Re: [PATCH] usb: video: fix descriptor structures macros

[Sylvain Pelissier <sylvain.pelissier@gmail.com>]

On Thu, 28 Jan 2021 at 18:17, Sylvain Pelissier
<sylvain.pelissier@gmail.com> wrote:
>
> On Thu, 28 Jan 2021 at 09:22, Greg KH <gregkh@linuxfoundation.org> wrote:
> >
> > On Thu, Jan 28, 2021 at 09:12:59AM +0100, Sylvain Pelissier wrote:
> > > The macros defining structures for descriptors use token
> > > pasting incorrectly. For example, the macro
> > > UVC_EXTENSION_UNIT_DESCRIPTOR(1, 2) defines a structure named
> > > uvc_extension_unit_descriptor_p_2 which should be
> > > uvc_extension_unit_descriptor_1_2 instead.
> > >
> > > Signed-off-by: Sylvain Pelissier <sylvain.pelissier@gmail.com>
> > > ---
> > >  include/uapi/linux/usb/video.h | 6 +++---
> > >  1 file changed, 3 insertions(+), 3 deletions(-)
> > >
> > > diff --git a/include/uapi/linux/usb/video.h b/include/uapi/linux/usb/video.h
> > > index d854cb19c42c..1eb982df87a0 100644
> > > --- a/include/uapi/linux/usb/video.h
> > > +++ b/include/uapi/linux/usb/video.h
> > > @@ -324,7 +324,7 @@ struct uvc_extension_unit_descriptor {
> > >  #define UVC_DT_EXTENSION_UNIT_SIZE(p, n)             (24+(p)+(n))
> > >
> > >  #define UVC_EXTENSION_UNIT_DESCRIPTOR(p, n) \
> > > -     uvc_extension_unit_descriptor_##p_##n
> > > +     uvc_extension_unit_descriptor_##p##_##n
> > >
> > >  #define DECLARE_UVC_EXTENSION_UNIT_DESCRIPTOR(p, n)  \
> > >  struct UVC_EXTENSION_UNIT_DESCRIPTOR(p, n) {         \
> > > @@ -371,7 +371,7 @@ struct uvc_input_header_descriptor {
> > >  #define UVC_DT_INPUT_HEADER_SIZE(n, p)                       (13+(n*p))
> > >
> > >  #define UVC_INPUT_HEADER_DESCRIPTOR(n, p) \
> > > -     uvc_input_header_descriptor_##n_##p
> > > +     uvc_input_header_descriptor_##n##_##p
> > >
> > >  #define DECLARE_UVC_INPUT_HEADER_DESCRIPTOR(n, p)    \
> > >  struct UVC_INPUT_HEADER_DESCRIPTOR(n, p) {           \
> > > @@ -406,7 +406,7 @@ struct uvc_output_header_descriptor {
> > >  #define UVC_DT_OUTPUT_HEADER_SIZE(n, p)                      (9+(n*p))
> > >
> > >  #define UVC_OUTPUT_HEADER_DESCRIPTOR(n, p) \
> > > -     uvc_output_header_descriptor_##n_##p
> > > +     uvc_output_header_descriptor_##n##_##p
> > >
> > >  #define DECLARE_UVC_OUTPUT_HEADER_DESCRIPTOR(n, p)   \
> > >  struct UVC_OUTPUT_HEADER_DESCRIPTOR(n, p) {          \
> > > --
> > > 2.25.1
> > >
> >
> > And no one noticed this?  If not, then why do we have these defines at
> > all, as obviously they are not used :)
>
> The problem is not detected if you have descriptors with the second
> argument different each time since the structure name will change. It
> is maybe why it was not noticed. Nevertheless, the extension unit, the
> input header and the output header descriptors are part of the USB
> video class specification and are often used by devices. We have
> detected the problem while implementing a usb gadget having such
> descriptors.
>
Hi,
Do I need to change something for this patch ?
Thanks,

Sylvain
> >
> > thanks,
> >
> > greg k-h