Re: Fw: [3.18.3] poll() on gpio pins broken

[folkert <folkert@xxxxxxxxxxxxxx>]

> > Mmm, I was thinking it would be nice to have a (new, redesigned) sysfs
> > interface for this. :P
> >
> > Aren't we going to make things less accessible if we use a char device?
> 
> Since sysfs has a "one value per file" paradigm, it also has a
> "one context switch per operation" paradigm, meaning any
> efficiency-oriented use cases where a lot of stuff needs to be
> changed in one context switch are by the very construction
> not suitable for sysfs IMO. That is the use case for ioctl()
> operations that can pass an entire struct of stuff over.
> 
> And things like bit-banging a clock+data line which would in
> a sysfs case involve two context switches (one per value, since
> that is one file per GPIO line) in an ioctl() case it would be
> just one, already 50% less context switches for a very basic
> use case.
> 
> But I may be just so wrong ... input welcome.

Another bad thing of the current sysfs versions: it is ascii.
So I need to convert a=1 to a='1' first before write()ing it to the
file. Very inconvenient because it adds boilerplate code.
On the other hand, the sysfs is very much extensible.


Folkert van Heusden

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