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[209.85.167.43]) by smtp.gmail.com with ESMTPSA id q27sm434478lfo.242.2020.11.20.10.59.49 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 20 Nov 2020 10:59:50 -0800 (PST) Received: by mail-lf1-f43.google.com with SMTP id u19so14930867lfr.7 for ; Fri, 20 Nov 2020 10:59:49 -0800 (PST) X-Received: by 2002:a19:4b92:: with SMTP id y140mr8175542lfa.485.1605898789139; Fri, 20 Nov 2020 10:59:49 -0800 (PST) MIME-Version: 1.0 References: <20201118234025.376412-1-evgreen@chromium.org> <20201118153951.RESEND.v3.2.Idef164c23d326f5e5edecfc5d3eb2a68fcf18be1@changeid> In-Reply-To: From: Evan Green Date: Fri, 20 Nov 2020 10:59:12 -0800 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [RESEND PATCH v3 2/2] i2c: i2c-mux-gpio: Enable this driver in ACPI land To: Andy Shevchenko Cc: Peter Rosin , Wolfram Sang , Randy Dunlap , Peter Korsgaard , linux-i2c , Linux Kernel Mailing List Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-i2c@vger.kernel.org On Thu, Nov 19, 2020 at 7:24 AM Andy Shevchenko wrote: > > On Thu, Nov 19, 2020 at 1:40 AM Evan Green wrote: > > > > Enable i2c-mux-gpio devices to be defined via ACPI. The idle-state > > property translates directly to a fwnode_property_*() call. The child > > reg property translates naturally into _ADR in ACPI. > > > > The i2c-parent binding is a relic from the days when the bindings > > dictated that all direct children of an I2C controller had to be I2C > > devices. These days that's no longer required. The i2c-mux can sit as a > > direct child of its parent controller, which is where it makes the most > > sense from a hardware description perspective. For the ACPI > > implementation we'll assume that's always how the i2c-mux-gpio is > > instantiated. > > ... > > > +#ifdef CONFIG_ACPI > > + > > +static int i2c_mux_gpio_get_acpi_adr(struct device *dev, > > + struct fwnode_handle *fwdev, > > + unsigned int *adr) > > + > > +{ > > + unsigned long long adr64; > > + acpi_status status; > > + > > + status = acpi_evaluate_integer(ACPI_HANDLE_FWNODE(fwdev), > > + METHOD_NAME__ADR, > > + NULL, &adr64); > > + > > + if (!ACPI_SUCCESS(status)) { > > + dev_err(dev, "Cannot get address\n"); > > + return -EINVAL; > > + } > > + > > + *adr = adr64; > > + if (*adr != adr64) { > > + dev_err(dev, "Address out of range\n"); > > + return -ERANGE; > > + } > > + > > + return 0; > > +} > > + > > +#else > > + > > +static int i2c_mux_gpio_get_acpi_adr(struct device *dev, > > + struct fwnode_handle *fwdev, > > + unsigned int *adr) > > +{ > > + return -EINVAL; > > +} > > + > > +#endif > > I'm wondering if you may use acpi_find_child_device() here. > Or is it a complementary function? I think it's complementary. The code above is "I have a device, I want its _ADR". whereas acpi_find_child_device() is "I have an _ADR, I want its device". I could flip things around to use this, but it would turn the code from linear into quadratic. I'd have to scan each possible address and call acpi_find_child_device() with that _ADR to see if there's a child device there. > > ... > > > + device_for_each_child_node(dev, child) { > > + if (is_of_node(child)) { > > + fwnode_property_read_u32(child, "reg", values + i); > > + > > + } else if (is_acpi_node(child)) { > > + rc = i2c_mux_gpio_get_acpi_adr(dev, child, values + i); > > + if (rc) > > + return rc; > > + } > > + > > i++; > > } > > And for this I already told in two different threads with similar code > that perhaps we need common helper that will check reg followed by > _ADR. Oh, I'm not aware of those threads. I'd need some advice: I guess a new fwnode_* API would make sense for this, but I had trouble coming up with a generic interface. _ADR is just a blobbo 64 bit int, but DT's "reg" is a little more flexible, having a length, and potentially being an array. I suppose it would have to be something like: int fwnode_property_read_reg(const struct fwnode_handle *fwnode, size_t index, uint64_t *addr, uint64_t *len); But then ACPI would always return 0 for length, and only index 0 would ever work? I'm worried I'm designing an API that's only useful to me. I tried to look around for other examples of this specific pattern of _ADR then "reg", but struggled to turn up much. -Evan > > -- > With Best Regards, > Andy Shevchenko