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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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