Re: Prolific ATAPI-USB Bridge

Johannes Erdfelt (jerdfelt@sventech.com)
Thu, 28 Oct 1999 00:55:43 -0400


On Mon, Dec 27, 1999, Doug Alcorn <doug@lathi.net> wrote:
> I would very much like to get an external USB hard driver working. I
> have purchased a BUSlink drive. After talking with BUSlink, they said
> that they were willing to help get any specifications that I needed.
> They purchase the bridge chip-set from Prolific (PL-2307). Their web
> site (http://www.prolific.com.tw) says that the PL-2307 is fully
> compliant with the ATAPI-4 standard and the USB 1.0 standard. There
> is a pretty block diagram of how the chip-set works, but no real
> interface specifications. I have written them asking for better
> specs.

Looks kinda similar to the Bulk Storage spec from their block diagram.
Could you plug in the device and get a descriptor dump from it? It'll
let us better figure out how difficult/easy it is to support.

> I am a complete novice to kernel programming. I have wanted to learn
> to write device drivers for a long time. Right now I am about half
> way through Rubini's _Linux Device Drivers_. I understand most of
> what he is saying, but when I try to compile his examples I have found
> them to be pretty incompatible with the 2.3.x tree. My goal over the
> next two weeks or so is to port/upgrade his examples to work with the
> 2.3.x tree.

The best way to learn the USB code is to look at the already existing
drivers. There is no documentation for it since the code was recently
developed (and is still in development).

> What I am asking now is more about the design of the driver rather
> than the HOWTO. Since the chip-set is a generic ATAPI-USB bridge,
> should the driver be designed more like paride than usb_scsi? To be
> honest, I haven't spent more than a couple of hours studying either of
> these drivers and don't really understand their differences. Can
> someone help me get started on the right foot?

It should be more like usb_scsi than anything else I would guess. Once
we get a descriptor dump, we'll have a better idea.

> BTW, my goal is to be able to use this driver in a month or two. Is
> this unrealistic with a couple of programming hours a day (say roughly
> 40 to 80 hours total)?

Doesn't sound completely unreasonable. It all depends on how comfortable
you feel with programming, the kernel and undocumented interfaces.

There's a mailing list for USB at linux-usb@suse.com. I suggest
subscribing since the biggest hurdle you'll most likely have is the USB
portion since it's the newest/least tested part of the code.

JE

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