Re: understanding of sysfs.

[Madhu K]

On Tue, May 23, 2017 at 2:53 PM, Greg KH  wrote:

> On Tue, May 23, 2017 at 12:58:07PM +0530, Madhu K wrote:
> > Hi Greg,
> >
> > Thanks for your response.
> >
> >
> > On Tue, May 23, 2017 at 12:04 PM, Greg KH  wrote:
> >
> > On Tue, May 23, 2017 at 11:58:31AM +0530, Madhu K wrote:
> > > Hi All,
> > >
> > > why there is no character device entry present in /sys/class?
> where as
> > block
> > > and net device entries are present.
> >
> > I see character devices there, but not the device nodes.  I don't see
> > block device nodes there either.
> >
> >
> > If I am wrong please correct me, there is a folder called block in
> /sys/class.
> > is block not containing block device nodes?
>
> Nope, look closer :)
>

I checked the block folder, the entries which are present in
/sys/class/block are softlink to /sys/devices nodes. what i understand from
this is, all block net and char node entries are present in /sys/devices.
Am i correct?


>
> > > Not only in /sys/class, for that matter why there is no character
> device
> > > entries present in /sys file system.
> >
> > What do you exactly mean by "character device entries"?
> >
> >
> > like block and net why there is no char folder
>
> Again, look closer please.
>
> > > please help me to understand for what purpose char devices are
> kept away
> > from /
> > > sys file system.
> >
> > Have you read the driver model chapter in the Linux Device drivers
> book,
> > or the in-kernel sysfs documentation?
>
> Again, please read all of the copious documentation that we have written
> already about this topic.  If after that, you still have questions, I
> will be more than glad to help answer them.
>
> thanks,
>
> greg k-h
>
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Re: understanding of sysfs.

[Greg KH]

On Mon, May 29, 2017 at 10:58:09AM +0530, Madhu K wrote:
> 
> 
> On Tue, May 23, 2017 at 2:53 PM, Greg KH  wrote:
> 
> On Tue, May 23, 2017 at 12:58:07PM +0530, Madhu K wrote:
> > Hi Greg,
> >
> > Thanks for your response.
> >
> >
> > On Tue, May 23, 2017 at 12:04 PM, Greg KH  wrote:
> >
> >     On Tue, May 23, 2017 at 11:58:31AM +0530, Madhu K wrote:
> >     > Hi All,
> >     >
> >     > why there is no character device entry present in /sys/class? 
> where
> as
> >     block
> >     > and net device entries are present.
> >
> >     I see character devices there, but not the device nodes.  I don't 
> see
> >     block device nodes there either.
> >
> >
> > If I am wrong please correct me, there is a folder called block in /sys/
> class.
> > is block not containing block device nodes? 
> 
> Nope, look closer :)
> 
> 
> I checked the block folder, the entries which are present in /sys/class/block
> are softlink to /sys/devices nodes.

What do you exactly mean by "nodes"?  /sys/class/block/ points to the
block device "class devices" in the kernel device hierarchy, just like
the other /sys/class/* entries point to other class devices.

> what i understand from this is, all block net and char node entries
> are present in /sys/devices. Am i correct?

Again, what do you mean by a "node"?  Did you read the documentation
about sysfs and the driver model?

thanks,

greg k-h

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