Re: [Xen-devel] [PATCH 1/2] xen, input: add xen-kbdfront module parameter for setting resolution

[Oleksandr Andrushchenko]

On 04/10/2017 04:50 PM, Juergen Gross wrote:
> On 10/04/17 15:44, Oleksandr Andrushchenko wrote:
> > Hi, Juergen!
> >
> > On 03/21/2017 07:19 PM, Juergen Gross wrote:
> > > Add a parameter for setting the resolution of xen-kbdfront in order to
> > > be able to cope with a (virtual) frame buffer of arbitrary resolution.
> > >
> > > Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
> > > ---
> > >    drivers/input/misc/xen-kbdfront.c | 10 ++++++++--
> > >    1 file changed, 8 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/drivers/input/misc/xen-kbdfront.c
> > > b/drivers/input/misc/xen-kbdfront.c
> > > index 3900875..2df5678 100644
> > > --- a/drivers/input/misc/xen-kbdfront.c
> > > +++ b/drivers/input/misc/xen-kbdfront.c
> > > @@ -41,6 +41,12 @@ struct xenkbd_info {
> > >        char phys[32];
> > >    };
> > >    +enum { KPARAM_WIDTH, KPARAM_HEIGHT, KPARAM_CNT };
> > > +static int size[KPARAM_CNT] = { XENFB_WIDTH, XENFB_HEIGHT };
> > > +module_param_array(size, int, NULL, 0444);
> > is this by intention that you use 0444 here?
> > It means read-only, thus one cannot change these,
> > so what is the point of the module parameters then?
> You can see the settings in sysfs.
this is good so we can see actual width/height
used by the pv driver
> The values are settable via boot parameter.
but then, if one has other values set in XenStore,
these will/may be overridden, making it inconsistent,
e.g. values loaded at start as module parameters
(*size* array) is not going to be updated on
XenbusStateInitWait/XenbusStateConnected. So, we'll
end up with wrong parameters shown via sysfs
one more question is why do we need module parameters
if the same can be read from XenStore?

> Juergen
Thank you,
Oleksandr