Re: [PATCH 1/2] xen/displif: Protocol version 2

[Jürgen Groß <jgross@xxxxxxxx>]

On 30.06.20 09:09, Oleksandr Andrushchenko wrote:
> On 6/30/20 10:03 AM, Jürgen Groß wrote:
> > On 30.06.20 08:13, Oleksandr Andrushchenko wrote:
> > > On 6/29/20 10:02 AM, Jürgen Groß wrote:
> > > > On 20.05.20 11:04, Oleksandr Andrushchenko wrote:
> > > > > From: Oleksandr Andrushchenko <oleksandr_andrushchenko@xxxxxxxx>
> > > > >
> > > > > 1. Change protocol version from string to integer
> > > > >
> > > > > Version string, which is in fact an integer, is hard to handle in the
> > > > > code that supports different protocol versions. To simplify that
> > > > > make the version an integer.
> > > > >
> > > > > 2. Pass buffer offset with XENDISPL_OP_DBUF_CREATE
> > > > >
> > > > > There are cases when display data buffer is created with non-zero
> > > > > offset to the data start. Handle such cases and provide that offset
> > > > > while creating a display buffer.
> > > > >
> > > > > 3. Add XENDISPL_OP_GET_EDID command
> > > > >
> > > > > Add an optional request for reading Extended Display Identification
> > > > > Data (EDID) structure which allows better configuration of the
> > > > > display connectors over the configuration set in XenStore.
> > > > > With this change connectors may have multiple resolutions defined
> > > > > with respect to detailed timing definitions and additional properties
> > > > > normally provided by displays.
> > > > >
> > > > > If this request is not supported by the backend then visible area
> > > > > is defined by the relevant XenStore's "resolution" property.
> > > > >
> > > > > If backend provides extended display identification data (EDID) with
> > > > > XENDISPL_OP_GET_EDID request then EDID values must take precedence
> > > > > over the resolutions defined in XenStore.
> > > > >
> > > > > 4. Bump protocol version to 2.
> > > > >
> > > > > Signed-off-by: Oleksandr Andrushchenko 
> > > > > <oleksandr_andrushchenko@xxxxxxxx>
> > > > > ---
> > > > >    xen/include/public/io/displif.h | 83 
> > > > > +++++++++++++++++++++++++++++++--
> > > > >    1 file changed, 80 insertions(+), 3 deletions(-)
> > > > >
> > > > > diff --git a/xen/include/public/io/displif.h 
> > > > > b/xen/include/public/io/displif.h
> > > > > index cc5de9cb1f35..4d43ba5078c8 100644
> > > > > --- a/xen/include/public/io/displif.h
> > > > > +++ b/xen/include/public/io/displif.h
> > > > > @@ -38,7 +38,7 @@
> > > > >     *                           Protocol version
> > > > > ****************************************************************************** 
> > > > >
> > > > >     */
> > > > > -#define XENDISPL_PROTOCOL_VERSION     "1"
> > > > > +#define XENDISPL_PROTOCOL_VERSION     2
> > > > This is not very nice regarding compatibility.
> > > >
> > > > Can't you add a new macro for the integer value?
> > > We can leave it as is, e.g. define XENDISPL_PROTOCOL_VERSION as "2",
> > >
> > > so we do not break the existing users. Then if every user of the 
> > > header has
> > > its local copy (this is what we now use in the display backend), then 
> > > that
> > > local copy can be changed in a way suitable for the concrete user, 
> > > e.g. "2"
> > > redefined to 2. This cannot be done (?) for the Linux Kernel though.
> > >
> > > Or we can have
> > >
> > > #define XENDISPL_PROTOCOL_VERSION     "2"
> > >
> > > #define XENDISPL_PROTOCOL_VERSION_INT  2
> > >
> > > Jurgen, what's your preference here?
> > I would prefer the latter, as it avoids the need to modify the header
> > when copying it to a local project.
> Ok, I'll have 2 definitions then
>
> Anything else (beside the comments on new functionality) I can add/change
>
> before sending v2 of the patch?
I would have said so. :-)


Juergen