On Fri, 02 May 2025, Ming Yu wrote:

Lee Jones [off-list ref] 於 2025年5月2日 週五 下午4:08寫道：

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+static const struct mfd_cell nct6694_devs[] = {
+     MFD_CELL_BASIC("nct6694-gpio", NULL, NULL, 0, 0),
+     MFD_CELL_BASIC("nct6694-gpio", NULL, NULL, 0, 1),
+     MFD_CELL_BASIC("nct6694-gpio", NULL, NULL, 0, 2),
+     MFD_CELL_BASIC("nct6694-gpio", NULL, NULL, 0, 3),
+     MFD_CELL_BASIC("nct6694-gpio", NULL, NULL, 0, 4),
+     MFD_CELL_BASIC("nct6694-gpio", NULL, NULL, 0, 5),
+     MFD_CELL_BASIC("nct6694-gpio", NULL, NULL, 0, 6),
+     MFD_CELL_BASIC("nct6694-gpio", NULL, NULL, 0, 7),
+     MFD_CELL_BASIC("nct6694-gpio", NULL, NULL, 0, 8),
+     MFD_CELL_BASIC("nct6694-gpio", NULL, NULL, 0, 9),
+     MFD_CELL_BASIC("nct6694-gpio", NULL, NULL, 0, 10),
+     MFD_CELL_BASIC("nct6694-gpio", NULL, NULL, 0, 11),
+     MFD_CELL_BASIC("nct6694-gpio", NULL, NULL, 0, 12),
+     MFD_CELL_BASIC("nct6694-gpio", NULL, NULL, 0, 13),
+     MFD_CELL_BASIC("nct6694-gpio", NULL, NULL, 0, 14),
+     MFD_CELL_BASIC("nct6694-gpio", NULL, NULL, 0, 15),

These are all identical.

I thought you were going to use PLATFORM_DEVID_AUTO?  In fact, you are
already using PLATFORM_DEVID_AUTO since you are calling
mfd_add_hotplug_devices().  So you don't need this IDs.

MFD_CELL_NAME() should do.

Yes, it uses PLATFORM_DEVID_AUTO, but in my implementation, the
sub-devices use cell->id instead of platform_device->id, so it doesn't
affect the current behavior.
However, if you think there's a better approach or that this should be
changed for consistency or correctness, I'm happy to update it, please
let me know your recommendation.

When using MFD_CELL_NAME(), the platform_device->id for the GPIO
devices is assigned values from 1 to 16, and for the I2C devices from
1 to 6, but I need the ID offset to start from 0 instead.

Oh no, don't do that.  mfd_cell isn't supposed to be used outside of MFD.

Just use the platform_device id-- if you really need to start from 0.

As an aside, I'm surprised numbering starts from 1.

OK, I will use platform_device->id instead. However, I'm still unsure
why the ID starts from1.

Additionally, I noticed that when calling mfd_add_devices()
separately, the IDs are also assigned consecutively (e.g., GPIO: 1~16,
I2C: 17~22, ...).

Do you have any recommendations on how I should implement this?

If you are to use this mechanism, you'd have to submit separate
mfd_add_devices() calls I guess.

However, this all seems a bit silly for simple, contextless (where
device 3 is identical to device 10, etc) enumeration.  Can you use IDA
instead?

-- 
Lee Jones [李琼斯]