staging: comedi: return error on "read" if no command set up
authorIan Abbott <abbotti@mev.co.uk>
Mon, 12 Oct 2015 16:21:27 +0000 (17:21 +0100)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Tue, 13 Oct 2015 17:29:48 +0000 (10:29 -0700)
commita8ed75c0836ebc530f7fbf613bba75de3656b105
treee790c2e7376c4303a5e5a7b21deb0bb28520c6f0
parentf84e27adfc4cb0c4aa97d830c43f8c82aca0547c
staging: comedi: return error on "read" if no command set up

The "read" file operation handler, `comedi_read()` returns an error for
pretty much any condition that prevents a "read" going ahead.  One of
the conditions that prevents a "read" going ahead is that no
asynchronous command has been set up, but that currently results in a
return value of 0 (unless COMEDI instructions are being processed or an
asynchronous command has been set up by a different file object).
Change it to return `-EINVAL` in this case.

Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Reviewed-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
drivers/staging/comedi/comedi_fops.c