On Friday, December 15, 2023 2:10:15 AM PST Johan Hovold wrote: > On Mon, Oct 02, 2023 at 05:11:35PM -0700, Stan Bertrand wrote: > > From: Stanislas Bertrand <stanislasbertrand@xxxxxxxxx> > > > > Use ftdi serial number on gpiochip label. > > Allows to interface with gpiod utils using the serial number: > > > > $ gpiodetect > > gpiochip5 [ftdi-cbus-FTRelay2] (4 lines) > > gpiochip6 [ftdi-cbus] (4 lines) > > gpiochip7 [ftdi-cbus-A106TPEC] (4 lines) > > > > $ gpioget ftdi-cbus-FTRelay2 2 > > 0 > > I don't think this is a good idea, for example, as not all devices have > a unique serial string. The goal is to identify the gpiochip corresponding to a known FTDI device. If serials are not unique, it can still differentiate others. A device serial can be set (FT Prog, Python lib, ...) for direct of access. > Looks like the naming of gpiochips are all over the place, and ideally > this should not have been something that was left up to individual > driver to decide. > > I see several drivers using the name of the corresponding platform > device as label, which works in most cases, but not always either. The > only unique and always available identifier is the gpiochip's place in > the device tree itself. > > For USB, we already encode the bus topology in the USB device names > (e.g. 1-11.5.1) and we could possibly consider using that. But we > already have USB serial devices with multiple GPIO chips so also that > would require some further thought (e.g. using the interface name > instead). The aim is identification while being platform agnostic, device tree or x86. The FTDI serial allows device identification regardless of the system topology. > Johan Thanks, Stan
