CONFIG_VIRTIO_MMIO, CONFIG_RPMSG or CONFIG_S390_GUEST. Which seems clear enough and would indicate drivers for devices *behind* the bus should not select VIRTIO and thus presumably should "depend on" it. This is violated in virtio console and virtio fs drivers. For console it says: commit 9f30eb29c514589e16f2999ea070598583d1f6ec Author: Michal Suchanek Date: Mon Aug 31 18:58:50 2020 +0200 char: virtio: Select VIRTIO from VIRTIO_CONSOLE. Make it possible to have virtio console built-in when other virtio drivers are modular. Signed-off-by: Michal Suchanek Reviewed-by: Amit Shah Link: https://lore.kernel.org/r/20200831165850.26163-1-msuchanek@suse.de Signed-off-by: Greg Kroah-Hartman which seems kind of bogus - why do we care about allowing a builtin virtio console driver if the pci virtio bus driver is a module? There won't be any devices on the bus to attach to ... And for virtio fs it was like this from the beginning. I am inclined to fix console and virtio fs to depend on VIRTIO: select is harder to use correctly ... Jason? > -- > --- > Hinweis: unverschlüsselte E-Mails können leicht abgehört und manipuliert > werden ! Für eine vertrauliche Kommunikation senden Sie bitte ihren > GPG/PGP-Schlüssel zu. > --- > Enrico Weigelt, metux IT consult > Free software and Linux embedded engineering > info@metux.net -- +49-151-27565287