linux-kernel - staging: comedi: COMEDI_BUFINFO: some behavioural changes

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Message-Id: <1455898437-4640-1-git-send-email-abbotti@mev.co.uk>
Date:	Fri, 19 Feb 2016 16:13:49 +0000
From:	Ian Abbott <abbotti@....co.uk>
To:	devel@...verdev.osuosl.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Ian Abbott <abbotti@....co.uk>,
	H Hartley Sweeten <hsweeten@...ionengravers.com>,
	linux-kernel@...r.kernel.org
Subject: staging: comedi: COMEDI_BUFINFO: some behavioural changes

These patches change the behavior of the `COMEDI_BUFINFO` ioctl, which
is used to manage buffer positions for a previously set up asynchronous
acquisition command.  It is used instead of the read and write file
operations when the buffer has been mmapped.

Patches 1 to 4 are fairly innocuous.  Patches 5 to 8 change the error
handling when the asynchronous command is no longer running, allow the
subdevice to become "non-busy" automatically in more cases (causing
subsequent calls to return `-EINVAL`), and report abnormal command
termination with return value `-EPIPE` (which also makes the subdevice
become non-busy).

1) staging: comedi: COMEDI_BUFINFO: get amount freed, not amount
   allocated
2) staging: comedi: COMEDI_BUFINFO: force bytes_read or bytes_written to
   0
3) staging: comedi: COMEDI_BUFINFO: update buffer before becoming
   non-busy
4) staging: comedi: COMEDI_BUFINFO: force bytes_written to 0 if stopped
5) staging: comedi: COMEDI_BUFINFO: return error if no active command
6) staging: comedi: COMEDI_BUFINFO: become non-busy even if bytes_read
   is 0
7) staging: comedi: COMEDI_BUFINFO: return -EPIPE for abnormal read
8) staging: comedi: COMEDI_BUFINFO: terminate "write" command when
   stopped

 drivers/staging/comedi/comedi_fops.c | 84 +++++++++++++++++++-----------------
 1 file changed, 44 insertions(+), 40 deletions(-)