[PATCH xserver] randr: Do not check the screen size bound for gpu screens
Hans de Goede
hdegoede at redhat.com
Mon Jun 20 17:27:31 UTC 2016
Hi,
On 20-06-16 18:32, Nikhil Mahale wrote:
> Sorry for late reply, Hans. See inline -
>
> On 06/13/2016 10:36 PM, Hans de Goede wrote:
>> Hi,
>>
>> On 20-05-16 07:00, Nikhil Mahale wrote:
>>> For gpu screen, CrtcSet set/adjust the master screen size along
>>> mode in following callstack -
>>>
>>> ProcRRSetCrtcConfig()
>>> |
>>> -> RRCrtcSet()
>>> |
>>> -> rrCheckPixmapBounding()
>>> |
>>> -> pScrPriv->rrScreenSetSize()
>>>
>>> Checking screen size bound for gpus screen cause some configurations
>>> to fails, e.g
>>>
>>> $ xrandr --output eDP --mode 1920x1080 --pos 0x0 --output HDMI \
>>> --mode 2560x1440 --pos 0x0
>>>
>>> Here xrandr utility first sets screen size to 2560x1440 which
>>> gets resized to 1920x1080 on RRSetCrtcConfig request for eDP,
>>> and then RRSetCrtcConfig request for HDMI fails because
>>> of failure of screen bound check.
>>
>> Hmm, but one has the same problem when not using clone mode,
>> then the master screen size must be made big enough to hold
>> both crtc-s, so how come this has never been a problem then ?
>>
>> I've a feeling that in that case we end up doing things in
>> finer grained steps. What if you do:
>>
>> $ xrandr --output eDP --mode 1920x1080 --pos 0x0
>> $ xrandr --output HDMI --mode 2560x1440 --pos 0x0
>>
>> ? Does that work ? If that works, which I would expect it will,
>> then this should be fixed in the xrandr utility instead IMHO.
>>
>> Just circumventing the screen size check for slave outputs
>> seem to go against the xrandr-1.2 spec to me.
>>
>> Also I guess one can reproduce the same problem without using
>> slave-outputs, in which case your patch will not help.
>>
>
> I don't think we could reproduce this problem without using slave-
> output, because rrScreenSetSize() path which I explained in commit
> message is not there, isn't it?
>
> Let me try to explain differece between both sequence of commands,
> please correct me if required -
>
> $ xrandr --output eDP --mode 1920x1080 --pos 0x0 --output HDMI \
> --mode 2560x1440 --pos 0x0
>
> -----------------------------------------------------------------------
> | Cmd | Screen size | eDP | HDMI |
> -----------------------------------------------------------------------
> | RRSetScreenSize | 2560x1440 | - | - |
> -----------------------------------------------------------------------
> | RRSetCrtcConfig | 1920x1080 | 1920x1080 | - |
> | | changed from 2560x1440 | | |
> | | because of rrScreenSetSize() | | |
> | | path explained in commit | | |
> | | msg. ....(A) | | |
> -----------------------------------------------------------------------
> | RRSetCrtcConfig | 2560x1440 | 1920x1080 | failed |
> -----------------------------------------------------------------------
Ah I see now, this will only happen when the eDP is a slave output,
I was thinking that the HDMI would be a slave output, but that does
not matter, this problem will happen independ of the HDMI being a normal
or a slave output, as long as the eDP is a slave output.
> $ xrandr --output eDP --mode 1920x1080 --pos 0x0
> $ xrandr --output HDMI --mode 2560x1440 --pos 0x0
>
>
> ------------------------------------------------------------------------
> | Cmd | Screen size | eDP | HDMI |
> ------------------------------------------------------------------------
> | RRSetScreenSize | 1920x1080 | - | - |
> ------------------------------------------------------------------------
> | RRSetCrtcConfig | 1920x1080 | 1920x1080 | - |
> ------------------------------------------------------------------------
> | RRSetScreenSize | 2560x1440 | 1920x1080 | - |
> ------------------------------------------------------------------------
> | RRSetCrtcConfig | 2560x1440 | 1920x1080 | 2560x1440 |
> ------------------------------------------------------------------------
>
> Case (A) is not there in second sequence of xrand commands, so you could not reproduce problem.
Right, so you can get things to work without requiring a server change,
iow this may be considered a xrandr utility bug, it could reproduce the
sequence used in your second table, instead of skipping the second
RRSetScreenSize.
OTOH this may indeed be a server bug, but your fix is not the right
one, I wonder why we are doing a RRSetScreenSize for slave GPU-s at
all. Since we already check that the Screen is big enough in
ProcRRSetCrtcConfig?
