On Tue 15 Dec 11:42 CST 2020, Bartosz Golaszewski wrote:
> On Tue, Dec 15, 2020 at 6:02 PM Bjorn Andersson
> <bjorn.andersson@xxxxxxxxxx> wrote:
> >
> > Not all GPIO pins are exposed to the world and this is typically
> > described by not giving these lines particular names, commonly "" or
> > "NC".
> >
> > With the recent introduction of '2cd64ae98f35 ("gpiolib: Disallow
> > identical line names in the same chip")' any gpiochip with multiple such
> > pins will refuse to probe.
> >
> > Fix this by treating "" and "NC" as "no name specified" in
> > gpio_name_to_desc()
> >
> > Fixes: 2cd64ae98f35 ("gpiolib: Disallow identical line names in the same chip")
> > Signed-off-by: Bjorn Andersson <bjorn.andersson@xxxxxxxxxx>
> > ---
> >
> > The introduction of 2cd64ae98f35 breaks pretty much all Qualcomm boards and
> > grepping the DT tree indicates that other vendors will have the same problem.
> >
> > In addition to this the am335x-* boards will also needs "[NC]", "[ethernet]",
> > "[emmc"], "[i2c0]", "[SYSBOOT]" and "[JTAG]" added to this list to allow
> > booting v5.11 with the past and present dtb/dts files.
> >
> > drivers/gpio/gpiolib.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
> > index b3340ba68471..407ba79ae571 100644
> > --- a/drivers/gpio/gpiolib.c
> > +++ b/drivers/gpio/gpiolib.c
> > @@ -302,7 +302,7 @@ static struct gpio_desc *gpio_name_to_desc(const char * const name)
> > struct gpio_device *gdev;
> > unsigned long flags;
> >
> > - if (!name)
> > + if (!name || !strcmp(name, "") || !strcmp(name, "NC"))
> > return NULL;
> >
> > spin_lock_irqsave(&gpio_lock, flags);
> > --
> > 2.29.2
> >
>
> I have a bad feeling about this. This opens the door for all kinds of
> exceptions: "N/A", "none" etc. Depending on whose boards are getting
> broken.
>
> If non-uniqueness of names is needed then let's better revert 2cd64ae98f35.
>
I like the intent of 2cd64ae98f35, but even if we decide what the
"unconnected" name should be we have a slew of boards that won't boot
v5.11-rc1 (or with any pre-v5.11 DTBs).
As such I think we need to revert the "return -EEXIST" part of the
patch.
Looking forward perhaps we should define "" to be the "not a gpio"-name,
revise my patch and fix up the DTs accordingly? And keep the dev_err()
as it currently is?
Regards,
Bjorn
