linux-kernel - Re: [RFC 1/3] fbdev: hyperv_fb: Remove hyperv

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Message-ID: <77576214-a849-41d7-bcfe-f9af20ff263b@suse.de>
Date: Wed, 10 Sep 2025 17:48:52 +0200
From: Thomas Zimmermann <tzimmermann@...e.de>
To: Michael Kelley <mhklinux@...look.com>,
 Prasanna Kumar T S M <ptsm@...ux.microsoft.com>,
 "deller@....de" <deller@....de>, "arnd@...db.de" <arnd@...db.de>,
 "soci@....rulez.org" <soci@....rulez.org>,
 "gonzalo.silvalde@...il.com" <gonzalo.silvalde@...il.com>,
 "rdunlap@...radead.org" <rdunlap@...radead.org>,
 "bartosz.golaszewski@...aro.org" <bartosz.golaszewski@...aro.org>,
 "wei.liu@...nel.org" <wei.liu@...nel.org>,
 "ssengar@...ux.microsoft.com" <ssengar@...ux.microsoft.com>,
 "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
 "linux-fbdev@...r.kernel.org" <linux-fbdev@...r.kernel.org>,
 "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>
Subject: Re: [RFC 1/3] fbdev: hyperv_fb: Remove hyperv_fb driver

Hi

Am 10.09.25 um 17:25 schrieb Michael Kelley:
> From: Thomas Zimmermann <tzimmermann@...e.de> Sent: Wednesday, September 10, 2025 2:36 AM
>> Hi
>>
>> Am 09.09.25 um 18:58 schrieb Prasanna Kumar T S M:
>>> The Hyper-V DRM driver is available since kernel version 5.14 and
>>> provides full KMS support along with fbdev emulation via the DRM fbdev
>>> helpers. This makes the hyperv_fb driver redundant, remove it.
>> I'm all for removing obsolete drivers. But hyperv_drm likely first needs
>> to merge the patch at
>> https://lore.kernel.org/dri-devel/20250904145806.430568-5-tzimmermann@suse.de/
>> It's been tested and works well. If maintainers from Microsoft have a
>> look at the patch first, we could possibly land it fairly soon.
> Thomas --
>
> My testing of your v3 patch series for vblank timers ended up getting a
> WARN_ON after about 3 days of usage. See [1]. So I don't think it's 100%
> ready yet.

Yeah, I've seen your message, but didn't have time to investigate yet. 
It might not be that much of an issue.

>
> But I agree we need your synthetic vblank timer support to address the
> Hyper-V DRM driver performance issue, before removing the Hyper-V
> fbdev driver. (See [2] for a description of the performance issue.)
>
> Second, isn't it customary to mark a driver as deprecated for a period
> of time, before removing it entirely? I don't see any documentation
> on the deprecation process, but I've seen it done in other cases. If you
> grep through all the kernel Kconfig files, you'll see entries tagged with
> DEPRECATED. Also the driver should be updated to output a deprecated
> message when it loads.

Sure, we can do that.

Best regards
Thomas

>
> Michael
>
> [1] https://lore.kernel.org/dri-devel/BN7PR02MB4148E80C13605F6EAD2B0A03D40FA@BN7PR02MB4148.namprd02.prod.outlook.com/
> [2] https://lore.kernel.org/dri-devel/SN6PR02MB415702B00D6D52B0EE962C98D46CA@SN6PR02MB4157.namprd02.prod.outlook.com/
>
>> Best regards
>> Thomas
>>
>>> Signed-off-by: Prasanna Kumar T S M <ptsm@...ux.microsoft.com>
>>> ---
>>>    MAINTAINERS                     |    1 -
>>>    drivers/video/fbdev/Kconfig     |    8 -
>>>    drivers/video/fbdev/Makefile    |    1 -
>>>    drivers/video/fbdev/hyperv_fb.c | 1386 -------------------------------
>>>    4 files changed, 1396 deletions(-)
>>>    delete mode 100644 drivers/video/fbdev/hyperv_fb.c
>>>

-- 
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstrasse 146, 90461 Nuernberg, Germany
GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman
HRB 36809 (AG Nuernberg)