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[84.226.167.205]) by smtp.googlemail.com with ESMTPSA id b127sm22859713wmc.45.2020.12.21.13.04.24 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 21 Dec 2020 13:04:25 -0800 (PST) Date: Mon, 21 Dec 2020 22:04:23 +0100 From: Krzysztof Kozlowski To: John Stultz Cc: Greg Kroah-Hartman , Serge Semin , Felipe Balbi , Florian Fainelli , Rob Herring , Wei Xu , "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" , linux-arm-kernel , Serge Semin , lkml , YongQin Liu , Amit Pundir , Todd Kjos Subject: Re: [PATCH v2 16/18] arm64: dts: hi3660: Harmonize DWC USB3 DT nodes name Message-ID: <20201221210423.GA2504@kozik-lap> References: <20201111091552.15593-1-Sergey.Semin@baikalelectronics.ru> <20201111091552.15593-17-Sergey.Semin@baikalelectronics.ru> <20201219110603.GA8061@kozik-lap> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Dec 21, 2020 at 12:24:11PM -0800, John Stultz wrote: > On Sat, Dec 19, 2020 at 3:06 AM Krzysztof Kozlowski wrote: > > On Fri, Dec 18, 2020 at 09:11:42PM -0800, John Stultz wrote: > > > On Wed, Nov 11, 2020 at 1:22 AM Serge Semin > > > wrote: > > > > > > > > In accordance with the DWC USB3 bindings the corresponding node > > > > name is suppose to comply with the Generic USB HCD DT schema, which > > > > requires the USB nodes to have the name acceptable by the regexp: > > > > "^usb(@.*)?" . Make sure the "snps,dwc3"-compatible nodes are correctly > > > > named. > > > > > > > > Signed-off-by: Serge Semin > > > > Acked-by: Krzysztof Kozlowski > > > > --- > > > > arch/arm64/boot/dts/hisilicon/hi3660.dtsi | 2 +- > > > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > > > > > diff --git a/arch/arm64/boot/dts/hisilicon/hi3660.dtsi b/arch/arm64/boot/dts/hisilicon/hi3660.dtsi > > > > index d25aac5e0bf8..aea3800029b5 100644 > > > > --- a/arch/arm64/boot/dts/hisilicon/hi3660.dtsi > > > > +++ b/arch/arm64/boot/dts/hisilicon/hi3660.dtsi > > > > @@ -1166,7 +1166,7 @@ usb_phy: usb-phy { > > > > }; > > > > }; > > > > > > > > - dwc3: dwc3@ff100000 { > > > > + dwc3: usb@ff100000 { > > > > compatible = "snps,dwc3"; > > > > reg = <0x0 0xff100000 0x0 0x100000>; > > > > > > > > > Oof. So this patch is breaking the usb gadget functionality on HiKey960 w/ AOSP. > > > > > > In order to choose the right controller for gadget mode with AOSP, one > > > sets the "sys.usb.controller" property, which until now for HiKey960 > > > has been "ff100000.dwc3". > > > After this patch, the controller isn't found and we would have to > > > change userland to use "ff100000.usb", which would then break booting > > > on older kernels (testing various LTS releases on AOSP is one of the > > > key uses of the HiKey960). > > > > > > So while I understand the desire to unify the schema, as HiKey960 > > > really isn't likely to be used outside of AOSP, I wonder if reverting > > > this one change is in the best interest of not breaking existing > > > userland? > > > > The node names are not part of an ABI, are they? I expect only > > compatibles and properties to be stable. If user-space looks for > > something by name, it's a user-space's mistake. Not mentioning that you > > also look for specific address... Imagine remapping of addresses with > > ranges (for whatever reason) - AOSP also would be broken? Addresses are > > definitely not an ABI. > > Though that is how it's exported through sysfs. The ABI is the format of sysfs file for example in /sys/devices. However the ABI is not the exact address or node name of each device. > In AOSP it is then used to setup the configfs gadget by writing that > value into /config/usb_gadget/g1/UDC. > > Given there may be multiple controllers on a device, or even if its > just one and the dummy hcd driver is enabled, I'm not sure how folks > reference the "right" one without the node name? I think it is the same type of problem as for all other subsystems, e.g. mmc, hwmon/iio. They usually solve it either with aliases or with special property with the name/label. > I understand the fuzziness with sysfs ABI, and I get that having > consistent naming is important, but like the eth0 -> enp3s0 changes, > it seems like this is going to break things. One could argue whether interface name is or is not ABI. But please tell me how the address of a device in one's representation (for example DT) is a part of a stable interface? > Greg? Is there some better way AOSP should be doing this? If you need to find specific device, maybe go through the given bus and check compatibles? Best regards, Krzysztof