[igt-dev] [PATCH i-g-t 1/5] igt/kms_getfb: Check the iface exists before use

[Chris Wilson]

Quoting Antonio Argenziano (2018-10-01 19:36:24)
> 
> 
> On 28/09/18 03:19, Chris Wilson wrote:
> > If the driver doesn't support the getfb iface (e.g. because KMS has been
> > disabled), the ioctls will fail with ENOTSUP. This is expected, so skip
> > the test as nothing useful can be learnt.
> > 
> > Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> > ---
> >   tests/kms_getfb.c | 40 ++++++++++++++++++++++++++++++++++++++--
> >   1 file changed, 38 insertions(+), 2 deletions(-)
> > 
> > diff --git a/tests/kms_getfb.c b/tests/kms_getfb.c
> > index 81d796a42..71d65488f 100644
> > --- a/tests/kms_getfb.c
> > +++ b/tests/kms_getfb.c
> > @@ -40,6 +40,40 @@
> >   #include "drm.h"
> >   #include "drm_fourcc.h"
> >   
> > +static bool has_getfb_iface(int fd)
> > +{
> > +     struct drm_mode_fb_cmd arg = { };
> > +     int err;
> > +
> > +     err = 0;
> > +     if (drmIoctl(fd, DRM_IOCTL_MODE_GETFB, &arg))
> > +             err = -errno;
> > +     switch (err) {
> > +     case -ENOTTY: /* ioctl unrecognised (kernel too old) */
> > +     case -ENOTSUP: /* driver doesn't support KMS */
> > +             return false;
> > +     default:
> > +             return true;
> > +     }
> > +}
> > +
> > +static bool has_addfb2_iface(int fd)
> > +{
> > +     struct drm_mode_fb_cmd2 arg = { };
> > +     int err;
> > +
> > +     err = 0;
> > +     if (drmIoctl(fd, DRM_IOCTL_MODE_ADDFB2, &arg) == 0)
> > +             err = -errno;
> 
> Shouldn't this^ be != 0?

Yup.
 
> > +     switch (err) {
> > +     case -ENOTTY: /* ioctl unrecognised (kernel too old) */
> > +     case -ENOTSUP: /* driver doesn't support KMS */
> > +             return false;
> > +     default:
> > +             return true;
> 
> Shouldn't we fail on every errno?

No. We want to be very careful in only fail at this point for errno we
know imply the interface is not supported so that we do not confuse an
illegal addfb2 request and fail later in the actual test.
-Chris