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

["Jürgen Groß" <jgross@suse.com>]

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@epam.com>
>>>>>
>>>>> 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@epam.com>
>>>>> ---
>>>>>    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