Messages in this thread | | | Subject | Re: [PATCH 1/2] drivers: base: swnode: link devices to software nodes | From | "Rafael J. Wysocki" <> | Date | Tue, 30 Jul 2019 16:49:50 +0200 |
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On 7/30/2019 1:52 PM, Heikki Krogerus wrote: > On Mon, Jul 29, 2019 at 03:15:32PM +0200, Dmitry Torokhov wrote: >> On Mon, Jul 29, 2019 at 03:07:15PM +0300, Heikki Krogerus wrote: >>> On Sat, Jul 13, 2019 at 12:52:58AM -0700, Dmitry Torokhov wrote: >>>> It is helpful to know what device, if any, a software node is tied to, so >>>> let's store a pointer to the device in software node structure. Note that >>>> children software nodes will inherit their parent's device pointer, so we >>>> do not have to traverse hierarchy to see what device the [sub]tree belongs >>>> to. >>>> >>>> We will be using the device pointer to locate GPIO lookup tables for >>>> devices with static properties. >>>> >>>> Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com> >>>> --- >>>> drivers/base/property.c | 1 + >>>> drivers/base/swnode.c | 35 ++++++++++++++++++++++++++++++++++- >>>> include/linux/property.h | 5 +++++ >>>> 3 files changed, 40 insertions(+), 1 deletion(-) >>>> >>>> diff --git a/drivers/base/property.c b/drivers/base/property.c >>>> index 348b37e64944..3bc93d4b35c4 100644 >>>> --- a/drivers/base/property.c >>>> +++ b/drivers/base/property.c >>>> @@ -527,6 +527,7 @@ int device_add_properties(struct device *dev, >>>> if (IS_ERR(fwnode)) >>>> return PTR_ERR(fwnode); >>>> >>>> + software_node_link_device(fwnode, dev); >>>> set_secondary_fwnode(dev, fwnode); >>>> return 0; >>>> } >>>> diff --git a/drivers/base/swnode.c b/drivers/base/swnode.c >>>> index 7fc5a18e02ad..fd12eea539b6 100644 >>>> --- a/drivers/base/swnode.c >>>> +++ b/drivers/base/swnode.c >>>> @@ -24,6 +24,9 @@ struct software_node { >>>> >>>> /* properties */ >>>> const struct property_entry *properties; >>>> + >>>> + /* device this node is associated with */ >>>> + struct device *dev; >>>> }; >>> Let's not do that! The nodes can be, and in many cases are, associated >>> with multiple devices. >> They do? Where? I see that set of properties can be shared between >> several devices, but when we instantiate SW node we create a new >> instance for device. This is also how ACPI and OF properties work; they >> not shared between devices (or, rather, the kernel creates distinct _and >> single_ devices for instance of ACPI or OF node). I do not think we want >> swnodes work differently from the other firmware nodes. > Having multiple devices linked to a single node is quite normal. Most > multifunctional devices will share a single node. The USB port devices > will share their node (if they have one) with any device that is > attached to them. Etc. > > If you want to check how this works with ACPI, then find > "physical_node" named files from sysfs. The ACPI node folders in sysfs > have symlinks named "physical_node<n>" for every device they are bind > to. The first one is named just "physical_node", the second > "physical_node1", the third "physical_node2", and so on. > >>> Every device is already linked with the software node kobject, so >>> isn't it possible to simply walk trough those links in order to check >>> the devices associated with the node? >> No, we need to know the exact instance of a device, not a set of >> devices, because even though some properties can be shared, others can >> not. For example, even if 2 exactly same touch controllers in the system >> have "reset-gpios" property, they won't be the same GPIO for the both of >> them. > I don't think I completely understand the use case you had in mind for > this API, but since you planned to use it with the GPIO lookup tables, > I'm going to assume it's not needed after all. Let's replace those > with the references instead like I proposed in my reply to the 2/2 > patch. > > Linking a single device with a node like that is in any case not > acceptable nor possible. > I think I need to withdraw my ACK here at this point.
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