Driver question: multiple instances of same char device

Driver question: multiple instances of same char device

[Jon Dufresne]

I am relatively new to linux device development. And want to understand
Linux conventions.

Suppose I have a PCI card that is represented in the system by a
character device.

If I have two of those PCI cards in the system when the driver module
loads, is it convention to have two different major numbers, or have one
major number and two different minor numbers?

Thanks,
Jon

Re: Driver question: multiple instances of same char device

[Vitaliy Ivanov]

On 7/10/07, Jon Dufresne <jon.dufresne@infinitevideocorporation.com> wrote:
> I am relatively new to linux device development. And want to understand
> Linux conventions.
>
> Suppose I have a PCI card that is represented in the system by a
> character device.
>
> If I have two of those PCI cards in the system when the driver module
> loads, is it convention to have two different major numbers, or have one
> major number and two different minor numbers?
>
> Thanks,
> Jon

You can start your kernel hacking way from ldd. It can be found at:
http://lwn.net/Kernel/LDD3/

There are a few other books by R. Love or Greg KH that you can read.

Such questions are fully covered there.

Best,
Vitaliy

Re: Driver question: multiple instances of same char device

[Jon Dufresne]

Thanks,

I have been using this book as a source, and it is a great one at that.
I thought I read the char device chapter enough times to get what I
needed out of it but apparently not. I just reread it and realized that
my answer was there.


Thanks again,
Jon

On Tue, 2007-07-10 at 16:13 +0300, Vitaliy Ivanov wrote:
> On 7/10/07, Jon Dufresne <jon.dufresne@infinitevideocorporation.com> wrote:
> > I am relatively new to linux device development. And want to understand
> > Linux conventions.
> >
> > Suppose I have a PCI card that is represented in the system by a
> > character device.
> >
> > If I have two of those PCI cards in the system when the driver module
> > loads, is it convention to have two different major numbers, or have one
> > major number and two different minor numbers?
> >
> > Thanks,
> > Jon
> 
> You can start your kernel hacking way from ldd. It can be found at:
> http://lwn.net/Kernel/LDD3/
> 
> There are a few other books by R. Love or Greg KH that you can read.
> 
> Such questions are fully covered there.
> 
> Best,
> Vitaliy
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Re: Driver question: multiple instances of same char device

[Alan Cox]

On Tue, 10 Jul 2007 09:06:36 -0400
Jon Dufresne <jon.dufresne@infinitevideocorporation.com> wrote:

> I am relatively new to linux device development. And want to understand
> Linux conventions.
> 
> Suppose I have a PCI card that is represented in the system by a
> character device.
> 
> If I have two of those PCI cards in the system when the driver module
> loads, is it convention to have two different major numbers, or have one
> major number and two different minor numbers?

Usually one major and two minor, although sysfs and udev deals with much
of it now