[PATCH 3.9] Driver for 7-segment displays connected over GPIOs

Greg Kroah-Hartman gregkh at linuxfoundation.org
Mon Jan 7 13:36:42 EST 2013

On Mon, Jan 07, 2013 at 06:53:57PM +0100, Thomas Petazzoni wrote:
> Dear Greg Kroah-Hartman,
> On Mon, 7 Jan 2013 09:23:40 -0800, Greg Kroah-Hartman wrote:
> > > Not having a kernel driver means that gazillions of applications
> > > re-invent the same piece of code over and over again, have to hardcode
> > > the GPIO numbers for a given piece of hardware, while the kernel
> > > abstract all of this very nicely.
> > 
> > That sounds like a wonderful use of a userspace library to do this
> > properly.  Much like libusb does, right?
> > 
> > I still think as this can be done in userspace, it probably should be.
> So that's why we have drivers/usb/misc/usbsevseg.c in the kernel, which
> uses sysfs files to output text or numbers on a 7-segment display,
> while it could all be done using libusb from userspace? Seems like back
> in 2008 you Signed-off-by on the patch adding this driver :-)

I don't remember what I committed a month ago, let alone 4 years ago.
So trying to use that as an excuse as to why I should take your patch
isn't a really good idea, sorry :)

As Russell points out, if you want this in the kernel, it needs to have
a good userspace api, and that needs a lot more work than just a single
sysfs file.


greg k-h

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