On Friday, September 26, 2014 10:36:06 AM Arnd Bergmann wrote: > On Thursday 25 September 2014 20:21:32 Darren Hart wrote: > > On Wed, Sep 24, 2014 at 11:12:36AM +0200, Arnd Bergmann wrote: > > > How would you feel about a more general way of probing LED, using > > > a new helper in the leds-core that iterates over the child nodes > > > and parses the standard properties but calls into a driver specific > > > callback to parse the specific properties? > > > It's probably much more work than your current approach, but it seems > > > to me that there is more to gain by solving the problem for LED > > > drivers in particular to cut down the per-driver duplication > > > at the same time as the per-firmware-interface duplication. > > > > > > As a start, we could probably take the proposed device_for_each_child_node > > > and move that into the leds-core, changing the fw_dev_node argument > > > for an led_classdev with the addition of the of_node and acpi_object > > > members. It would still leave it up to the gpio-leds driver to do > > > > > > if (led_cdev->of_node) > > > gpiod = devm_of_get_gpiod(led_cdev->of_node, ...); > > > else > > > gpiod = devm_acpi_get_gpiod(led_cdev->acpi_object, ...); > > > > So as Mika has pointed out, LEDs aren't the only ones affected. Several drivers > > will need to walk through non-device child nodes, and it seems to me that having > > a firmware-independent mechanism to do so benefits the drivers by both making > > them smaller and by increasing the reusability of new drivers and drivers > > updated to use the new API across platforms. > > > > I fear we might be entering bike shed territory as we seem to be repeating > > points now. Can you restate your concern with the interface and why this level > > of abstraction is worse for the kernel? I'm not seeing this point, so I'm not > > sure what to address in my response. > > I think we should have abstractions for all common interfaces but make > them as simple as possible. In the discussions at the kernel summit, > everyone agreed that we should have common accessors for simple properties > (bool, int, string, ...) based on device pointers, as well as subsystem > specific accessors to handle the high-level abstractions (registers, > interrupts, gpio, regulator, pinctrl, dma, reset, pwm, ...). > > Having generalized accessors for the same properties in child nodes of > the device goes beyond that, and I think this is the wrong trade-off > between interface simplicity and generality since only few drivers will > be able to use those. I think we will always have to live with a leaky > abstraction because some drivers need to do things beyond what we can > do with a common API. Some drivers do, but then we can avoid adding DT/ACPI knowledge to some drivers by adding general accessors for properties in child nodes. In my opinion, drivers should not do things specific to DT/ACPI unless that is unavoidable. > > > Grant, Linus W? Thoughts? > > I definitely want to hear other voices on this too. This is really not > a fundamental debate I think, but more a question of how far the abstraction > should go. Right. -- I speak only for myself. Rafael J. Wysocki, Intel Open Source Technology Center. -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
