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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@pacbell.net>.
Signed-off-by: Marcin Slusarz <marcin.slusarz@gmail.com>
Cc: David Brownell <david-b@pacbell.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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