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@suse.de> Sent: Wednesday, September 10, 2025 2:36 AM

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Hi

Am 09.09.25 um 18:58 schrieb Prasanna Kumar T S M:

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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/ (local)
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/ (local)
[2] https://lore.kernel.org/dri-devel/SN6PR02MB415702B00D6D52B0EE962C98D46CA@SN6PR02MB4157.namprd02.prod.outlook.com/ (local)

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Best regards
Thomas

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Signed-off-by: Prasanna Kumar T S M <redacted>
---
   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)