Re: [PATCH] vme: 8-bit status/id takes 256 values, not 255

[Martyn Welch]

On 18/10/15 18:07, Dmitry Kalinkin wrote:
> On Sun, Oct 18, 2015 at 9:30 AM, Martyn Welch <martyn@xxxxxxxxxxxx> wrote:
> > On 10 October 2015 at 23:00, Dmitry Kalinkin <dmitry.kalinkin@xxxxxxxxx> wrote:
> > > Fixes an off by one array size.
> > The Status/ID is an 8-bit value (OK, the standard states it can be a
> > 8, 16 or 32-bit value, however both of the chipsets we support at this
> > point in time support an 8-bit value), why do we need a 256th entry in
> > the array?
> Hi Martyn,
>
> 8 bit signal spans 256 values from 8'b0000_0000 to 8'b1111_1111.
> In order to serve that we need a C array of size 256.
> callback[255]; in the original code means that array has 255 elements
> with indices from 0 to 254, there would be no way to register callback
> for a valid Status/ID value of 255 (aka 8'b1111_1111). For that we
> need a 256th element.

Err, yep. (Curses self for being so stupid.)

Signed-off-by: Martyn Welch <martyn@xxxxxxxxxxxx>

> Dmitri
>
> > Martyn
> >
> > > Signed-off-by: Dmitry Kalinkin <dmitry.kalinkin@xxxxxxxxx>
> > > ---
> > >   drivers/vme/vme_bridge.h | 4 +++-
> > >   include/linux/vme.h      | 3 +++
> > >   2 files changed, 6 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/vme/vme_bridge.h b/drivers/vme/vme_bridge.h
> > > index 397578a..b59cbee 100644
> > > --- a/drivers/vme/vme_bridge.h
> > > +++ b/drivers/vme/vme_bridge.h
> > > @@ -1,6 +1,8 @@
> > >   #ifndef _VME_BRIDGE_H_
> > >   #define _VME_BRIDGE_H_
> > >
> > > +#include <linux/vme.h>
> > > +
> > >   #define VME_CRCSR_BUF_SIZE (508*1024)
> > >   /*
> > >    * Resource structures
> > > @@ -91,7 +93,7 @@ struct vme_callback {
> > >
> > >   struct vme_irq {
> > >          int count;
> > > -       struct vme_callback callback[255];
> > > +       struct vme_callback callback[VME_NUM_STATUSID];
> > >   };
> > >
> > >   /* Allow 16 characters for name (including null character) */
> > > diff --git a/include/linux/vme.h b/include/linux/vme.h
> > > index c013135..71e4a6d 100644
> > > --- a/include/linux/vme.h
> > > +++ b/include/linux/vme.h
> > > @@ -81,6 +81,9 @@ struct vme_resource {
> > >
> > >   extern struct bus_type vme_bus_type;
> > >
> > > +/* Number of VME interrupt vectors */
> > > +#define VME_NUM_STATUSID       256
> > > +
> > >   /* VME_MAX_BRIDGES comes from the type of vme_bus_numbers */
> > >   #define VME_MAX_BRIDGES                (sizeof(unsigned int)*8)
> > >   #define VME_MAX_SLOTS          32
> > > --
> > > 1.8.3.1

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