linux-kernel - Re: [PATCH] drm/panthor: Set FMODE_UNSIGNED_OFFSET in fop

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Message-ID: <7a568b22-d259-4f04-98f7-b3b25f326037@arm.com>
Date: Mon, 30 Sep 2024 08:52:00 +0100
From: Steven Price <steven.price@....com>
To: Emmanuel Gil Peyrot <linkmauve@...kmauve.fr>
Cc: Christian Brauner <brauner@...nel.org>, Jeff Layton <jlayton@...nel.org>,
 Jan Kara <jack@...e.cz>, Boris Brezillon <boris.brezillon@...labora.com>,
 Liviu Dudau <liviu.dudau@....com>,
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
 Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>,
 David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
 dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/panthor: Set FMODE_UNSIGNED_OFFSET in fop_flags

On 29/09/2024 23:10, Emmanuel Gil Peyrot wrote:
> This fixes a regression introduced in commit
> 641bb4394f405cba498b100b44541ffc0aed5be1.  No panthor device, card or
> render node, could be open() since this commit, returning EINVAL
> instead.  This prevented Mesa from working on SoCs such as the rk3588
> which contains a Mali-G610 GPU.
> 
> The commit mentions which drivers must be changed to set that flag, but
> panthor seemingly got forgotten, triggering the WARN_ON_ONCE() added
> in drm_open_helper().

Hi Emmanuel,

Liviu posted an identical patch earlier:

https://lore.kernel.org/r/20240920102802.2483367-1-liviu.dudau%40arm.com

The problem is because 641bb4394f40 isn't yet back-merged into any DRM
tree we can't merge it yet (as that commit added the definition of
FOP_UNSIGNED_OFFSET).

Liviu was going to ask the DRM maintainers for advice - I'm not sure
what the outcome way. But anyway we should get -rc1 back-merged soon and
then can apply this to drm-misc-fixes.

Thanks,
Steve

> ---
>  drivers/gpu/drm/panthor/panthor_drv.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/gpu/drm/panthor/panthor_drv.c b/drivers/gpu/drm/panthor/panthor_drv.c
> index 34182f67136c..c520f156e2d7 100644
> --- a/drivers/gpu/drm/panthor/panthor_drv.c
> +++ b/drivers/gpu/drm/panthor/panthor_drv.c
> @@ -1383,6 +1383,7 @@ static const struct file_operations panthor_drm_driver_fops = {
>  	.read = drm_read,
>  	.llseek = noop_llseek,
>  	.mmap = panthor_mmap,
> +	.fop_flags = FOP_UNSIGNED_OFFSET,
>  };
>  
>  #ifdef CONFIG_DEBUG_FS