Messages in this thread | | | From | David Brownell <> | Subject | Re: [patch/rfc 2.6.25-git] gpio: sysfs interface | Date | Tue, 29 Apr 2008 14:56:52 -0700 |
| |
On Tuesday 29 April 2008, Trent Piepho wrote: > > Sorry if I'm being dense; how do you want this bit to work? As I see > > it, there are a few options: > > > > 1) Have the files named as you suggest and all of them always present, > > albeit read-only until export. Very easy to use, easy to discover which > > file is which, a decent bit of memory usage having them all listed. > > Well, is it really that much? There are 579 files under /sys/class/tty. But > suppose it is too much (why isn't tty too much then?), then we can do 3.
I just ssh'd into three embedded boards I have handy, and they have respectively four, four, and seven entries there. That "seven" case is actually incorrect ... the other three serial ports aren't connected to anything.
So: yes, adding a few hundred useless sysfs nodes *IS* a problem in the target environment of embedded boards.
Note that "read-only until export" is far from straightforward to achieve.
> > 3) Have the files named as you suggest, explicit export/request but > > better parsing behind the control file so something like > > echo "export pca9557-0:5" > control > > works. Very very nice for the user, big heavy back end. > > The back end doesn't seem that big to me. Here's code for it.
Which fails in a common case: chip labels are not unique.
> If anything, > the parsing code is simpler than what David has.
Apples vs oranges. Use the same command syntax if you're going to make comparisons; I can save even more with "+export/-unexport" syntax. For comparable syntax, your stuff *IS* bigger.
> David's code for parsing the control file plus code for generating a mapping > range file would certainly be larger.
The #3 option presumes some file listing chips and ranges too, since GPIOs are exported only on demand. Ditto #2 and #4...
- Dave
-- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |