On 5/3/2024 1:25 AM, Linus Walleij wrote:
Hi Dough, thanks for your patch!
Thanks for your review!
"Communication is hard" and I may be confused about your confusion, but hopefully we can work it out.I'm a bit confused here:
I think we are in agreement here. For extra clarity, I will add that in my understanding pinspec.args[0] corresponds to [GPIO controller offset] and pinspec.args[2] corresponds to [number of pins].On Wed, Apr 24, 2024 at 8:51 PM Doug Berger <opendmb@xxxxxxxxx> wrote:+ /* Ignore ranges outside of this GPIO chip */ + if (pinspec.args[0] >= (chip->offset + chip->ngpio)) + continue; + if (pinspec.args[0] + pinspec.args[2] <= chip->offset) + continue;Here pinspec.args[0] and [2] comes directly from the device tree. The documentation in Documentation/devicetree/bindings/gpio/gpio.txt says:2.2) Ordinary (numerical) GPIO ranges ------------------------------------- It is useful to represent which GPIOs correspond to which pins on which pin controllers. The gpio-ranges property described below represents this with a discrete set of ranges mapping pins from the pin controller local number space to pins in the GPIO controller local number space. The format is: <[pin controller phandle], [GPIO controller offset], [pin controller offset], [number of pins]>; The GPIO controller offset pertains to the GPIO controller node containing the range definition.
So I do not understand how pinspec[0] and [2] can ever be compared to something involving chip->offset which is a Linux-specific offset. It rather looks like you are trying to accomodate the Linux numberspace in the ranges, which it was explicitly designed to avoid.
The struct gpio_chip documentation in include/linux/gpio/driver.h says: > * @offset: when multiple gpio chips belong to the same device this > * can be used as offset within the device so friendly names can > * be properly assigned.It is my understanding that this value represents the offset of a gpiochip relative to the GPIO controller device defined by the GPIO controller node in device tree. This puts it in the same number space as [GPIO controller offset]. I believe it was introduced for the specific purpose of translating [GPIO controller offset] values into Linux-specific offsets, which is why it is being reused for that purpose in this patch.
For GPIO Controllers that contain a single gpiochip the 'offset' member is 0 and the device tree node offsets can be applied directly to the gpiochip. However, when a GPIO Controller contains multiple gpiochips, the device tree node offsets must be translated to each individual gpiochip.
I hope it makes sense now, but if not please help me understand what I may be missing.I just don't get it. So NACK until I understand what is going on here. Yours, Linus Walleij
Thanks,
Doug
