Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933448AbbKRRzu (ORCPT ); Wed, 18 Nov 2015 12:55:50 -0500 Received: from smtp113.iad3a.emailsrvr.com ([173.203.187.113]:47559 "EHLO smtp113.iad3a.emailsrvr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755184AbbKRRzb (ORCPT ); Wed, 18 Nov 2015 12:55:31 -0500 X-Auth-ID: abbotti@mev.co.uk X-Sender-Id: abbotti@mev.co.uk From: Ian Abbott To: driverdev-devel@linuxdriverproject.org Cc: Greg Kroah-Hartman , Ian Abbott , H Hartley Sweeten , linux-kernel@vger.kernel.org Subject: [PATCH 8/8] staging: comedi: check for more errors for zero-length write Date: Wed, 18 Nov 2015 17:55:11 +0000 Message-Id: <1447869311-21955-9-git-send-email-abbotti@mev.co.uk> X-Mailer: git-send-email 2.6.2 In-Reply-To: <1447869311-21955-1-git-send-email-abbotti@mev.co.uk> References: <1447869311-21955-1-git-send-email-abbotti@mev.co.uk> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1911 Lines: 51 If the "write" file operation handler, `comedi_write()` is passed 0 for the amount to write, some error conditions are currently skipped and the function just returns 0. Change it to check those error conditions and return an error value if appropriate. The trickiest case is the check for when the previously set up asynchronous command has terminated with an error. In that case, `-EPIPE` is returned (as it is for a write of non-zero length) and the subdevice gets marked as non-busy. A zero-length write that returns 0 has no other effects, in particular, it does not cause the subdevice to be marked as non-busy. Signed-off-by: Ian Abbott --- drivers/staging/comedi/comedi_fops.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/drivers/staging/comedi/comedi_fops.c b/drivers/staging/comedi/comedi_fops.c index 5a9c9d9..d57fade 100644 --- a/drivers/staging/comedi/comedi_fops.c +++ b/drivers/staging/comedi/comedi_fops.c @@ -2331,8 +2331,6 @@ static ssize_t comedi_write(struct file *file, const char __user *buf, } async = s->async; - if (!nbytes) - goto out; if (s->busy != file || !(async->cmd.flags & CMDF_WRITE)) { retval = -EINVAL; goto out; @@ -2349,9 +2347,12 @@ static ssize_t comedi_write(struct file *file, const char __user *buf, if (!comedi_is_runflags_running(runflags)) { if (comedi_is_runflags_in_error(runflags)) retval = -EPIPE; - become_nonbusy = true; + if (retval || nbytes) + become_nonbusy = true; break; } + if (nbytes == 0) + break; /* Allocate all free buffer space. */ comedi_buf_write_alloc(s, async->prealloc_bufsz); -- 2.6.2 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/