Message-ID: <417965E7.8010408@techsource.com>
Date: Fri, 22 Oct 2004 15:56:23 -0400
From: Timothy Miller <miller@techsource.com>
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To: Jeff Garzik <jgarzik@pobox.com>
CC: Alan Cox <alan@lxorguk.ukuu.org.uk>, Jon Smirl <jonsmirl@gmail.com>,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: HARDWARE: Open-Source-Friendly Graphics Cards -- Viable?
References: <4176E08B.2050706@techsource.com> <4177DF15.8010007@techsource.com> <4177E50F.9030702@sover.net> <200410220238.13071.jk-lkml@sci.fi> <41793C94.3050909@techsource.com> <417955D3.5020206@pobox.com> <41795DEA.8050309@techsource.com> <41796083.9060301@pobox.com>
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Jeff Garzik wrote:
> Timothy Miller wrote:
> 

> 
>> At this moment, I'm taking a cue from the Linux driver ABI and 
>> thinking that standardizing the interface would be more limiting than 
>> helpful. 
> 
> 
> No offense, but I strongly disagree :)
> 
> Standardizing the hardware interface lowers the cost of doing an OS 
> driver for every chip maker that implements the interface.  The more 
> chip makers that implement the interface, the greater the cost savings.
> 
> Concrete examples:
> * IDE BMDMA interface on PCI.  Practically every ATA chipset in 
> production supports this interface.  As a consequence, each individual 
> ATA driver mainly involves setting chip-specific timings, and not much 
> else.
> 
> * tulip (ethernet MAC).  Its ring and register designs were widely 
> imitated across ethernet NICs; as a result, each ethernet driver is 
> mainly a "paint by numbers" affair.
> 
> * the new AHCI SATA interface, which Intel has on all its new 
> motherboards, and SiS soon will as well (as will others, I hope).

Sure, but those standards had time to evolve to where they are.  I don't 
have that luxury in many respects.

> 
> 
>> While it might be a pain to have to carry around multiple driver 
>> versions, the fact that it's all open source kinda makes it easy to 
>> make drastic changes without hurting anything.
> 
> 
> Ever-changing hardware and firmware interfaces are a huge pain.  I've 
> been writing and maintaining drivers for years... I feel this pain every 
> day :)
> 
> You want to design a hardware interface that allows you to upgrade and 
> enhance your hardware over time, while keeping the changes to the 
> hardware<->OS interface itself to a _bare minimum_.  That's why I 
> suggested the microcontroller+GPU approach.  The microcontroller's 
> firmware can be used to mask the transition between GPU revisions.
> 
> Drivers live for many years, even decades, and long after the hardware 
> they support has been EOL'd.  It's in everybody's best interests to keep 
> the changes to the drivers to a minimum.

Ok, let me say this:  I will not change something I don't have to 
change, but I'm not going to be held back (and hold everyone else back) 
by some mistake I made in the past.

> 
>> Plus, I don't expect to get it perfect the first time.  The first design 
> 
> 
> Part of open source is open development.  If you develop the hardware 
> interface in public, actively soliciting feedback during development, 
> you'll wind up with a much better interface.

Fair enough, although the problem of a competitor getting the jump on us 
that way is yet to be addressed.

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