linux-kernel - Re: how to have the kernel do udev's job and autoload the right modules ?

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Date:	Thu, 7 May 2015 12:19:14 -0700 (PDT)
From:	David Lang <david@...g.hm>
To:	Austin S Hemmelgarn <ahferroin7@...il.com>
cc:	linuxcbon linuxcbon <linuxcbon@...il.com>,
	Ken Moffat <zarniwhoop@...world.com>,
	Richard Weinberger <richard@....at>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: how to have the kernel do udev's job and autoload the right
 modules ?

On Thu, 7 May 2015, Austin S Hemmelgarn wrote:

> On 2015-05-06 16:49, David Lang wrote:
>> On Wed, 6 May 2015, linuxcbon linuxcbon wrote:
>> 
>>> On Wed, May 6, 2015 at 7:53 PM, David Lang <david@...g.hm> wrote:
>>>> It's perfectly legitimate to not want to use udev, but that doesn't mean
>>>> that the kernel will (or should) do it for you.
>>>> David Lang
>>> 
>>> When I boot the kernel without modules, I don't have anything working
>>> except "minimal video".
>>> I think the kernel should give a minimal support for network, sound and
>>> video, even if 0 modules are loaded. I am just dreaming,
>> 
>> You can do that, you just need to build in all the network and sound
>> drivers (and pick which driver in the case of conflicts)
>> 
>> There isn't such a thing as a 'generic' network or sound card. For video
>> there is 'VGA video' which is used by default on x86 systems, but even
>> that's a driver that could be disabled.
>> 
> To explain further, video has a standardized hardware level API (VGA and VBE) 
> because it is considered critical system functionality (which is BS in my 
> opinion, you can get by just fine with a serial console, but that's 
> irrelevant to this discussion).  Sound is traditionally not considered 
> critical, and therefore doesn't have a standardized hardware API.  Networking 
> is (traditionally) only considered critical if the system is booting off the 
> network, and therefore only has a standardized API (part of the PXE spec, 
> known as UNDI) on some systems, and even then only when they are configured 
> to netboot (and IIRC, also only when the processor is in real mode, just like 
> for all other BIOS calls).

I don't think that it has anything to do with critical system functionality, but 
rather just the legacy history of the PC clones. At one point VGA was the 
standard, and at that point the different video card manufacturers got into the 
game, but since they all had to boot the system, and the BIOS only knew how to 
talk to a VGA card, all the enhanced cards had to implement VGA so that DOS and 
the BIOS could function. That legacy has continued on the PC clone systems to 
today. Non PC clones didn't have such a standard, and they don't implement VGA 
on their video cards (unless it's a card ported from a PC)

Network cards were never standardized, and were optional add-ons. They also 
weren't needed for the system to boot, so there was never any standard for 
newcomers to implement.

David Lang
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