Re: [PATCH] leds: Use named initializers for arrays of i2c_device_data

From: Sverdlin, Alexander

Date: Mon May 18 2026 - 05:59:23 EST

Hi Uwe,

On Fri, 2026-05-15 at 18:33 +0200, Uwe Kleine-König (The Capable Hub) wrote:
> While being less compact, using named initializers allows to more easily
> see which members of the structs are assigned which value without having
> to lookup the declaration of the struct. And it's also more robust
> against changes to the struct definition.
>
> The mentioned robustness is relevant for a planned change to struct
> i2c_device_id that replaces .driver_data by an anonymous union.
>
> While touching all these arrays, unify usage of whitespace and commas.
>
> This patch doesn't modify the compiled arrays, only their representation
> in source form benefits. The former was confirmed with x86 and arm64
> builds.
>
> Signed-off-by: Uwe Kleine-König (The Capable Hub) <u.kleine-koenig@xxxxxxxxxxxx>

the patch looks good overall, except one minor nit below and the fact that
https://kernel.googlesource.com/pub/scm/linux/kernel/git/lee/leds for-leds-next
branch already has commit c7dd343a37567e650c263d4c068418b0bb82bf79
("leds: as3668: Driver for the ams Osram 4-channel i2c LED driver"), which is
not converted. Would it make sense to rebase and convert as3668 driver as well?

> ---
> Hello,
>
> the mentioned change to i2c_device_id is the following:
>
> diff --git a/include/linux/mod_devicetable.h b/include/linux/mod_devicetable.h
> index 23ff24080dfd..aebd3a5e90af 100644
> --- a/include/linux/mod_devicetable.h
> +++ b/include/linux/mod_devicetable.h
> @@ -477,7 +477,11 @@ struct rpmsg_device_id {
>
> struct i2c_device_id {
> char name[I2C_NAME_SIZE];
> - kernel_ulong_t driver_data; /* Data private to the driver */
> + union {
> + /* Data private to the driver */
> + kernel_ulong_t driver_data;
> + const void *driver_data_ptr;
> + };
> };
>
> /* pci_epf */
>
> and this requires that .driver_data is assigned via a named initializer
> for static data. This requirement isn't a bad one because named
> initializers are also much better readable than list initializers.
>
> The union added to struct i2c_device_id enables further cleanups like:
>
> diff --git a/drivers/regulator/ad5398.c b/drivers/regulator/ad5398.c
> index 0123ca8157a8..dfb0b07500a7 100644
> --- a/drivers/regulator/ad5398.c
> +++ b/drivers/regulator/ad5398.c
> @@ -207,8 +207,8 @@ struct ad5398_current_data_format {
> static const struct ad5398_current_data_format df_10_4_120 = {10, 4, 0, 120000};
>
> static const struct i2c_device_id ad5398_id[] = {
> - { .name = "ad5398", .driver_data = (kernel_ulong_t)&df_10_4_120 },
> - { .name = "ad5821", .driver_data = (kernel_ulong_t)&df_10_4_120 },
> + { .name = "ad5398", .driver_data_ptr = &df_10_4_120 },
> + { .name = "ad5821", .driver_data_ptr = &df_10_4_120 },
> { }
> };
> MODULE_DEVICE_TABLE(i2c, ad5398_id);
> @@ -219,8 +219,7 @@ static int ad5398_probe(struct i2c_client *client)
> struct regulator_init_data *init_data = dev_get_platdata(&client->dev);
> struct regulator_config config = { };
> struct ad5398_chip_info *chip;
> - const struct ad5398_current_data_format *df =
> - (struct ad5398_current_data_format *)id->driver_data;
> + const struct ad5398_current_data_format *df = id->driver_data;
>
> chip = devm_kzalloc(&client->dev, sizeof(*chip), GFP_KERNEL);
> if (!chip)
>
> that are an improvement for readability (again!) and it keeps some
> properties of the pointers (here: being const) without having to pay
> attention for that. (I didn't find a nice led driver that benefits, so
> this is "only" a regulator driver example.)
>
> My additional motivation for this effort is CHERI[1]. This is a hardware
> extension that uses 128 bit pointers but unsigned long is still 64 bit.
> So with CHERI you cannot store pointers in unsigned long variables.
>
> Best regards
> Uwe
>
> drivers/leds/flash/leds-as3645a.c | 2 +-
> drivers/leds/flash/leds-lm3601x.c | 4 ++--
> drivers/leds/leds-an30259a.c | 2 +-
> drivers/leds/leds-aw200xx.c | 10 +++++-----
> drivers/leds/leds-bd2802.c | 2 +-
> drivers/leds/leds-blinkm.c | 4 ++--
> drivers/leds/leds-is31fl319x.c | 22 +++++++++++-----------
> drivers/leds/leds-is31fl32xx.c | 18 +++++++++---------
> drivers/leds/leds-lm3530.c | 4 ++--
> drivers/leds/leds-lm3532.c | 4 ++--
> drivers/leds/leds-lm355x.c | 6 +++---
> drivers/leds/leds-lm3642.c | 4 ++--
> drivers/leds/leds-lm3692x.c | 4 ++--
> drivers/leds/leds-lm3697.c | 2 +-
> drivers/leds/leds-lp3944.c | 4 ++--
> drivers/leds/leds-lp3952.c | 4 ++--
> drivers/leds/leds-lp50xx.c | 12 ++++++------
> drivers/leds/leds-lp5521.c | 2 +-
> drivers/leds/leds-lp5523.c | 4 ++--
> drivers/leds/leds-lp5562.c | 2 +-
> drivers/leds/leds-lp5569.c | 2 +-
> drivers/leds/leds-lp8501.c | 2 +-
> drivers/leds/leds-lp8860.c | 2 +-
> drivers/leds/leds-lp8864.c | 4 ++--
> drivers/leds/leds-pca9532.c | 8 ++++----
> drivers/leds/leds-pca955x.c | 12 ++++++------
> drivers/leds/leds-pca963x.c | 8 ++++----
> drivers/leds/leds-pca995x.c | 8 ++++----
> drivers/leds/leds-st1202.c | 2 +-
> drivers/leds/leds-tca6507.c | 2 +-
> drivers/leds/leds-tlc591xx.c | 6 +++---
> drivers/leds/leds-turris-omnia.c | 2 +-
> drivers/leds/rgb/leds-ktd202x.c | 6 +++---
> 33 files changed, 90 insertions(+), 90 deletions(-)

[]

> diff --git a/drivers/leds/leds-lp8501.c b/drivers/leds/leds-lp8501.c
> index ee4ff4586bc0..946c27fd74cc 100644
> --- a/drivers/leds/leds-lp8501.c
> +++ b/drivers/leds/leds-lp8501.c
> @@ -130,7 +130,7 @@ static struct lp55xx_device_config lp8501_cfg = {
> };
>
> static const struct i2c_device_id lp8501_id[] = {
> - { "lp8501", .driver_data = (kernel_ulong_t)&lp8501_cfg, },
> + { .name = "lp8501", .driver_data = (kernel_ulong_t)&lp8501_cfg },
^^
duplicate whitespace

> { }
> };
> MODULE_DEVICE_TABLE(i2c, lp8501_id);

[]

> base-commit: 254f49634ee16a731174d2ae34bc50bd5f45e731

--
Alexander Sverdlin
Siemens AG
www.siemens.com