[PATCH] drm: Use named initializers for arrays of i2c_device_data

[PATCH] drm: Use named initializers for arrays of i2c_device_data

[Uwe Kleine-König (The Capable Hub)]

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 in the list
terminator.

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@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. (I didn't find a serial 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

[1] https://cheri-alliance.org/discover-cheri/
    https://lwn.net/Articles/1037974/

 drivers/tty/serial/max310x.c       |  8 ++++----
 drivers/tty/serial/sc16is7xx_i2c.c | 14 +++++++-------
 2 files changed, 11 insertions(+), 11 deletions(-)

diff --git a/drivers/tty/serial/max310x.c b/drivers/tty/serial/max310x.c
index ac7d3f197c3a..742b8c23bacf 100644
--- a/drivers/tty/serial/max310x.c
+++ b/drivers/tty/serial/max310x.c
@@ -1671,10 +1671,10 @@ static void max310x_i2c_remove(struct i2c_client *client)
 }
 
 static const struct i2c_device_id max310x_i2c_id_table[] = {
-	{ "max3107",	(kernel_ulong_t)&max3107_devtype, },
-	{ "max3108",	(kernel_ulong_t)&max3108_devtype, },
-	{ "max3109",	(kernel_ulong_t)&max3109_devtype, },
-	{ "max14830",	(kernel_ulong_t)&max14830_devtype, },
+	{ .name = "max3107", .driver_data = (kernel_ulong_t)&max3107_devtype },
+	{ .name = "max3108", .driver_data = (kernel_ulong_t)&max3108_devtype },
+	{ .name = "max3109", .driver_data = (kernel_ulong_t)&max3109_devtype },
+	{ .name = "max14830", .driver_data = (kernel_ulong_t)&max14830_devtype },
 	{ }
 };
 MODULE_DEVICE_TABLE(i2c, max310x_i2c_id_table);
diff --git a/drivers/tty/serial/sc16is7xx_i2c.c b/drivers/tty/serial/sc16is7xx_i2c.c
index 699376c3b3a5..6c2a697556a6 100644
--- a/drivers/tty/serial/sc16is7xx_i2c.c
+++ b/drivers/tty/serial/sc16is7xx_i2c.c
@@ -39,13 +39,13 @@ static void sc16is7xx_i2c_remove(struct i2c_client *client)
 }
 
 static const struct i2c_device_id sc16is7xx_i2c_id_table[] = {
-	{ "sc16is74x",	(kernel_ulong_t)&sc16is74x_devtype, },
-	{ "sc16is740",	(kernel_ulong_t)&sc16is74x_devtype, },
-	{ "sc16is741",	(kernel_ulong_t)&sc16is74x_devtype, },
-	{ "sc16is750",	(kernel_ulong_t)&sc16is750_devtype, },
-	{ "sc16is752",	(kernel_ulong_t)&sc16is752_devtype, },
-	{ "sc16is760",	(kernel_ulong_t)&sc16is760_devtype, },
-	{ "sc16is762",	(kernel_ulong_t)&sc16is762_devtype, },
+	{ .name = "sc16is74x", .driver_data = (kernel_ulong_t)&sc16is74x_devtype },
+	{ .name = "sc16is740", .driver_data = (kernel_ulong_t)&sc16is74x_devtype },
+	{ .name = "sc16is741", .driver_data = (kernel_ulong_t)&sc16is74x_devtype },
+	{ .name = "sc16is750", .driver_data = (kernel_ulong_t)&sc16is750_devtype },
+	{ .name = "sc16is752", .driver_data = (kernel_ulong_t)&sc16is752_devtype },
+	{ .name = "sc16is760", .driver_data = (kernel_ulong_t)&sc16is760_devtype },
+	{ .name = "sc16is762", .driver_data = (kernel_ulong_t)&sc16is762_devtype },
 	{ }
 };
 MODULE_DEVICE_TABLE(i2c, sc16is7xx_i2c_id_table);

base-commit: 254f49634ee16a731174d2ae34bc50bd5f45e731
-- 
2.47.3

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

[Uwe Kleine-König (The Capable Hub)]

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Hello,

I messed up the Subject, of course this should have been:

	[PATCH] tty: serial: Use named initializers for arrays of i2c_device_data

please fix up accordingly iff you apply this version. If I should resend
for this reason, please tell me.

Best regards
Uwe

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

[Greg Kroah-Hartman]

On Mon, May 18, 2026 at 01:07:00PM +0200, Uwe Kleine-König (The Capable Hub) wrote:
> Hello,
> 
> I messed up the Subject, of course this should have been:
> 
> 	[PATCH] tty: serial: Use named initializers for arrays of i2c_device_data
> 
> please fix up accordingly iff you apply this version. If I should resend
> for this reason, please tell me.

I'll fix it up.

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

[Uwe Kleine-König (The Capable Hub)]

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On Fri, May 22, 2026 at 11:41:48AM +0200, Greg Kroah-Hartman wrote:
> On Mon, May 18, 2026 at 01:07:00PM +0200, Uwe Kleine-König (The Capable Hub) wrote:
> > Hello,
> > 
> > I messed up the Subject, of course this should have been:
> > 
> > 	[PATCH] tty: serial: Use named initializers for arrays of i2c_device_data
> > 
> > please fix up accordingly iff you apply this version. If I should resend
> > for this reason, please tell me.
> 
> I'll fix it up.

I see the fixup made it into the automatic notification that you picked
up the patch, so that worked fine. Thanks!

Uwe

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