On Tue, 30 Jun 2009 11:46:04 +0200
"David Müller (ELSOFT AG)" <[email protected]> wrote:
> Hello
>
> While testing Linux kernel 2.6.30 and the i915 driver, i noticed that
> GPIOA is hardwired to be used as the only possible CRTDDC bus.
>
> code snippet from drivers/gpu/drm/i915/intel_crt.c:
>
> 441 /* Set up the DDC bus. */
> 442 intel_output->ddc_bus = intel_i2c_create(dev, GPIOA,
> "CRTDDC_A"); 443 if (!intel_output->ddc_bus) {
>
>
> Using the VGA BIOS configuration program, the I2C bus used for CRTDDC
> can be changed according to HW requirements (especially if a DVI-I
> connector is present on the board), so the above restriction brakes
> all platforms not using GPIOA as their CRTDDC bus.
>
> The Xorg Intel graphics driver is at least a little bit more flexible
> by probing GPIOD + GPIOE as well for possible attached CRT devices,
> but i'm not sure if this really sufficient in all cases.
>
> Shouldn't the i915 driver use the information provided by the VBT
> ("crt_ddc_gmbus_pin" field in the "bdb_general_definitions" block) to
> figure out which I2C to use for CRTDDC?
Yes, you're probably right. Cc'ing Ma Ling, who's been working in this
area, for comment.
--
Jesse Barnes, Intel Open Source Technology Center
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