linux-kernel - Re: [PATCH v2] rpmsg: core: Add wildcard match for name service

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Date:   Thu, 26 Mar 2020 14:21:51 -0600
From:   Mathieu Poirier <mathieu.poirier@...aro.org>
To:     Suman Anna <s-anna@...com>
Cc:     Ohad Ben-Cohen <ohad@...ery.com>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        linux-remoteproc <linux-remoteproc@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] rpmsg: core: Add wildcard match for name service

On Thu, 26 Mar 2020 at 09:06, Suman Anna <s-anna@...com> wrote:
>
> Hi Mathieu,
>
> On 3/10/20 10:50 AM, Mathieu Poirier wrote:
> > Adding the capability to supplement the base definition published
> > by an rpmsg_driver with a postfix description so that it is possible
> > for several entity to use the same service.
> >
> > Signed-off-by: Mathieu Poirier <mathieu.poirier@...aro.org>
> > Acked-by: Arnaud Pouliquen <arnaud.pouliquen@...com>
>
> So, the concern I have here is that we are retrofitting this into the
> existing 32-byte name field, and the question is if it is going to be
> enough in general. That's the reason I went with the additional 32-byte
> field with the "rpmsg: add a description field" patch.
>

That's a valid concern.

Did you consider increasing the size of RPMSG_NAME_SIZE to 64? Have
you found cases where that wouldn't work?  I did a survey of all the
places the #define is used and all destination buffers are also using
the same #define in their definition.  It would also be backward
compatible with firmware implementations that use 32 byte.

Thanks,
Mathieu

> regards
> Suman
>
> > ---
> > Changes for V2:
> > - Added Arnaud's Acked-by.
> > - Rebased to latest rproc-next.
> >
> >  drivers/rpmsg/rpmsg_core.c | 20 +++++++++++++++++++-
> >  1 file changed, 19 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/rpmsg/rpmsg_core.c b/drivers/rpmsg/rpmsg_core.c
> > index e330ec4dfc33..bfd25978fa35 100644
> > --- a/drivers/rpmsg/rpmsg_core.c
> > +++ b/drivers/rpmsg/rpmsg_core.c
> > @@ -399,7 +399,25 @@ ATTRIBUTE_GROUPS(rpmsg_dev);
> >  static inline int rpmsg_id_match(const struct rpmsg_device *rpdev,
> >                                 const struct rpmsg_device_id *id)
> >  {
> > -     return strncmp(id->name, rpdev->id.name, RPMSG_NAME_SIZE) == 0;
> > +     size_t len = min_t(size_t, strlen(id->name), RPMSG_NAME_SIZE);
> > +
> > +     /*
> > +      * Allow for wildcard matches.  For example if rpmsg_driver::id_table
> > +      * is:
> > +      *
> > +      * static struct rpmsg_device_id rpmsg_driver_sample_id_table[] = {
> > +      *      { .name = "rpmsg-client-sample" },
> > +      *      { },
> > +      * }
> > +      *
> > +      * Then it is possible to support "rpmsg-client-sample*", i.e:
> > +      *      rpmsg-client-sample
> > +      *      rpmsg-client-sample_instance0
> > +      *      rpmsg-client-sample_instance1
> > +      *      ...
> > +      *      rpmsg-client-sample_instanceX
> > +      */
> > +     return strncmp(id->name, rpdev->id.name, len) == 0;
> >  }
> >
> >  /* match rpmsg channel and rpmsg driver */
> >
>