Re: [PATCH] [v2] Input: stmpe-ts - mark OF related data as maybe unused

["Arnd Bergmann" <arnd@arndb.de>]

On Tue, Feb 25, 2025, at 21:17, Uwe Kleine-König wrote:
> On Tue, Feb 25, 2025 at 05:25:05PM +0100, Arnd Bergmann wrote:
>> On Tue, Feb 25, 2025, at 16:47, Uwe Kleine-König wrote:
>> > On Tue, Feb 25, 2025 at 03:53:26PM +0100, Arnd Bergmann wrote:
>> > the warning goes away and stmpe_ts_ids isn't included in the .o file
>> > without having to add __maybe_unused to the driver.
>> >
>> > I would consider that a superior approach.
>> 
>> Not sure, I can see how this avoids some warnings, but this is
>> currently the only remaining instance of this problem (I fixed
>> another two recently), and in most cases a MODULE_DEVICE_TABLE()
>> entry that is completely unused ends up pointing to a real bug,
>> where there is a table but it's not also part of the
>> device_driver definition.
>
> It might be the only instance without __maybe_unused and so triggering a
> warning. But there is also:
>
> $ git grep -E 'of_device_id.*__maybe_unused' | wc -l
> 231
>
> $ git grep -E 'mdio_device_id.*__maybe_unused' | wc -l
> 58

I'm not really worried about these at the moment, other than not
wanting to pile on to that mess with more __maybe_unused
annotations.

My goal here is to get the point of enabling -Wunused-const-variable
by default in order to find other bugs before they make it into
the kernel.

Andy Shevchenko really wants to remove the of_match_ptr()
macro so we can stop adding pointless __maybe_unused annotations
for every driver that accidentally uses of_match_ptr(). This
is certainly a good idea as well, just not what I'm trying to
do this time.

Apparently we have already accumulated a bunch of drivers that
ended up with __maybe_unused but no actual reference from
of_match_ptr():

$ git grep -l 'of_device_id.*__maybe_unused' |xargs grep -Lw of_match_ptr | wc -l

but only a couple of drivers that don't use of_match_ptr()
or of_match_node():

$ git grep -l 'of_device_id.*__maybe_unused' |xargs grep -Lw 'of_match_table\|of_match_node'
drivers/cpufreq/armada-37xx-cpufreq.c
drivers/cpufreq/armada-8k-cpufreq.c
drivers/cpufreq/highbank-cpufreq.c
drivers/cpufreq/sti-cpufreq.c
drivers/hwmon/isl28022.c
drivers/input/touchscreen/stmpe-ts.c
drivers/mfd/twl6030-irq.c
drivers/tty/serial/sc16is7xx.c

I do think it makes sense to change of_match_node() to have a
reference to its arguments, as in the patch below. That
probably needs a few extra fixups.

     Arnd


diff --git a/include/linux/of.h b/include/linux/of.h
index 9d6b8a61607f..83cfa6c26ee4 100644
--- a/include/linux/of.h
+++ b/include/linux/of.h
@@ -907,7 +907,11 @@ static inline const void *of_device_get_match_data(const struct device *dev)
 }
 
 #define of_match_ptr(_ptr)	NULL
-#define of_match_node(_matches, _node)	NULL
+static inline const struct of_device_id *of_match_node(
+	const struct of_device_id *matches, const struct device_node *node)
+{
+	return NULL;
+}
 #endif /* CONFIG_OF */
 
 /* Default string compare functions, Allow arch asm/prom.h to override */
diff --git a/drivers/crypto/caam/ctrl.c b/drivers/crypto/caam/ctrl.c
index d4b39184dbdb..bd418dea586d 100644
--- a/drivers/crypto/caam/ctrl.c
+++ b/drivers/crypto/caam/ctrl.c
@@ -80,7 +80,6 @@ static void build_deinstantiation_desc(u32 *desc, int handle)
 	append_jump(desc, JUMP_CLASS_CLASS1 | JUMP_TYPE_HALT);
 }
 
-#ifdef CONFIG_OF
 static const struct of_device_id imx8m_machine_match[] = {
 	{ .compatible = "fsl,imx8mm", },
 	{ .compatible = "fsl,imx8mn", },
@@ -89,7 +88,6 @@ static const struct of_device_id imx8m_machine_match[] = {
 	{ .compatible = "fsl,imx8ulp", },
 	{ }
 };
-#endif
 
 /*
  * run_descriptor_deco0 - runs a descriptor on DECO0, under direct control of
diff --git a/drivers/dma/dw/rzn1-dmamux.c b/drivers/dma/dw/rzn1-dmamux.c
index 4fb8508419db..9dcba3a3ffaa 100644
--- a/drivers/dma/dw/rzn1-dmamux.c
+++ b/drivers/dma/dw/rzn1-dmamux.c
@@ -104,12 +104,10 @@ static void *rzn1_dmamux_route_allocate(struct of_phandle_args *dma_spec,
 	return ERR_PTR(ret);
 }
 
