[PATCH v1] regulator: Use named initializers for arrays of i2c_device_data
Laurent Pinchart
laurent.pinchart at ideasonboard.com
Fri May 15 05:28:16 PDT 2026
Hi Uwe,
Thank you for the patch.
On Fri, May 15, 2026 at 12:31:50PM +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 at baylibre.com>
> ---
> 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.
>
> 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
>
> [1] https://cheri-alliance.org/discover-cheri/
> https://lwn.net/Articles/1037974/
>
> drivers/regulator/88pg86x.c | 4 +--
> drivers/regulator/ad5398.c | 4 +--
> drivers/regulator/da9121-regulator.c | 20 +++++++--------
> drivers/regulator/da9210-regulator.c | 4 +--
> drivers/regulator/da9211-regulator.c | 18 +++++++-------
> drivers/regulator/fan53880.c | 4 +--
> drivers/regulator/isl9305.c | 4 +--
> drivers/regulator/lp3971.c | 2 +-
> drivers/regulator/lp3972.c | 2 +-
> drivers/regulator/lp872x.c | 34 +++++++++++++-------------
> drivers/regulator/lp8755.c | 4 +--
> drivers/regulator/ltc3589.c | 6 ++---
> drivers/regulator/ltc3676.c | 2 +-
> drivers/regulator/max1586.c | 2 +-
> drivers/regulator/max20086-regulator.c | 8 +++---
> drivers/regulator/max20411-regulator.c | 2 +-
> drivers/regulator/max77503-regulator.c | 2 +-
> drivers/regulator/max77675-regulator.c | 2 +-
> drivers/regulator/max77826-regulator.c | 2 +-
> drivers/regulator/max77838-regulator.c | 2 +-
> drivers/regulator/max77857-regulator.c | 8 +++---
> drivers/regulator/max8649.c | 2 +-
> drivers/regulator/max8893.c | 2 +-
> drivers/regulator/max8952.c | 2 +-
> drivers/regulator/mcp16502.c | 2 +-
> drivers/regulator/mp5416.c | 6 ++---
> drivers/regulator/mp8859.c | 4 +--
> drivers/regulator/mp886x.c | 6 ++---
> drivers/regulator/mpq7920.c | 4 +--
> drivers/regulator/mt6311-regulator.c | 4 +--
> drivers/regulator/pf530x-regulator.c | 8 +++---
> drivers/regulator/pf8x00-regulator.c | 8 +++---
> drivers/regulator/pv88060-regulator.c | 4 +--
> drivers/regulator/pv88080-regulator.c | 8 +++---
> drivers/regulator/pv88090-regulator.c | 4 +--
> drivers/regulator/slg51000-regulator.c | 4 +--
> drivers/regulator/sy8106a-regulator.c | 2 +-
> drivers/regulator/sy8824x.c | 8 +++---
> drivers/regulator/sy8827n.c | 4 +--
> drivers/regulator/tps6286x-regulator.c | 10 ++++----
> drivers/regulator/tps6287x-regulator.c | 10 ++++----
> 41 files changed, 119 insertions(+), 119 deletions(-)
[snip]
> diff --git a/drivers/regulator/pf530x-regulator.c b/drivers/regulator/pf530x-regulator.c
> index f789c4b6a499..e7b13d60106b 100644
> --- a/drivers/regulator/pf530x-regulator.c
> +++ b/drivers/regulator/pf530x-regulator.c
> @@ -353,10 +353,10 @@ static const struct of_device_id pf530x_dt_ids[] = {
> MODULE_DEVICE_TABLE(of, pf530x_dt_ids);
>
> static const struct i2c_device_id pf530x_i2c_id[] = {
> - { "pf5300", 0 },
> - { "pf5301", 0 },
> - { "pf5302", 0 },
> - {},
> + { .name = "pf5300", .driver_data = 0 },
> + { .name = "pf5301", .driver_data = 0 },
> + { .name = "pf5302", .driver_data = 0 },
I think you can drop driver_data here. It doesn't appear to be used by
the driver.
I like the result overall. With this small issue addressed,
Reviewed-by: Laurent Pinchart <laurent.pinchart+renesas at ideasonboard.com>
> + { }
> };
> MODULE_DEVICE_TABLE(i2c, pf530x_i2c_id);
>
[snip]
--
Regards,
Laurent Pinchart
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