From: Bjorn Andersson <bjorn.andersson@linaro.org>
To: Serge Semin <fancer.lancer@gmail.com>
Cc: John Stultz <john.stultz@linaro.org>,
Serge Semin <Sergey.Semin@baikalelectronics.ru>,
Krzysztof Kozlowski <krzk@kernel.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Rob Herring <robh+dt@kernel.org>, Felipe Balbi <balbi@kernel.org>,
Florian Fainelli <f.fainelli@gmail.com>,
Andy Gross <agross@kernel.org>,
"open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS"
<devicetree@vger.kernel.org>,
linux-arm-msm <linux-arm-msm@vger.kernel.org>,
Linux USB List <linux-usb@vger.kernel.org>,
lkml <linux-kernel@vger.kernel.org>,
linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
Amit Pundir <amit.pundir@linaro.org>
Subject: Re: [PATCH 29/29] arm64: dts: qcom: Harmonize DWC USB3 DT nodes name
Date: Tue, 17 Aug 2021 22:44:23 -0500 [thread overview]
Message-ID: <YRyCFx0ZOYTMhinf@builder.lan> (raw)
In-Reply-To: <20210815194617.sbrkutxzldqbxfat@mobilestation>
On Sun 15 Aug 14:46 CDT 2021, Serge Semin wrote:
> Hello John
>
> On Fri, Aug 13, 2021 at 06:06:24PM -0700, John Stultz wrote:
> > On Thu, Jul 22, 2021 at 3:09 PM Serge Semin <fancer.lancer@gmail.com> wrote:
> > > On Thu, Jul 22, 2021 at 01:09:05PM -0700, John Stultz wrote:
> > > > On Thu, Jul 22, 2021 at 12:17 PM Bjorn Andersson
> > > > <bjorn.andersson@linaro.org> wrote:
> > > > > > On Jul 21, 2021, 1:45 PM +0200, Krzysztof Kozlowski wrote:
> > > > > > > I had impression that kernel defines interfaces which should be used and
> > > > > > > are stable (e.g. syscalls, sysfs and so on). This case is example of
> > > > > > > user-space relying on something not being marked as part of ABI. Instead
> > > > > > > they found something working for them and now it is being used in "we
> > > > > > > cannot break existing systems". Basically, AOSP unilaterally created a
> > > > > > > stable ABI and now kernel has to stick to it.
> > > > > > >
> > > > > > > Really, all normal systems depend on aliases or names and here we have
> > > > > > > dependency on device address. I proposed way how AOSP should be fixed.
> > > > > > > Anything happened? Nope.
> > > > > >
> > > > > > First time he sent a possible solution for the problem:
> > > > > > https://lore.kernel.org/lkml/20201221210423.GA2504@kozik-lap/
> > > > > >
> > > > > > To sum up you could have used one of the more portable approaches
> > > > > > 1. add an udc alias to the controller and use it then to refer to the
> > > > > > corresponding USB controller
> > > > >
> > > > > Is there such a thing as "UDC alias"? Or are you suggesting that we
> > > > > should add such feature?
> > > > >
> > > > > I think it would be wonderful if we could identify the UDCs on our
> > > > > boards as "USB1" and "USB2", or "the one and only USB-C connector". But
> > > > > unless that will fall back to the existing naming it would break John's
> > > > > _existing_ userspace.
> > > >
> > >
> > > > Well, I'd not hold up the existing userspace I'm using as sacrosanct
> > > > (AOSP devices still usually don't have to work cross-kernel versions -
> > > > devboards being the main exception). I'm fine if we can rework
> > > > userland as proposed, so that the issues can be avoided, but I
> > > > honestly don't have enough context to really understand what that
> > > > looks like (no idea what udc aliases are).
> > > >
> > > > And whatever we do, the main constraint is that userland has to be
> > > > able to work with existing LTS kernels and newer kernels.
