Re: [PATCH v2 10/11] drm/qxl: rework cursor plane

From: Thomas Zimmermann <tzimmermann@suse.de>
To: Gerd Hoffmann <kraxel@redhat.com>
Cc: David Airlie <airlied@linux.ie>,
	open list <linux-kernel@vger.kernel.org>,
	dri-devel@lists.freedesktop.org,
	"open list:DRM DRIVER FOR QXL VIRTUAL GPU" 
	<virtualization@lists.linux-foundation.org>,
	Dave Airlie <airlied@redhat.com>,
	"open list:DRM DRIVER FOR QXL VIRTUAL GPU" 
	<spice-devel@lists.freedesktop.org>
Subject: Re: [PATCH v2 10/11] drm/qxl: rework cursor plane
Date: Thu, 18 Feb 2021 14:33:11 +0100	[thread overview]
Message-ID: <2d7a649c-bf1d-aa41-8d3c-af9746b94bc0@suse.de> (raw)
In-Reply-To: <20210218115044.7tsi2szbdlw6lvdi@sirius.home.kraxel.org>

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Hi

Am 18.02.21 um 12:50 schrieb Gerd Hoffmann:
>    Hi,
> 
>> I'm still trying to wrap my head around the qxl cursor code.
>>
>> Getting vmap out of the commit tail is good, but I feel like this isn't
>> going in the right direction overall.
>>
>> In ast, these helper functions were only good when converting the drvier to
>> atomic modesetting. So I removed them in the latst patchset and did all the
>> updates in the plane helpers directly.
> 
> I see the helper functions more as a way to get some structure into the
> code flow.  The callbacks are easier to read if they just call helper
> functions for stuff which needs more than a handful lines of code
> (patch 9/11 exists for the same reason).
> 
> The helpers also make it easier move work from one callback to another,
> but that is just a useful side-effect.
> 
> I had considered making that two separate patches, one factor out code
> into functions and one moving the calls.  Turned out to not be that easy
> though, because the old qxl_cursor_atomic_update() code was a rather
> hairy mix of qxl_create_cursor() + qxl_primary_apply_cursor() +
> qxl_primary_move_cursor().
> 
>> For cursor_bo itself, it seems to be transitional state that is only used
>> during the plane update and crtc update . It should probably be stored in a
>> plane-state structure.
>>
>> Some of the primary plane's functions seem to deal with cursor handling.
>> What's the role of the primary plane in cursor handling?
> 
> It's a quirk.  The qxl device will forget the cursor state on
> qxl_io_create_primary(), so I have to remember the cursor state
> and re-establish it by calling qxl_primary_apply_cursor() again.
> 
> So I'm not sure sticking this into plane state would work.  Because of
> the quirk this is more than just a handover from prepare to commit.
> 
>> For now, I suggest to merge patch 1 to 8 and 11; and move the cursor patches
>> into a new patchset.
> 
> I can merge 1-8, but 11 has to wait until the cursor is sorted.
> There is a reason why 11 is last in the series ;)
> 
>> I'd like ot hear Daniel's opinion on this. Do you have
>> further plans here?
> 
> Well.  I suspect I could easily spend a month cleaning up and party
> redesign the qxl driver (specifically qxl_draw.c + qxl_image.c).
> 
> I'm not sure I'll find the time to actually do that anytime soon.
> I have plenty of other stuff on my TODO list, and given that the
> world is transitioning to virtio-gpu the priority for qxl isn't
> that high.

Well, in that case:

Acked-by: Thomas Zimmermann <tzimmermann@suse.de>

for patches 9 and 10. Having the vmap calls fixed is at least worth it.

Best regards
Thomas

> 
> So, no, I have no short-term plans for qxl beyond fixing pins +
> reservations + lockdep.
> 
> take care,
>    Gerd
> 
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> 

-- 
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Felix Imendörffer

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