Messages in this thread | | | From | Kay Sievers <> | Date | Thu, 10 Dec 2009 16:17:00 +0100 | Subject | Re: [PATCH 2/3] gpiolib: add support for having symlinks under gpio class directory |
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On Thu, Dec 10, 2009 at 15:49, Greg KH <gregkh@suse.de> wrote: > On Thu, Dec 10, 2009 at 04:32:17PM +0200, Jani Nikula wrote: >> We simply decided to extend gpio_export_link(). When it is called >> with 'dev == NULL' (no driver), it creates an additional symlink >> in /sys/class/gpio/ >> >> # ls -l /sys/class/gpio/ >> --w------- 1 root 0 4096 Jan 1 00:00 export >> lrwxrwxrwx 1 root 0 0 Jan 1 00:00 power_button -> ../../devices/virtual/gpio/gpio25 >> lrwxrwxrwx 1 root 0 0 Jan 1 00:00 gpio25 -> ../../devices/virtual/gpio/gpio25 >> lrwxrwxrwx 1 root 0 0 Jan 1 00:00 gpio38 -> ../../devices/virtual/gpio/gpio38 >> ... >> >> This is exactly what our patchset allows to do. >> >> An alternative would be a dummy driver just to create a home in sysfs >> for the standalone GPIOs and use the gpio_export_link() to make the >> links there. >> >> Any other suggestions?
We can not do anything like that. The symlink name must always match the name in /sys/devices/, and it must be a 1:1 relation. We can not allow anything else, it confuses tools which rightfully expect this.
You could convert the class to a "bus", the /sys/class layout is pretty much broken by design, and should better be avoided. It's not extensible, flat in its layout, and today just a too dumb version of the "bus" subsystem which does not have all these limitations.
All the device links would show up in /sys/bus/gpio/devices/, here you have the same rules as in /sys/class/: no additional symlinks, the same names as in /sys/devices -- but you could add a custom folder to the /sys/bus/gpio/ directory where you could do whatever fits your needs. :)
Thanks, Kay -- 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/
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