v4l2: api: Fix ioctl() argument type mismatch. #34
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Annoyingly, the libc crate defines ioctl()'s argument types differently on different platforms. On x86_64-unknown-linux-gnu, the existing code works just fine. But, on aarch64-unknown-linux-musl (and Android apparently), the libc crate instead says it takes an int, so we get a compilation error. We could work around this by writing the code differently for different targets with #[cfg()]. But, that's less than ideal. So, hack around this by using syscall() instead. It's a variadic function, so we can just pass ~whatever~ into it. We're kind of depending on C's type conversion rules by doing so, but this turns out to be kind of how e.g. glibc does it anyway. At the end of the day: this should "just work" on all targets. Signed-off-by: Axel Rasmussen <axelrasmussen@google.com>
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LGTM; thanks for adding the inline comment! |
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Annoyingly, the libc crate defines ioctl()'s argument types differently
on different platforms. On x86_64-unknown-linux-gnu, the existing code
works just fine. But, on aarch64-unknown-linux-musl (and Android
apparently), the libc crate instead says it takes an int, so we get a
compilation error.
We could work around this by writing the code differently for different
targets with #[cfg()]. But, that's less than ideal.
So, hack around this by using syscall() instead. It's a variadic
function, so we can just pass
whateverinto it. We're kind ofdepending on C's type conversion rules by doing so, but this turns out
to be kind of how e.g. glibc does it anyway.
At the end of the day: this should "just work" on all targets.
Signed-off-by: Axel Rasmussen axelrasmussen@google.com