Messages in this thread | | | Date | Wed, 24 Jun 2020 09:47:20 +0200 | From | Michael Walle <> | Subject | Re: [PATCH v2 1/3] mfd: core: Make a best effort attempt to match devices with the correct of_nodes |
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Hi,
Am 2020-06-24 08:41, schrieb Lee Jones: > On Tue, 23 Jun 2020, Frank Rowand wrote: > >> On 2020-06-11 14:10, Lee Jones wrote: >> > Currently, when a child platform device (sometimes referred to as a >> > sub-device) is registered via the Multi-Functional Device (MFD) API, >> > the framework attempts to match the newly registered platform device >> > with its associated Device Tree (OF) node. Until now, the device has >> > been allocated the first node found with an identical OF compatible >> > string. Unfortunately, if there are, say for example '3' devices >> > which are to be handled by the same driver and therefore have the same >> > compatible string, each of them will be allocated a pointer to the >> > *first* node. >> >> As you mentioned elsewhere in this thread, this series "fixes" the >> problem related to the "stericsson,ab8500-pwm" compatible. >> >> I know, I said I would drop discussion of that compatible, but bear >> with me for a second. :-) >> >> The "problem" is that the devices for multiple mfd child nodes with >> the same compatible value of "stericsson,ab8500-pwm" will all have >> a pointer to the first child node. At the moment the same child >> of_node being used by more than one device does not cause any >> incorrect behavior. >> >> Just in case the driver for "stericsson,ab8500-pwm" is modified >> in a way that the child of_node needs to be distinct for each >> device, and that changes gets back ported, it would be useful >> to have Fixes: tags for this patch series. >> >> So, at your discretion (and I'll let you worry about the correct >> Fixes: tag format), this series fixes: >> >> bad76991d7847b7877ae797cc79745d82ffd9120 mfd: Register ab8500 devices >> using the newly DT:ed MFD API > > This patch isn't actually broken. > > The issue is the DTB, which [0] addresses. > > [0] > https://lkml.kernel.org/lkml/20200622083432.1491715-1-lee.jones@linaro.org/
Now, I'm confused; because this patch doesn't use the reg property but a different node name. I'd actually prefer this for any MFD driver which has multiple nodes of the same compatible string. See my reasoning here [1]. But until now, no one has responded. Thus, I'd rather see a OF_MFD_CELL_NAME() which matches the node name instead of the OF_MFD_CELL_REG() macro.
This would also circumvent the fact that the unit-address has one number space. Eg. it is not possible to have:
mfd { compatible = "mfd,compatible";
gpio@0 { reg = <0>; }; gpio@1 { reg = <1>; }; pwm@0 { reg = <0>; }; };
Although Rob mentioned to maybe relax that, but I sill fail to see the advantage to have an arbitrary reg property instead of a unique node name.
[1] https://lore.kernel.org/linux-devicetree/0709f20bc61afb6656bc57312eb69f56@walle.cc/
-- -michael
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