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@xxxxxxxxxx/
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@xxxxxxxx/
--
-michael
