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A Call For Deprecating The Linux Frame-Buffer FBDEV

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  • #16
    Originally posted by curaga View Post
    X runs on fbdev, wayland runs on X, and kmscon is a huge NIH-ism when fbcon works well. :P
    X runs on fbdev w/ limited feature set (no modesetting). But there is also a basic modesetting driver now so X does not require fbdev.

    Wayland on X probably doesn't really count, if you are talking about kernel display interfaces. X is not a kernel display subsystem.

    And I've tried kmscon recently.. it is pretty nice actually, and way faster than fbcon, and supports hotplug. And I suppose some people would appreciate the possibility for proper support of unicode. But I guess one person's NIH-ism is another person's moving-on-and-creating-something-with-modern-features-ism :-P

    Originally posted by curaga View Post
    Multiple displays and hotplug, neither are needed in typical embedded cases, when there's only one display for the lifetime of the device. I'm not seeing whether there's any reason at all for these deployments to switch apis, the fact that someone wants to deprecate a well working api doesn't really count.
    Perhaps. But KMS doesn't hurt in these cases, and it would be nice to get to a point where everyone is using one API that can scale across a wide variety of display use cases, vs starting off w/ an overly simple display API and then later realize that you have painted yourself into a corner when you realize you need to do something more advanced.

    Obviously it won't be an overnight change.. fbdev won't be removed soon. But the current situation of two display subsystems is not ideal. So it is best to start nudging things towards KMS.

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    • #17
      Originally posted by robclark View Post
      yup.. existing drivers wouldn't be removed any time quickly. The point/suggestion is, that *new* drivers should be written as drm/kms drivers rather than fbdev drivers.
      Rob, is there a document available on how to write a KMS driver for dumb framebuffer devices?

      (I sort of maintain 2 fb drivers for some fringe MIPS hardware and was pondering a rewrite
      of the more advanced one (it's basically a lcd controller which can source up to 4 arbitrarily-sized
      windows to compose a final picture, including alpha blending. The DMA controller can even
      be used to do bitblits))

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      • #18
        fbdev does not support multi-head. That alone is a major issue.

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        • #19
          Originally posted by mlau View Post
          Rob, is there a document available on how to write a KMS driver for dumb framebuffer devices?
          Documentation written by Laurent covers KMS in general not specific to simple devices vs. complex devices:
          http://lwn.net/Articles/499261/

          Two simple KMS drivers:
          http://lists.freedesktop.org/archive...il/021249.html
          http://lists.freedesktop.org/archive...il/021245.html

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          • #20
            Originally posted by agd5f View Post
            Documentation written by Laurent covers KMS in general not specific to simple devices vs. complex devices:
            http://lwn.net/Articles/499261/

            Two simple KMS drivers:
            http://lists.freedesktop.org/archive...il/021249.html
            http://lists.freedesktop.org/archive...il/021245.html
            Thanks. Exactly what I was looking for.

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            • #21
              Originally posted by agd5f View Post
              Documentation written by Laurent covers KMS in general not specific to simple devices vs. complex devices:
              http://lwn.net/Articles/499261/
              Fyi, Laurent has posted the html generated from his documentation patch, which might be a bit more convenient to look at:

              http://www.ideasonboard.org/media/drm/index.html

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              • #22
                The bg image on that site makes it unreadable:



                Does he come on phoronix?

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                • #23
                  Originally posted by curaga View Post
                  The bg image on that site makes it unreadable:



                  Does he come on phoronix?
                  no idea.. but at least in chromium it looks ok without the bg img being as intrusive as that screenshot

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                  • #24
                    it looks different in firefox (still not a good idea (haha pun intended) to have that as a background)



                    /edit:
                    And it's valid xhtml + css

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