> > >
> > > As I said in my response to Bjorn even if it is added to the kernel it
> > > won't get to the official LTSes as it would be a new kernel feature.
> > > New features aren't normally backported to the older kernels.
> > >
> > > >
> > > > > > 2. search through DT-nodes looking for a specific compatible/reg
> > > > > > DT-properties.
> > > > > >
> > > > >
> > > > > We could define that this is the way, but again we didn't yesterday so
> > > > > your proposal is not backwards compatible.
> > > >
> > >
> > > > It may be backwards compatible, but I'm still not clear exactly how it
> > > > would work.
> > > >
> > > > I guess if we look through all
> > > > sys/bus/platform/devices/*/of_node/compatbile strings for the desired
> > > > "snps,dwc3", then find which of the directories have the desired
> > > > address in the string? (The suggestion for looking at reg seems
> > > > better, but I don't get a char value out of the dwc3 of_node/reg
> > > > file).
> > >
> > > The algorithm is simple:
> > > 1) You know what USB controllers you have on your platform. They are
> > > supposed to be compatible with snps,dwc3 string and have some pre-defined
> > > base address.
> > > 2) Find all the files in the directory /sys/class/udc/.
> > > 3) Walk through all the directories in /sys/bus/platform/devices/ with
> > > names found in 2) and stop on the device with matching compatible/base
> > > address defined in 1).
> > >
> > > In my case the strings could be retrieved like this:
> > > USB_NAME_COMPAT=$(/sys/bus/platform/devices/1f100000.usb/of_node/compatible | tr '\0' '\t' | cut -f1)
> > > USB_DEVICE_ADDR="$(head -c 4 /sys/bus/platform/devices/1f100000.usb/of_node/reg | hexdump -ve '/1 "%02x"' | sed -e 's/^0*//g')"
> >
> >
>
> > Hey Serge,
> > I just wanted to follow up here. Amit has reworked the db845c AOSP
> > userland so that it no longer uses the fixed node name, but instead
> > probes for it:
> > https://android-review.googlesource.com/c/device/linaro/dragonboard/+/1774872
> >
> > Admittedly, it does take a short-cut. As your algorithm above,
> > digging up the devices and finding the sys/bus path to read the reg
> > value and pipe through hexdump (which android doesn't have) seemed
> > overly obtuse when the address is in the node name itself (while the
> > only way to be sure, one normally doesn't use spectroscopy to
> > determine the value of a coin when you can read what's printed on it
> > :). But, should the node naming be further changed at least the
> > infrastructure we have can be reworked fairly easily to adapt now.
> >
> > In any case, as we can handle the name change now, if you want to
> > resubmit your patch, we would no longer object (but can't promise no
> > one else might be bitten). Sorry for the delay this caused, and we
> > appreciate you working with us to find a solution.
>
> Great! Thanks for sending the notification. I'll resend the patch with a
> reference to your report and to the update made to AOSP, as soon as I
> am done with my current task.
>
Amit's change makes future versions of AOSP able to cope with changes in
the UDC name, unfortunately it doesn't change the fact that renaming the
node breaks compatibility in non-Android user space (or any existing
branches/tags of AOSP).
