Messages in this thread | | | Date | Tue, 19 May 2020 10:57:03 +0200 | From | Johan Hovold <> | Subject | Re: [PATCH 2/2] usb: serial: xr_serial: Add gpiochip support |
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On Wed, Apr 29, 2020 at 06:19:18PM +0530, Manivannan Sadhasivam wrote:
> On Wed, Apr 29, 2020 at 02:12:24PM +0200, Linus Walleij wrote: > > On Tue, Apr 28, 2020 at 9:57 PM <mani@kernel.org> wrote: > > > > > From: Manivannan Sadhasivam <mani@kernel.org> > > > > > > Add gpiochip support for Maxlinear/Exar USB to serial converter > > > for controlling the available gpios. > > > > > > Cc: Linus Walleij <linus.walleij@linaro.org> > > > Cc: linux-gpio@vger.kernel.org > > > Signed-off-by: Manivannan Sadhasivam <mani@kernel.org>
> > I would change this: > > > > port_priv->gc.label = "xr_gpios"; > > > > to something that is device-unique, like "xr-gpios-<serial number>" > > which makes it easy to locate the GPIOs on a specific serial converter > > for lab use. However the USB serial maintainers know better what > > to use here. Whatever makes a USB-to-serial unique from a TTY > > point of view is probably fine with me too. > > > > My idea is that people might want to know which USB cable > > this is sitting on, so I have this USB cable and from this label > > I can always figure out which GPIO device it is.
I think we've had this discussion before. First, not every device has a unique serial number. Second, we already have a universal way of distinguishing devices namely by using the bus topology. That's available through sysfs and shouldn't have to be be re-encoded by every driver in the gpiochip name.
> Sounds reasonable. I can postfix the PID as below: > > port_priv->gc.label = devm_kasprintf(port->dev, GFP_KERNEL, "XR%04x", > port_priv->idProduct); > > So this will become, "XR1410".
So this doesn't really buy us anything; what if you have two of these devices?
Johan
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