Re: [PATCH 1/2] ALSA: hda - Continue probing even if i915 binding fails

[David Henningsson <david.henningsson@canonical.com>]

On 2015-06-12 16:14, Takashi Iwai wrote:
> At Fri, 12 Jun 2015 08:37:38 +0200,
> Takashi Iwai wrote:
>>
>> At Fri, 12 Jun 2015 08:17:12 +0200,
>> David Henningsson wrote:
>>> If BIOS disables the power well, then we would get the "audio register
>>> I/O error" in the boot phase, there will be no codecs detected, and thus
>>> no broken sound card showing up.
>>>
>>> The only issue is if the i915 driver disables the power well, but the
>>> case that the i915 should be functioning enough to turn off the power
>>> well at some point, and at the same time so broken that we can't bind to
>>> it, seems extremely unlikely to me.
>>>
>>> Either the i915 driver works, or it does not. In both cases, continuing
>>> probing is the more useful option.
>>
>> I don't see much usefulness there but rather simplicity.
>>
>> The binding with i915 won't happen at the later stage, thus the device
>> is just a placeholder.  Any other goodies by keeping the dead device?
>>
>>>> Fair enough.  Then I'm going to queue the patch below in addition to
>>>> for-linus branch.
>>>
>>> We'll have to agree to disagree on that, then.
>>
>> One point that hasn't been mentioned is the behavior change from the
>> previous kernels.  The previous kernels abort probing, and it was OK
>> since we supposed only HSW/BDW before 4.1.  Now, with continuing the
>> probe, user sees the new device that hasn't been there, and yet the
>> device is dead and merely a placeholder.
>
> Is this convincing enough for you?  Or would you still like to make
> the broken HDMI/DP device enabled for HSW/BDW?

I guess the question is whether HDMI/DP can actually work without the 
i915 driver, e g when running with nomodeset. If there is absolutely no 
possibility whatsoever (e g maybe BIOS could set up the device so that 
it works?), then it does not matter much, I suppose.

-- 
David Henningsson, Canonical Ltd.
https://launchpad.net/~diwic