On 12/14/2016 01:56 PM, Greg KH wrote: > On Wed, Dec 14, 2016 at 01:45:30PM +0100, Thomas Petazzoni wrote: >> Hello, >> >> On Tue, 13 Dec 2016 23:55:00 -0800, Jaghathiswari Rankappagounder >> Natarajan wrote: >> >>> Documentation for the binding which provides an interface for adding clock, >>> data and clear signal GPIO lines to control seven segment display. >>> >>> The platform device driver provides an API for displaying on two 7-segment >>> displays, and implements the required bit-banging. The hardware assumed is >>> 74HC164 wired to two 7-segment displays. >>> >>> The character device driver implements the user-space API for letting a user >>> write to two 7-segment displays including any conversion methods necessary >>> to map the user input to two 7-segment displays. >>> >>> Adding clock, data and clear signal GPIO lines in the devicetree to control >>> seven segment display on zaius platform. >>> >>> The platform driver matches on the device tree node; the platform driver also >>> initializes the character device. >>> >>> Tested that the seven segment display works properly by writing to the >>> character device file on a EVB AST2500 board which also has 74HC164 wired >>> to two 7-segment displays. >> >> FWIW, I proposed a driver for seven segment displays back in 2013: >> >> http://lists.infradead.org/pipermail/linux-arm-kernel/2013-January/139986.html >> >> And the feedback from Greg KH was: we don't need a driver for that, do >> it from userspace. See: >> >> http://lists.infradead.org/pipermail/linux-arm-kernel/2013-January/139992.html >> >> So: good luck :-) > > Did anyone ever write a library for this type of thing? > > Again, I don't want to see one-off drivers for random devices like this > that should be able to all be controlled from userspace in a common > manner. Much like we did for fingerprint readers a long long time > ago... > > thanks, > > greg k-h Hi Greg, Actually, it's more than a random interface, a lot of SoCs and boards actually have such displays and it's a pity to use UIO, sysfs gpio bitbanging and all sort of ugly stuff to only print a few characters a simple and clean driver could achieve. Some very well known SoCs even have integrated registers to lower the BOM and bypass the need for a 74HC164 like component and avoid gpio bit banging. My personal concern is that you could also need to drive more segments, thus 7-segments is too restrictive. But this driver is well structured, the gpio-bitbanging sub-driver is welcome. Neil -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
