[PATCH 00/10] MCDE: Add frame buffer device driver

Fri Nov 12 11:46:53 EST 2010

Hi Alex,
Do you have any idea of how we should use KMS without being a "real" drm 3D device? Do you mean that we should use the KMS ioctls on for display driver? Or do you mean that we should expose a /dev/drmX device only capable of KMS and no GEM?

What if we were to add a drm driver for 3D later on. Is it possible to have a separate drm device for display and one for 3D, but still share "GEM" like buffers between these devices? It look like GEM handles are device relative. This is a vital use case for us. And we really don't like to entangle our MCDE display driver, memory manager and 3D driver without a good reason. Today they are maintained as independent drivers without code dependencies. Would this still be possible using drm? Or does drm require memory manager, 3D and display to be one driver? I can see the drm=graphics card on desktop machines. But embedded UMA systems doesn't really have this dependency. You can switch memory mamanger, 3D driver, display manager in menuconfig independently of the other drivers. Not that it's used like that on one particular HW, but for different HW you can use different parts. In drm it looks like all these pieces belong together.

Do you think the driver should live in the "gpu/drm" folder, even though it's not a gpu driver?

Do you know of any other driver that use DRM/KMS API but not being a PC-style graphics card that we could look at for inspiration?

And GEM, is that the only way of exposing graphics buffers to user space in drm? Or is it possible (is it ok) to expose another similar API? You mentioned that there are TTM and GEM, do both expose user space APIs for things like sharing buffers between processes, security, cache management, defragmentation? Or are these type of features defined by DRM and not TTM/GEM?

