linux-kernel - Re: [PATCH] video/aperture: fix typos

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Message-ID: <fabb3433-e8f1-f162-891b-8aac28ef7662@189.cn>
Date:   Wed, 5 Apr 2023 17:55:47 +0800
From:   Sui Jingfeng <15330273260@....cn>
To:     Javier Martinez Canillas <javierm@...hat.com>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Maxime Ripard <mripard@...nel.org>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>, Li Yi <liyi@...ngson.cn>,
        Christian Koenig <christian.koenig@....com>,
        Helge Deller <deller@....de>,
        Lucas De Marchi <lucas.demarchi@...el.com>
Cc:     linux-kernel@...r.kernel.org, linux-fbdev@...r.kernel.org,
        dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH] video/aperture: fix typos

Hi,

thanks you for the time and effort  for reviewing.

On 2023/4/4 19:03, Javier Martinez Canillas wrote:
> Javier Martinez Canillas <javierm@...hat.com> writes:
>
> [...]
>
>>>>    	/*
>>>>    	 * Remove the device from the device hierarchy. This is the right thing
>>>> -	 * to do for firmware-based DRM drivers, such as EFI, VESA or VGA. After
>>>> +	 * to do for firmware-based fb drivers, such as EFI, VESA or VGA. After
>>> That sentences is not well phrased. Maybe say 'This is required for
>>> firmware-provided graphics, such as EFI, VESA or VGA.'
>>>
>> Graphic drivers or display drivers would indeed be more accurate here. But
>> I think that "fb drivers" is still well pharsed since the are other places
>> where either fbdev or DRM drivers for firmware-provided framebuffers are
>> named like that.
>>
> Sui,
>
> Maybe you could post a follow-up patch to improve the comment as suggested
> by Thomas?
>
Yes, certainly.


This is the right thing to do for conflicting drivers takes over the 
hardware resource required.


But the comments is actually nearly perfect in overall, it has some 
difficulty to improve

the perfection.  Below is my personal understanding toward the above 
sentence.


efifb and simplefb belong to the class of firmware based framebuffer driver.

They are generic and platform agnostic, yet they have to relay on the 
firmware

to passing fb format, fb size, fb base address, fb resolution and fb 
stride etc to the kernel.

Linux kernel using those information to fill the global screen_info 
structure.

sysfb_init() then using the global screen_info to  create a platform device,

the device will be claimed by efifb or simplefb driver finally. This is 
a hand over solution.

It relay on the firmware setup such a framebuffer and hand over the 
state(this is

actually a kind of modeset state) to kernel.


efifb only own the potential hardware resource for a very short time if a

conflicting drm driver probe successfully.


For the platform/graphics without  a drm driver, developers may choose to

use efifb driver as a replacement.  So, there are no conflicting happen on

such a case. The `nomodeset` kernel cmd options can also be used for

debugging and testing purpose if the more intelligent drm driver is broken

due to bugs.