Regards,
Bjorn
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next prev parent reply other threads:[~2021-08-18 3:47 UTC|newest]
Thread overview: 109+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20201020115959.2658-1-Sergey.Semin@baikalelectronics.ru>
2020-10-20 11:59 ` [PATCH 01/29] usb: dwc3: Discard synopsys,dwc3 compatibility string Serge Semin
2020-10-20 12:15 ` [PATCH 01/29] usb: dwc3: Discard synopsys, dwc3 " Andy Shevchenko
2020-10-20 12:28 ` [PATCH 01/29] usb: dwc3: Discard synopsys,dwc3 " Krzysztof Kozlowski
2020-10-20 12:33 ` Serge Semin
2020-10-20 12:27 ` Felipe Balbi
2020-10-20 11:59 ` [PATCH 02/29] arm: dts: keystone: Correct DWC USB3 compatible string Serge Semin
2020-10-20 12:30 ` Krzysztof Kozlowski
2020-10-20 11:59 ` [PATCH 03/29] arm: dts: am437x: " Serge Semin
2020-10-20 12:31 ` Krzysztof Kozlowski
2020-11-10 13:17 ` Tony Lindgren
2020-10-20 11:59 ` [PATCH 04/29] arm: dts: exynos: " Serge Semin
2020-10-26 18:55 ` Krzysztof Kozlowski
2020-10-20 11:59 ` [PATCH 05/29] arm64: dts: amlogic: meson-g12: Set FL-adj property value Serge Semin
2020-10-20 12:34 ` Krzysztof Kozlowski
2020-10-20 12:44 ` Serge Semin
2020-10-20 12:46 ` Krzysztof Kozlowski
2020-10-20 13:06 ` Neil Armstrong
2020-10-20 19:38 ` Martin Blumenstingl
2020-10-20 11:59 ` [PATCH 06/29] arc: dts: Harmonize EHCI/OHCI DT nodes name Serge Semin
2020-10-20 12:35 ` Krzysztof Kozlowski
2020-10-20 11:59 ` [PATCH 07/29] arm: dts: bcm53x: " Serge Semin
2020-10-20 12:34 ` Krzysztof Kozlowski
2020-10-22 20:43 ` Florian Fainelli
2020-10-20 11:59 ` [PATCH 08/29] arm: dts: stm32: " Serge Semin
2020-10-20 12:36 ` Krzysztof Kozlowski
2020-11-09 10:43 ` Alexandre Torgue
2020-10-20 11:59 ` [PATCH 09/29] arm: dts: hisi-x5hd2: " Serge Semin
2020-10-20 12:36 ` Krzysztof Kozlowski
2020-10-20 11:59 ` [PATCH 10/29] arm: dts: lpc18xx: " Serge Semin
2020-10-20 12:37 ` Krzysztof Kozlowski
2020-10-21 19:02 ` Vladimir Zapolskiy
2020-10-20 11:59 ` [PATCH 11/29] arm64: dts: hisi: " Serge Semin
2020-10-20 12:37 ` Krzysztof Kozlowski
2020-10-20 11:59 ` [PATCH 12/29] mips: dts: jz47x: " Serge Semin
2020-10-20 12:40 ` Krzysztof Kozlowski
2020-10-20 11:59 ` [PATCH 13/29] mips: dts: sead3: " Serge Semin
2020-10-20 12:37 ` Krzysztof Kozlowski
2020-10-20 11:59 ` [PATCH 14/29] mips: dts: ralink: mt7628a: " Serge Semin
2020-10-20 12:38 ` Krzysztof Kozlowski
2020-10-20 11:59 ` [PATCH 15/29] powerpc: dts: akebono: " Serge Semin
2020-10-20 12:38 ` Krzysztof Kozlowski
2020-10-20 11:59 ` [PATCH 16/29] arm: dts: bcm5301x: Harmonize xHCI " Serge Semin
2020-10-20 12:38 ` Krzysztof Kozlowski
2020-10-22 20:44 ` Florian Fainelli
2020-10-20 11:59 ` [PATCH 17/29] arm64: dts: marvell: cp11x: " Serge Semin
