From a8ed75c0836ebc530f7fbf613bba75de3656b105 Mon Sep 17 00:00:00 2001 From: Ian Abbott Date: Mon, 12 Oct 2015 17:21:27 +0100 Subject: [PATCH] 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 Reviewed-by: H Hartley Sweeten Signed-off-by: Greg Kroah-Hartman --- drivers/staging/comedi/comedi_fops.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/drivers/staging/comedi/comedi_fops.c b/drivers/staging/comedi/comedi_fops.c index 88ba0b648805..190592ad0921 100644 --- a/drivers/staging/comedi/comedi_fops.c +++ b/drivers/staging/comedi/comedi_fops.c @@ -2478,8 +2478,12 @@ static ssize_t comedi_read(struct file *file, char __user *buf, size_t nbytes, } async = s->async; - if (!s->busy || !nbytes) + if (!nbytes) + goto out; + if (!s->busy) { + retval = -EINVAL; goto out; + } if (s->busy != file) { retval = -EACCES; goto out; @@ -2517,6 +2521,7 @@ static ssize_t comedi_read(struct file *file, char __user *buf, size_t nbytes, break; } if (!s->busy) { + retval = -EINVAL; break; } if (s->busy != file) { -- 2.20.1