Messages in this thread | | | Date | Fri, 18 Jul 2008 15:59:52 -0700 | From | Greg KH <> | Subject | Re: [PATCH v2] Add GPIO-based MMC/SD driver |
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On Sat, Jul 19, 2008 at 12:38:07AM +0200, Michael Buesch wrote: > Thanks for the comments. > > On Saturday 19 July 2008 00:10:37 Randy Dunlap wrote: > > > +To add a new device, simply echo the configuration string to the "add" file. > > > +The config string is composed out of the following elements: > > > + > > > +DEVNAME DIpin DOpin CLKpin CSpin SPIMODE MAXBUSSPEED NO_SPI_DELAY CSACTIVELOW > > > + > > > +DEVNAME is a unique name string for the device. > > > +DIpin is the SPI DI GPIO pin. > > > +DOpin is the SPI DO GPIO pin. > > > +CLKpin is the SPI CLOCK GPIO pin. > > > +CSpin is the SPI CHIPSELECT GPIO pin. > > > +SPIMODE is the hardware mode the device will run at. Can be 0-3. > > > +MAXBUSSPEED is the maximum bus speed in Hertz. > > > +NO_SPI_DELAY can be 1 or 0. If it is 1, then the lowlevel SPI delay > > > +will not be performed. This is not standards compliant, but may be required > > > +to gain reasonable speeds on embedded hardware. > > > +CSACTIVELOW can be 1 or 0. If it is 1, the chip is considered to be selected, if CS > > > +is at a logical 0. > > > + > > > > Would this be better done via configfs? sysfs files are supposed to be > > single-value files. > > > Well, I really want to avoid over-engineering this thing. > I thought about using configfs, but that would require to keep lots of state > information across the operations. > So one would have to allocate a device with mkdir. Then configure the parameters. > And then somehow tell the kernel to register it. State has to be maintained over > this time and I'm not sure how that "register" operation would look like. > Writing a "1" to a "register" file? So why not write all config parameters > to an "add" file and be done with all the stuff. ;) > > It all depends on how you define "one thing per file", IMO. > This "add" file does one thing. It creates a device. We must, of course, pass > some configuration parameters, too.
We have precidence with this for the device id being "added" to a driver at run time in PCI and USB. Not that I really like this, I do think configfs would be better to do this with here instead of sysfs.
That being said, as this is a new sysfs file, please break this documentation up into a file in the Documentation/ABI directory instead of here.
thanks,
greg k-h
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