2020-10-20 12:40 ` Krzysztof Kozlowski
2020-10-20 11:59 ` [PATCH 18/29] arm: dts: marvell: armada-375: Harmonize DWC USB3 " Serge Semin
2020-10-20 12:43 ` Krzysztof Kozlowski
2020-10-20 11:59 ` [PATCH 19/29] arm: dts: exynos: " Serge Semin
2020-10-26 18:56 ` Krzysztof Kozlowski
2020-10-20 11:59 ` [PATCH 20/29] arm: dts: keystone: " Serge Semin
2020-10-20 12:41 ` Krzysztof Kozlowski
2020-10-20 11:59 ` [PATCH 21/29] arm: dts: ls1021a: " Serge Semin
2020-10-20 12:46 ` Krzysztof Kozlowski
2020-11-01 7:37 ` Shawn Guo
2020-10-20 11:59 ` [PATCH 22/29] arm: dts: omap5: " Serge Semin
2020-10-20 12:41 ` Krzysztof Kozlowski
2020-11-10 13:18 ` Tony Lindgren
2020-10-20 11:59 ` [PATCH 23/29] arm: dts: stih407-family: " Serge Semin
2020-10-20 12:41 ` Krzysztof Kozlowski
2020-10-20 11:59 ` [PATCH 24/29] arm64: dts: allwinner: h6: " Serge Semin
2020-10-20 12:42 ` Krzysztof Kozlowski
2020-10-22 16:13 ` Maxime Ripard
2020-10-20 11:59 ` [PATCH 25/29] arm64: dts: apm: " Serge Semin
2020-10-20 12:42 ` Krzysztof Kozlowski
2020-10-20 11:59 ` [PATCH 26/29] arm64: dts: exynos: " Serge Semin
2020-10-20 12:43 ` Krzysztof Kozlowski
2020-10-22 11:25 ` Serge Semin
2020-10-26 18:57 ` Krzysztof Kozlowski
2020-10-20 11:59 ` [PATCH 27/29] arm64: dts: layerscape: " Serge Semin
2020-10-20 12:47 ` Krzysztof Kozlowski
2020-11-01 7:37 ` Shawn Guo
2020-10-20 11:59 ` [PATCH 28/29] arm64: dts: hi3660: " Serge Semin
2020-10-20 12:44 ` Krzysztof Kozlowski
2020-10-20 11:59 ` [PATCH 29/29] arm64: dts: qcom: " Serge Semin
2020-10-20 12:44 ` Krzysztof Kozlowski
2020-11-02 7:34 ` Jun Li
2020-11-03 23:23 ` Bjorn Andersson
2020-11-10 12:12 ` Serge Semin
2021-07-14 0:07 ` John Stultz
2021-07-14 2:27 ` Bjorn Andersson
2021-07-21 7:39 ` Greg Kroah-Hartman
2021-07-14 12:48 ` Serge Semin
2021-07-14 14:59 ` Bjorn Andersson
2021-07-21 7:38 ` Greg Kroah-Hartman
2021-07-21 10:02 ` Serge Semin
2021-07-21 10:29 ` Greg Kroah-Hartman
2021-07-21 10:45 ` Krzysztof Kozlowski
2021-07-21 11:02 ` Greg Kroah-Hartman
2021-07-21 11:10 ` Krzysztof Kozlowski
2021-07-21 11:25 ` Serge Semin
2021-07-21 18:08 ` John Stultz
2021-07-22 18:12 ` Serge Semin
2021-07-22 19:17 ` Bjorn Andersson
2021-07-22 20:09 ` John Stultz
2021-07-22 22:09 ` Serge Semin
2021-08-14 1:06 ` John Stultz
2021-08-15 19:46 ` Serge Semin
2021-08-18 3:44 ` Bjorn Andersson [this message]
2021-08-19 11:03 ` Serge Semin
2021-07-22 21:54 ` Serge Semin
2021-07-23 8:17 ` Greg Kroah-Hartman
2021-07-21 20:09 ` Bjorn Andersson
2021-07-23 8:18 ` Greg Kroah-Hartman
2021-07-23 14:34 ` Bjorn Andersson
2021-07-23 15:54 ` Greg Kroah-Hartman
2021-07-23 19:54 ` Bjorn Andersson
2021-07-24 7:50 ` Greg Kroah-Hartman
2021-07-21 7:37 ` Greg Kroah-Hartman
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