iio: buffer: return 0 for buffer getfd ioctl handler

As Lars pointed out, we could either return the FD vs memcpy-ing it to the
userspace data object.

However, this comment exposed a bug. We should return 0 or negative from
these ioctl() handlers. Because an ioctl() handler can also return
IIO_IOCTL_UNHANDLED (which is positive 1), which means that the ioctl()
handler doesn't support this ioctl number. Positive 1 could also be a valid
FD number in some corner cases.

The reason we did this is to be able to differentiate between an error
code and an unsupported ioctl number; for unsupported ioctl numbers, the
main loop should keep going.

Maybe we should change this to a higher negative number, to avoid such
cases when/if we add more ioctl() handlers.

Cc: Lars-Peter Clausen <[email protected]>
Fixes: f73f7f4da5818 ("iio: buffer: add ioctl() to support opening extra buffers for IIO device")
Signed-off-by: Alexandru Ardelean <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jonathan Cameron <[email protected]>

0 files changed, 0 insertions, 0 deletions