/BR
/Marcus

> -----Original Message-----
> From: Alex Deucher [mailto:alexdeucher at gmail.com]
> Sent: den 12 november 2010 16:53
> To: Jimmy RUBIN
> Cc: linux-fbdev at vger.kernel.org; linux-arm-kernel at lists.infradead.org;
> linux-media at vger.kernel.org; Linus WALLEIJ; Dan JOHANSSON; Marcus
> LORENTZON
> Subject: Re: [PATCH 00/10] MCDE: Add frame buffer device driver
> 
> On Fri, Nov 12, 2010 at 8:18 AM, Jimmy RUBIN
> <jimmy.rubin at stericsson.com> wrote:
> > Hi Alex,
> >
> > Good point, we are looking at this for possible future improvements
> but for the moment we feel like
> > the structure of drm does not add any simplifications for our driver.
> We have the display manager (MCDE DSS = KMS) and the memory manager
> (HWMEM = GEM) that could be migrated to drm framework. But we do not
> have drm drivers for 3D hw and this also makes drm a less obvious
> choice at the moment.
> >
> 
> You don't have to use the drm strictly for 3D hardware.  historically
> that's why it was written, but with kms, it also provides an interface
> for complex display systems.  fbdev doesn't really deal properly with
> multiple display controllers or connectors that are dynamically
> re-routeable at runtime.  I've seen a lot of gross hacks to fbdev to
> support this kind of stuff in the past, so it'd be nice to use the
> interface we now have for it if you need that functionality.
> Additionally, you can use the shared memory manager to both the
> display side and v4l side.  While the current drm drivers use GEM
> externally, there's no requirement that a kms driver has to use GEM.
> radeon and nouveau use ttm internally for example.  Something to
> consider.  I just want to make sure people are aware of the interface
> and what it's capable of.
> 
> Alex
> 
> > Jimmy
> >
> > -----Original Message-----
> > From: Alex Deucher [mailto:alexdeucher at gmail.com]
> > Sent: den 10 november 2010 15:43
> > To: Jimmy RUBIN
> > Cc: linux-fbdev at vger.kernel.org; linux-arm-
> kernel at lists.infradead.org; linux-media at vger.kernel.org; Linus WALLEIJ;
> Dan JOHANSSON
> > Subject: Re: [PATCH 00/10] MCDE: Add frame buffer device driver
> >
> > On Wed, Nov 10, 2010 at 7:04 AM, Jimmy Rubin
> <jimmy.rubin at stericsson.com> wrote:
> >> These set of patches contains a display sub system framework (DSS)
> which is used to
> >> implement the frame buffer device interface and a display device
> >> framework that is used to add support for different type of displays
> >> such as LCD, HDMI and so on.
> >
> > For complex display hardware, you may want to consider using the drm
> > kms infrastructure rather than the kernel fb interface.  It provides
> > an API for complex display hardware (multiple encoders, display
> > controllers, etc.) and also provides a legacy kernel fb interface for
> > compatibility.  See:
> > Documentation/DocBook/drm.tmpl
> > drivers/gpu/drm/
> > in the kernel tree.
> >
> > Alex
> >
> >>
> >> The current implementation supports DSI command mode displays.
> >>
> >> Below is a short summary of the files in this patchset:
> >>
> >> mcde_fb.c
> >> Implements the frame buffer device driver.
> >>
> >> mcde_dss.c
> >> Contains the implementation of the display sub system framework
> (DSS).
> >> This API is used by the frame buffer device driver.
> >>
> >> mcde_display.c
> >> Contains default implementations of the functions in the display
> driver
> >> API. A display driver may override the necessary functions to
> function
> >> properly. A simple display driver is implemented in display-
> generic_dsi.c.
> >>
> >> display-generic_dsi.c
> >> Sample driver for a DSI command mode display.
> >>
> >> mcde_bus.c
> >> Implementation of the display bus. A display device is probed when
> both
> >> the display driver and display configuration have been registered
> with
> >> the display bus.
> >>
> >> mcde_hw.c
> >> Hardware abstraction layer of MCDE. All code that communicates
> directly
> >> with the hardware resides in this file.
> >>
> >> board-mop500-mcde.c
> >> The configuration of the display and the frame buffer device is
> handled
> >> in this file
> >>
> >> NOTE: These set of patches replaces the patches already sent out for
> review.
> >>
> >> RFC:[PATCH 1/2] Video: Add support for MCDE frame buffer driver
> >> RFC:[PATCH 2/2] Ux500: Add support for MCDE frame buffer driver
> >>
> >> The old patchset was to large to be handled by the mailing lists.
> >>
> >> Jimmy Rubin (10):
> >>  MCDE: Add hardware abstraction layer
> >>  MCDE: Add configuration registers
> >>  MCDE: Add pixel processing registers
> >>  MCDE: Add formatter registers
> >>  MCDE: Add dsi link registers
> >>  MCDE: Add generic display
> >>  MCDE: Add display subsystem framework
> >>  MCDE: Add frame buffer device driver
> >>  MCDE: Add build files and bus
> >>  ux500: MCDE: Add platform specific data
> >>
> >>  arch/arm/mach-ux500/Kconfig                    |    8 +
> >>  arch/arm/mach-ux500/Makefile                   |    1 +
> >>  arch/arm/mach-ux500/board-mop500-mcde.c        |  209 ++
> >>  arch/arm/mach-ux500/board-mop500-regulators.c  |   28 +
> >>  arch/arm/mach-ux500/board-mop500.c             |    3 +
> >>  arch/arm/mach-ux500/devices-db8500.c           |   68 +
> >>  arch/arm/mach-ux500/include/mach/db8500-regs.h |    7 +
> >>  arch/arm/mach-ux500/include/mach/devices.h     |    1 +
> >>  arch/arm/mach-ux500/include/mach/prcmu-regs.h  |    1 +
> >>  arch/arm/mach-ux500/include/mach/prcmu.h       |    3 +
> >>  arch/arm/mach-ux500/prcmu.c                    |  129 ++
> >>  drivers/video/Kconfig                          |    2 +
> >>  drivers/video/Makefile                         |    1 +
> >>  drivers/video/mcde/Kconfig                     |   39 +
> >>  drivers/video/mcde/Makefile                    |   12 +
> >>  drivers/video/mcde/display-generic_dsi.c       |  152 ++
> >>  drivers/video/mcde/dsi_link_config.h           | 1486
> ++++++++++++++
> >>  drivers/video/mcde/mcde_bus.c                  |  259 +++
> >>  drivers/video/mcde/mcde_config.h               | 2156
> ++++++++++++++++++++
> >>  drivers/video/mcde/mcde_display.c              |  427 ++++
> >>  drivers/video/mcde/mcde_dss.c                  |  353 ++++
> >>  drivers/video/mcde/mcde_fb.c                   |  697 +++++++
> >>  drivers/video/mcde/mcde_formatter.h            |  782 ++++++++
> >>  drivers/video/mcde/mcde_hw.c                   | 2528
> ++++++++++++++++++++++++
> >>  drivers/video/mcde/mcde_mod.c                  |   67 +
> >>  drivers/video/mcde/mcde_pixelprocess.h         | 1137 +++++++++++
> >>  include/video/mcde/mcde.h                      |  387 ++++
> >>  include/video/mcde/mcde_display-generic_dsi.h  |   34 +
> >>  include/video/mcde/mcde_display.h              |  139 ++
> >>  include/video/mcde/mcde_dss.h                  |   78 +
> >>  include/video/mcde/mcde_fb.h                   |   54 +
> >>  31 files changed, 11248 insertions(+), 0 deletions(-)
> >>  create mode 100644 arch/arm/mach-ux500/board-mop500-mcde.c
> >>  create mode 100644 drivers/video/mcde/Kconfig
> >>  create mode 100644 drivers/video/mcde/Makefile
> >>  create mode 100644 drivers/video/mcde/display-generic_dsi.c
> >>  create mode 100644 drivers/video/mcde/dsi_link_config.h
> >>  create mode 100644 drivers/video/mcde/mcde_bus.c
> >>  create mode 100644 drivers/video/mcde/mcde_config.h
> >>  create mode 100644 drivers/video/mcde/mcde_display.c
> >>  create mode 100644 drivers/video/mcde/mcde_dss.c
> >>  create mode 100644 drivers/video/mcde/mcde_fb.c
> >>  create mode 100644 drivers/video/mcde/mcde_formatter.h
> >>  create mode 100644 drivers/video/mcde/mcde_hw.c
> >>  create mode 100644 drivers/video/mcde/mcde_mod.c
> >>  create mode 100644 drivers/video/mcde/mcde_pixelprocess.h
> >>  create mode 100644 include/video/mcde/mcde.h
> >>  create mode 100644 include/video/mcde/mcde_display-generic_dsi.h
> >>  create mode 100644 include/video/mcde/mcde_display.h
> >>  create mode 100644 include/video/mcde/mcde_dss.h
> >>  create mode 100644 include/video/mcde/mcde_fb.h
> >>
> >> --
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