Date:   Thu, 27 Jan 2022 11:46:44 +0100
From:   Javier Martinez Canillas <javierm@...hat.com>
To:     Pekka Paalanen <ppaalanen@...il.com>
Cc:     linux-kernel@...r.kernel.org,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Jonathan Corbet <corbet@....net>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel.vetter@...ll.ch>,
        dri-devel@...ts.freedesktop.org, linux-doc@...r.kernel.org,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>
Subject: Re: [PATCH] drm/doc: Add section in the introduction page about
 learning material

Hello Pekka,

Thanks a lot for your feedback.

On 1/27/22 10:05, Pekka Paalanen wrote:
> On Thu, 27 Jan 2022 09:20:58 +0100
> Javier Martinez Canillas <javierm@...hat.com> wrote:
> 
>> The Linux DRM subsystem supports complex graphics devices and it could be
>> quite overwhelming for newcomers to learn about the subsystem's internals.
>>
>> There are lots of useful talks, slides and articles available that can be
>> used to get familiar with the needed concepts and ease the learning curve.
>>
>> Add a section to the intro that contains these DRM introductory materials.
>>
>> Suggested-by: Daniel Vetter <daniel.vetter@...ll.ch>
>> Signed-off-by: Javier Martinez Canillas <javierm@...hat.com>
>> ---
>>
>>  Documentation/gpu/introduction.rst | 36 ++++++++++++++++++++++++++++++
>>  1 file changed, 36 insertions(+)
>>
>> diff --git a/Documentation/gpu/introduction.rst b/Documentation/gpu/introduction.rst
>> index 25a56e9c0cfd..35986784f916 100644
>> --- a/Documentation/gpu/introduction.rst
>> +++ b/Documentation/gpu/introduction.rst
>> @@ -112,3 +112,39 @@ Please conduct yourself in a respectful and civilised manner when
>>  interacting with community members on mailing lists, IRC, or bug
>>  trackers. The community represents the project as a whole, and abusive
>>  or bullying behaviour is not tolerated by the project.
>> +
>> +Learning material
>> +=================
>> +
>> +Since the Linux DRM layer supports complex graphics devices, it can be quite
>> +overwhelming for newcomers to get familiar with all the needed concepts and
>> +learn the subsystem's internals.
> 
> Hi,
> 
> this seems to say that DRM is going to be complicated no matter what
> hardware one wants to drive, but is that true?
> 
> Is there no way to say that if your display hardware is simple (no
> GPU), then the driver can be simple to write too?
>

I do wonder how much one could abstract of the uAPI when writing a simpler driver.

In other words, writing the driver should be simple but I believe that grasping
all the needed details about DRM may not be.
 
>> +
>> +To shallow the learning curve, this section contains a list of presentations
>> +and documents that can be used to learn about DRM/KMS and graphics in general.
>> +
>> +The list is sorted in reverse chronological order, to keep the most up-to-date
>> +material at the top. But all of them contain useful information, and it can be
>> +valuable to go through older material to understand the rationale and context
>> +in which the recent changes to the DRM subsystem were made.
>> +
>> +Talks
>> +-----
>> +
>> +* `An Overview of the Linux and Userspace Graphics Stack <https://www.youtube.com/watch?v=wjAJmqwg47k>`_ - Paul Kocialkowski (2020)
>> +* `Getting pixels on screen on Linux: introduction to Kernel Mode Setting <https://www.youtube.com/watch?v=haes4_Xnc5Q>`_ - Simon Ser (2020)
>> +* `An introduction to the Linux DRM subsystem <https://www.youtube.com/watch?v=LbDOCJcDRoo>`_ - Maxime Ripard (2017)
>> +* `Embrace the Atomic (Display) Age <https://www.youtube.com/watch?v=LjiB_JeDn2M>`_ - Daniel Vetter (2016)
>> +* `Anatomy of an Atomic KMS Driver <https://www.youtube.com/watch?v=lihqR9sENpc>`_ - Laurent Pinchart (2015)
>> +* `Atomic Modesetting for Drivers <https://www.youtube.com/watch?v=kl9suFgbTc8>`_ - Daniel Vetter (2015)
>> +* `Anatomy of an Embedded KMS Driver <https://www.youtube.com/watch?v=Ja8fM7rTae4>`_ - Laurent Pinchart (2013
>> +
>> +Slides and articles
>> +-------------------
>> +
>> +* `Understanding the Linux Graphics Stack <https://bootlin.com/doc/training/graphics/graphics-slides.pdf>`_ - Bootlin (2022)
>> +* `DRM KMS overview <https://wiki.st.com/stm32mpu/wiki/DRM_KMS_overview>`_ - STMicroelectronics (2021)
>> +* `Linux graphic stack <https://studiopixl.com/2017-05-13/linux-graphic-stack-an-overview>`_ - Nathan Gauër (2017)
>> +* `The DRM/KMS subsystem from a newbie’s point of view <https://bootlin.com/pub/conferences/2014/elce/brezillon-drm-kms/brezillon-drm-kms.pdf>`_ - Boris Brezillon (2014)
>> +* `A brief introduction to the Linux graphics stack <https://blogs.igalia.com/itoral/2014/07/29/a-brief-introduction-to-the-linux-graphics-stack/>`_ - Iago Toral (2014)
>> +* `The Linux Graphics Stack <https://blog.mecheye.net/2012/06/the-linux-graphics-stack/>`_ - Jasper St. Pierre (2012)
> 
> That's an impressive list of links!
> 
> However, given the discussions that prompted this doc, I think the gist
> is missing. The reader is just flooded with stuff to read and learn
> which can be discouraging.
> 
> Your audience are developers who know nothing about DRM. They may have
> been writing fb drivers instead. The display hardware they want to
> drive has no GPU. Where should they get started? Which presentations to
> read/watch first? Which driver to look at for a simple example?
> 
> Maybe add one more section targeting that specific audience?
>

Yes, I did not ignore your suggestions made over IRC but it's just that I
didn't know to write such section. Maybe we can land this section and then
as a follow-up think how a "Getting started" one should look like ?

Best regards,
-- 
Javier Martinez Canillas
Linux Engineering
Red Hat

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