I must admit that I'm not familiar enough with the code to answer
this myself, but the more I think about it the more your fix feels wrong,
because it will effectively lead to the following call sequence
equivalent:
> | RRSetScreenSize | 2560x1440 | - | - |
> ------------------------------------------------------------------------
> | rrSetScreenSize | 1920x1080 | - | - |
> ------------------------------------------------------------------------
> | RRSetCrtcConfig | 1920x1080 | 1920x1080 | - |
> ------------------------------------------------------------------------
> | rrSetScreenSize | 2560x1440 | 1920x1080 | - |
> ------------------------------------------------------------------------
> | RRSetCrtcConfig | 2560x1440 | 1920x1080 | 2560x1440 |
So we get 2 extra rrSetScreenSize calls leading to extra bonus flickering on
changing things.
Where as instead we want:
> | RRSetScreenSize | 2560x1440 | - | - |
> ------------------------------------------------------------------------
> | RRSetCrtcConfig | 1920x1080 | 1920x1080 | - |
> ------------------------------------------------------------------------
> | RRSetCrtcConfig | 2560x1440 | 1920x1080 | 2560x1440 |
As said I'm not familiar enough with all the subtleties of the randr
code to say that we can just skip calling rrCheckPixmapBounding() at all,
but we can change it to only ever enlarge the screen. That should be safe
to do, as I would expect the xrandr utility (*) to add an explicit
RRSetScreenSize at the end of configuration if the size needs to shrink.
IOW what if we do this:
--- a/randr/rrcrtc.c
+++ b/randr/rrcrtc.c
@@ -561,8 +561,8 @@ rrCheckPixmapBounding(ScreenPtr pScreen,
new_width = newsize->x2 - newsize->x1;
new_height = newsize->y2 - newsize->y1;
- if (new_width == screen_pixmap->drawable.width &&
- new_height == screen_pixmap->drawable.height) {
+ if (new_width <= screen_pixmap->drawable.width &&
+ new_height <= screen_pixmap->drawable.height) {
} else {
pScrPriv->rrScreenSetSize(pScreen, new_width, new_height, 0, 0);
}
That would actually save us 2 pScrPriv->rrScreenSetSize() calls, so
that seems like a better fix to me.
Dave or Ajax do you have any input on this ?
Regards,
Hans
*) And equivalent gui control-panel applets
>
> Thanks,
> Nikhil Mahale
>
>>
>> Regards,
>>
>> Hans
>>
>>
>>>
>>> Signed-off-by: Nikhil Mahale <nmahale at nvidia.com>
>>> ---
>>> randr/rrcrtc.c | 19 ++++++-------------
>>> 1 file changed, 6 insertions(+), 13 deletions(-)
>>>
>>> diff --git a/randr/rrcrtc.c b/randr/rrcrtc.c
>>> index 566a3db..82db9a8 100644
>>> --- a/randr/rrcrtc.c
>>> +++ b/randr/rrcrtc.c
>>> @@ -1176,27 +1176,20 @@ ProcRRSetCrtcConfig(ClientPtr client)
>>>
>>> #ifdef RANDR_12_INTERFACE
>>> /*
>>> + * For gpu screen, CrtcSet set/adjust the master screen size
>>> along
>>> + * with mode.
>>> + *
>>> * Check screen size bounds if the DDX provides a 1.2 interface
>>> * for setting screen size. Else, assume the CrtcSet sets
>>> * the size along with the mode. If the driver supports
>>> transforms,
>>> * then it must allow crtcs to display a subset of the
>>> screen, so
>>> * only do this check for drivers without transform support.
>>> */
>>> - if (pScrPriv->rrScreenSetSize && !crtc->transforms) {
>>> + if (!pScreen->isGPU && pScrPriv->rrScreenSetSize &&
>>> !crtc->transforms) {
>>> int source_width;
>>> int source_height;
>>> PictTransform transform;
>>> struct pixman_f_transform f_transform, f_inverse;
>>> - int width, height;
>>> -
>>> - if (pScreen->isGPU) {
>>> - width = pScreen->current_master->width;
>>> - height = pScreen->current_master->height;
>>> - }
>>> - else {
>>> - width = pScreen->width;
>>> - height = pScreen->height;
>>> - }
>>>
>>> RRTransformCompute(stuff->x, stuff->y,
>>> mode->mode.width, mode->mode.height,
>>> @@ -1206,13 +1199,13 @@ ProcRRSetCrtcConfig(ClientPtr client)
>>>
>>> RRModeGetScanoutSize(mode, &transform, &source_width,
>>> &source_height);
>>> - if (stuff->x + source_width > width) {
>>> + if (stuff->x + source_width > pScreen->width) {
>>> client->errorValue = stuff->x;
>>> free(outputs);
>>> return BadValue;
>>> }
>>>
>>> - if (stuff->y + source_height > height) {
>>> + if (stuff->y + source_height > pScreen->height) {
>>> client->errorValue = stuff->y;
>>> free(outputs);
>>> return BadValue;
>>>
>> _______________________________________________
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