On Wed, May 25, 2011 at 12:07:33PM -0400, Alex Deucher wrote: > On Wed, May 25, 2011 at 4:36 AM, Sascha Hauer <s.hauer@xxxxxxxxxxxxxx> wrote: > > Hi All, > > > > I'm currently looking into implementing a SoC graphics core with KMS. > > > > What I wonder about is the relationship between connectors and encoders. > > On my board I have a sii9022 HDMI encoder connected via i2c. This chip > > supports reading edid data, tracks the connection status of the display > > and needs to be configured when the resolution changes. So my first > > guess is that I have to implement an encoder. looking at struct > > drm_encoder_funcs there are no callbacks suitable for this. struct > > drm_connector_funcs on the other hand has all the callbacks I need. > > Now I look at drivers/gpu/drm/i2c. The drivers there implement a > > drm_encoder_slave which also has all the callbacks I need. So from > > one point of view the functions should be implemented in the connector, > > while in the i2c case it's implemented in the (slave-) encoder. > > Generally I have the feeling that my sii9022 should be both an encoder > > and a connector, but this doesn't fit into the current scheme. > > > > I'm confused. Could someone clarify this a bit? > > The general idea is this: > framebuffer -> crtc -> encoder -> connector -> monitor > > - The framebuffer is just a buffer vram that has an image encoded in > it as an array of pixels. > - The crtc reads the data out of the framebuffer and generates the > video mode timing in conjunction with a PLL. The crtc also determines > what part of the framebuffer is read; e.g., when multi-head is > enabled, each crtc scans out of a different part of vram; in clone > mode, each crtc scans out of the same part of vram. > - The encoder takes the digital bitstream from the crtc and converts > it to the appropriate analog levels for transmission across the > connector to the monitor. > - The connector provides the appropriate physical plug (HDMI, DVI-D, > VGA, S-video, etc.) for the monitor to connect to. > > crtcs are usually routeable and can be connected to one or many > encoders simultaneously. The encoders can also be connected to one or > more connectors (e.g., you might have a single TMDS encoder that is > connected to the digital portion of a DVI-I port and also to a HDMI > port, or you might have a DAC that is connected to a VGA port and an > S-video port). Finally i2c lines are associated with connectors, > since generally the i2c pins are wired to the connector and in many > cases, each connectors has it's own i2c line. For example, you might > have a single TMDS encoder that is wired to a DVI-D port with its own > i2c line and an HDMI port with its own i2c line. Each connector may > have it's own hotplug (HPD) pin as well. That way you could query the > EDID from each connector separately for example. > > Is the sii9022 being driven by the output of a DVO encoder from your > display hw? If so your display path would look like: > > crtc -> DVO (master encoder) -> sii9022 (slave encoder) -> HDMI plug -> monitor > > The general GPU driver might register the i2c buses that are used by > the various parts (encoder, connector), then it's just a matter of > plugging in the right parts for each component (e.g. you'd hook up the > sii9022 i2c control bus to the DVO encoder, and the ddc i2c bus to the > hdmi connector object, etc.). > > I hope this helps. Thanks, that helped a lot. There are most probably more questions but for the moment I'll continue digging myself through the maze ;) Thanks Sascha -- Pengutronix e.K. | | Industrial Linux Solutions | http://www.pengutronix.de/ | Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 | _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/dri-devel
