question about device drivers

[shnackattack]

Hey all!

Couple of questions on device drivers:

Can operating system use device drivers to access a device without the device controller? In otherwords,
do device drivers have to always communicate to a device though a device controller?

Do device controllers always have firmware (software) in them? Where would the device controller usually reside, in the device or the motherboard?

I've looked on the net, but could not find any info on the above questions?
Thanks

[godzilla]

looks like questions from OS courses etc.

As far as I remember from OS device controllers are used in todays systems but are not required in general and therefore a system may access a device directly without a device controller as long as drivers support such access.

A device controller is usually a mini(dedicated) CPU in itself: it is used to support communication and management of a device in relation with the data sent from/to the system. It may or may not contain any software. For example a printer dating 6 years ago is connected to parallel port and does not have any controller in it. Unless you can call parrallel interface as a device controller. Though it is generaly considered that parallel interface is just a communication port and not a device controller.

I hope this gives some info to you... and just in case do not take my word as perfectly true: as I sayed this is what I remeber from my OS class.

[Ann Bee]

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Ann