[ECOS] Re: Device driver implementation questions

Mike Sweeney msweeney77@gmail.com
Fri Jun 15 09:43:00 GMT 2007


On 6/14/07, Grant Edwards <grante@visi.com> wrote:
> On 2007-06-14, Mike Sweeney <msweeney77@gmail.com> wrote:
>
> > I am finding the way device drivers are implemented in eCos to be
> > slightly confusing so was looking for some help. The main source of my
> > confusion is the need for some sort of interface under the io package
> > and then another part of the driver in the devs package. I have looked
> > at examples like the serial driver and understand how it works in that
> > context, but am having trouble seeing the bigger picture. Should
> > drivers for all types of devices follow this split implementation
> > design? Furthermore, can someone provide me an analogy between the
> > eCos driver model and Linux, for example? I don't see this two layer
> > method in Linux so am hoping someone can clarify this.
>
> Linux has almost the exact same two layer method for many
> drivers:
>
>   Serial drivers: There is a line-discipline layer which
>   provides the application with open/close/read/write calls.
>   That corresponds to the "io" stuff in eCos. The
>   line-discipline layer then calls lower-level
>   hardware-specific drivers for different sorts of serial
>   ports.  That corresponds to the "dev" stuff in eCos.
>
>   SCSI drivers: Pretty much the same -- there's a generic layer
>   that provides an API to the user and then a lower layer that
>   talks to individual SCSI controllers (or other hardware).
>
> There are probably other examples (VFS on top of the individual
> filesystem modules, 80211 on top of various card drivers).
>
> --
> Grant Edwards                   grante             Yow! FUN is never having to
>                                   at               say you're SUSHI!!
>                                visi.com

Thanks for the information, that clarifies things for me.

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