linux-kernel - [PATCH] usb/usbtest: comment on why this code "expects" negative and positive errnos

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Message-ID: <20080512181721.GA6031@joi>
Date:	Mon, 12 May 2008 20:17:25 +0200
From:	Marcin Slusarz <marcin.slusarz@...il.com>
To:	David Brownell <david-b@...bell.net>,
	LKML <linux-kernel@...r.kernel.org>
Cc:	Greg Kroah-Hartman <gregkh@...e.de>, linux-usb@...r.kernel.org
Subject: [PATCH] usb/usbtest: comment on why this code "expects" negative
	and positive errnos

On Mon, May 12, 2008 at 01:02:22AM -0700, David Brownell wrote:
> On Sunday 11 May 2008, Marcin Slusarz wrote:
> > 
> > test_ctrl_queue expects (?) positive and negative errnos.
> > what is going on here?
> 
> The sign is just a way to flag something:
> 
>                 /* some faults are allowed, not required */
> 
> The negative ones are required.  Positive codes are optional,
> in the sense that, depending on how the peripheral happens
> to be implemented, they won't necessarily be triggered.
> 
> For example, the test to fetch a device qualifier desriptor
> must succeed if the device is running at high speed.  So that
> test is marked as negative.  But when it's full speed, it
> could legitimately fail; marked as positive.  And so on for
> other tests.
> 
> Look at how the codes are *interpreted* to see it work.

Thanks for a response!
Lets document it.

---
Based on comment from David Brownell <david-b@...bell.net>.

Signed-off-by: Marcin Slusarz <marcin.slusarz@...il.com>
Cc: David Brownell <david-b@...bell.net>
---
 drivers/usb/misc/usbtest.c |    5 +++++
 1 files changed, 5 insertions(+), 0 deletions(-)

diff --git a/drivers/usb/misc/usbtest.c b/drivers/usb/misc/usbtest.c
index 742be3c..054dedd 100644
--- a/drivers/usb/misc/usbtest.c
+++ b/drivers/usb/misc/usbtest.c
@@ -856,6 +856,11 @@ test_ctrl_queue (struct usbtest_dev *dev, struct usbtest_param *param)
 		struct urb		*u;
 		struct usb_ctrlrequest	req;
 		struct subcase		*reqp;
+
+		/* sign of this variable means:
+		 *  -: tested code must return this (negative) error code
+		 *  +: tested code may return this (negative too) error code
+		 */
 		int			expected = 0;
 
 		/* requests here are mostly expected to succeed on any
-- 
1.5.4.5
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