-#ifdef CONFIG_OF
 static const struct of_device_id rzn1_dmac_match[] = {
 	{ .compatible = "renesas,rzn1-dma" },
 	{}
 };
-#endif
 
 static int rzn1_dmamux_probe(struct platform_device *pdev)
 {
diff --git a/drivers/i2c/busses/i2c-at91-core.c b/drivers/i2c/busses/i2c-at91-core.c
index edc047e3e535..3a9be06dd967 100644
--- a/drivers/i2c/busses/i2c-at91-core.c
+++ b/drivers/i2c/busses/i2c-at91-core.c
@@ -108,7 +108,6 @@ static const struct platform_device_id at91_twi_devtypes[] = {
 	}
 };
 
-#if defined(CONFIG_OF)
 static struct at91_twi_pdata at91sam9x5_config = {
 	.clk_max_div = 7,
 	.clk_offset = 4,
@@ -178,7 +177,6 @@ static const struct of_device_id atmel_twi_dt_ids[] = {
 	}
 };
 MODULE_DEVICE_TABLE(of, atmel_twi_dt_ids);
-#endif
 
 static struct at91_twi_pdata *at91_twi_get_driver_data(
 					struct platform_device *pdev)
diff --git a/drivers/i2c/busses/i2c-xiic.c b/drivers/i2c/busses/i2c-xiic.c
index dc1e46d834dc..969e08e4d4f4 100644
--- a/drivers/i2c/busses/i2c-xiic.c
+++ b/drivers/i2c/busses/i2c-xiic.c
@@ -1409,7 +1409,6 @@ static const struct i2c_adapter xiic_adapter = {
 	.algo = &xiic_algorithm,
 };
 
-#if defined(CONFIG_OF)
 static const struct xiic_version_data xiic_2_00 = {
 	.quirks = DYNAMIC_MODE_READ_BROKEN_BIT,
 };
@@ -1420,7 +1419,6 @@ static const struct of_device_id xiic_of_match[] = {
 	{},
 };
 MODULE_DEVICE_TABLE(of, xiic_of_match);
-#endif
 
 static int xiic_i2c_probe(struct platform_device *pdev)
 {
diff --git a/drivers/misc/atmel-ssc.c b/drivers/misc/atmel-ssc.c
index 35a196341534..3db592f3b451 100644
--- a/drivers/misc/atmel-ssc.c
+++ b/drivers/misc/atmel-ssc.c
@@ -111,7 +111,6 @@ static const struct platform_device_id atmel_ssc_devtypes[] = {
 	}
 };
 
-#ifdef CONFIG_OF
 static const struct of_device_id atmel_ssc_dt_ids[] = {
 	{
 		.compatible = "atmel,at91rm9200-ssc",
@@ -127,7 +126,6 @@ static const struct of_device_id atmel_ssc_dt_ids[] = {
 	}
 };
 MODULE_DEVICE_TABLE(of, atmel_ssc_dt_ids);
-#endif
 
 static inline const struct atmel_ssc_platform_data *
 	atmel_ssc_get_driver_data(struct platform_device *pdev)
diff --git a/drivers/net/can/at91_can.c b/drivers/net/can/at91_can.c
index 191707d7e3da..9fbbf3587b0c 100644
--- a/drivers/net/can/at91_can.c
+++ b/drivers/net/can/at91_can.c
@@ -1013,7 +1013,6 @@ static const struct attribute_group at91_sysfs_attr_group = {
 	.attrs = at91_sysfs_attrs,
 };
 
-#if defined(CONFIG_OF)
 static const struct of_device_id at91_can_dt_ids[] = {
 	{
 		.compatible = "atmel,at91sam9x5-can",
@@ -1026,7 +1025,6 @@ static const struct of_device_id at91_can_dt_ids[] = {
 	}
 };
 MODULE_DEVICE_TABLE(of, at91_can_dt_ids);
-#endif
 
 static const struct at91_devtype_data *at91_can_get_driver_data(struct platform_device *pdev)
 {
diff --git a/drivers/net/ethernet/cadence/macb_main.c b/drivers/net/ethernet/cadence/macb_main.c
index 6c462de81f20..f942c6e54a1b 100644
--- a/drivers/net/ethernet/cadence/macb_main.c
+++ b/drivers/net/ethernet/cadence/macb_main.c
@@ -4425,7 +4425,6 @@ static const struct macb_usrio_config macb_default_usrio = {
 	.refclk = MACB_BIT(CLKEN),
 };
 
-#if defined(CONFIG_OF)
 /* 1518 rounded up */
 #define AT91ETHER_MAX_RBUFF_SZ	0x600
 /* max number of receive buffers */
@@ -5144,7 +5143,6 @@ static const struct of_device_id macb_dt_ids[] = {
 	{ /* sentinel */ }
 };
 MODULE_DEVICE_TABLE(of, macb_dt_ids);
-#endif /* CONFIG_OF */
 
 static const struct macb_config default_gem_config = {
 	.caps = MACB_CAPS_GIGABIT_MODE_AVAILABLE |