staging: comedi: simplify returned errors for comedi_read()
authorIan Abbott <abbotti@mev.co.uk>
Mon, 12 Oct 2015 16:21:28 +0000 (17:21 +0100)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Tue, 13 Oct 2015 17:29:48 +0000 (10:29 -0700)
commit39582847757ef79fb9de2661dd9297f1c988478d
treef91b4242a549bb4a24cbf3b795c536cd9e04be4b
parenta8ed75c0836ebc530f7fbf613bba75de3656b105
staging: comedi: simplify returned errors for comedi_read()

In order to perform a "read" file operation, an asynchronous COMEDI
command in the "read" direction needs to have been set up by the current
file object on the COMEDI "read" subdevice associated with the file
object.  If there is a "read" subdevice, but a command has not been set
up by the file object (or is has been set-up in the wrong direction),
`comedi_read()` currently returns one of two error values `-EINVAL` or
`-EACCES`.  `-EACCES` is returned if the command was set up by a
different subdevice, or somewhat randomly, if a COMEDI "instruction" is
currently being processed.  `-EINVAL` is returned in other cases.
Simplify it by returning `-EINVAL` for all these cases.

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