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x/exp/io/spi: SPI on mipsle uses wrong IOCTL #26026

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svenschwermer opened this issue Jun 23, 2018 · 5 comments
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x/exp/io/spi: SPI on mipsle uses wrong IOCTL #26026

svenschwermer opened this issue Jun 23, 2018 · 5 comments
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FrozenDueToAge NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one.
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@svenschwermer
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What version of Go are you using (go version)?

go version go1.10.3 darwin/amd64

Does this issue reproduce with the latest release?

yes

What operating system and processor architecture are you using (go env)?

GOARCH="mipsle"
GOBIN=""
GOCACHE="/Users/sven/Library/Caches/go-build"
GOEXE=""
GOHOSTARCH="amd64"
GOHOSTOS="darwin"
GOOS="linux"
GOPATH="/Users/sven/go"
GORACE=""
GOROOT="/usr/local/Cellar/go/1.10.3/libexec"
GOTMPDIR=""
GOTOOLDIR="/usr/local/Cellar/go/1.10.3/libexec/pkg/tool/darwin_amd64"
GCCGO="gccgo"
GOMIPS="softfloat"
CC="clang"
CXX="clang++"
CGO_ENABLED="0"
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -mabi=32 -march=mips32 -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/var/folders/_j/ly_hzzjx5vjd2qbzd8qd2bch0000gn/T/go-build245470376=/tmp/go-build -gno-record-gcc-switches"

What did you do?

I used golang.org/x/exp/io/spi to write to an SPI device on a MIPS (32 bit, little endian) target.

The IOCTL used for writing the data (in spi.(*devfsConn).Tx) is wrong. The returned error message is inappropriate ioctl for device. strace prints ioctl(3, _IOC(_IOC_READ, 0x6b, 0, 0x20), 0x8c33efc) = -1 ENOTTY (Not a tty) instead of ioctl(3, SPI_IOC_MESSAGE(32), 0x8933f20) = 2.

If I'm not mistaken, the IOCTLs are offset on MIPS targets. See https://github.com/torvalds/linux/blob/master/arch/mips/include/uapi/asm/ioctl.h and https://github.com/torvalds/linux/blob/master/include/uapi/asm-generic/ioctl.h#L32
@ALTree ALTree changed the title SPI on mipsle uses wrong IOCTL x/exp/io/spi: SPI on mipsle uses wrong IOCTL Jun 23, 2018
@gopherbot gopherbot added this to the Unreleased milestone Jun 23, 2018
@ALTree ALTree added the NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one. label Jun 23, 2018
@ianlancetaylor
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CC @rakyll

@svenschwermer
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Here is a proposal for a fix: svenschwermer/golang.org-x-exp@8026287
This should also fix #16551.

@rakyll
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rakyll commented Jul 9, 2018

/cc @maruel

@maruel
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maruel commented Jul 23, 2018

Thanks. I filed google/periph#263 to correctly handle this in periph.io.

We don't plan to modify exp/io anymore.

@maruel maruel mentioned this issue Dec 21, 2018
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@ALTree
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ALTree commented Sep 7, 2020

Since x/exp/io is no longer developed and essentially frozen, I'm closing this issue.

@ALTree ALTree closed this as completed Sep 7, 2020
@golang golang locked and limited conversation to collaborators Sep 7, 2021
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@maruel @rakyll @ianlancetaylor @ALTree @svenschwermer @gopherbot