[PATCH] i2c: i2c-boardinfo: Annotate code used in init phase only

[PATCH] i2c: i2c-boardinfo: Annotate code used in init phase only

[Heiner Kallweit]

Annotate two places in boardinfo code:
- __i2c_first_dynamic_bus_num is set in init phase. Annotate it as
  __ro_after_init to prevent later changes.
- i2c_register_board_info() is used in init phase only, so annotate it
  as __init, allowing to free the memory after init phase.
  This is safe, see comment: "done in board-specific init code near
  arch_initcall() time"

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
---
 drivers/i2c/i2c-boardinfo.c | 4 ++--
 include/linux/i2c.h         | 2 +-
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/i2c/i2c-boardinfo.c b/drivers/i2c/i2c-boardinfo.c
index 4df8ad092..338800321 100644
--- a/drivers/i2c/i2c-boardinfo.c
+++ b/drivers/i2c/i2c-boardinfo.c
@@ -22,7 +22,7 @@ EXPORT_SYMBOL_GPL(__i2c_board_lock);
 LIST_HEAD(__i2c_board_list);
 EXPORT_SYMBOL_GPL(__i2c_board_list);
 
-int __i2c_first_dynamic_bus_num;
+int __i2c_first_dynamic_bus_num __ro_after_init;
 EXPORT_SYMBOL_GPL(__i2c_first_dynamic_bus_num);
 
 
@@ -48,7 +48,7 @@ EXPORT_SYMBOL_GPL(__i2c_first_dynamic_bus_num);
  * The board info passed can safely be __initdata, but be careful of embedded
  * pointers (for platform_data, functions, etc) since that won't be copied.
  */
-int i2c_register_board_info(int busnum, struct i2c_board_info const *info, unsigned len)
+int __init i2c_register_board_info(int busnum, struct i2c_board_info const *info, unsigned len)
 {
 	int status;
 
diff --git a/include/linux/i2c.h b/include/linux/i2c.h
index 20fd41b51..11a19241e 100644
--- a/include/linux/i2c.h
+++ b/include/linux/i2c.h
@@ -499,7 +499,7 @@ static inline struct i2c_client *i2c_verify_client(struct device *dev)
  * Modules for add-on boards must use other calls.
  */
 #ifdef CONFIG_I2C_BOARDINFO
-int
+int __init
 i2c_register_board_info(int busnum, struct i2c_board_info const *info,
 			unsigned n);
 #else
-- 
2.51.0

Re: [PATCH] i2c: i2c-boardinfo: Annotate code used in init phase only

[Wolfram Sang]

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On Sun, Sep 14, 2025 at 10:24:13PM +0200, Heiner Kallweit wrote:
> Annotate two places in boardinfo code:
> - __i2c_first_dynamic_bus_num is set in init phase. Annotate it as
>   __ro_after_init to prevent later changes.
> - i2c_register_board_info() is used in init phase only, so annotate it
>   as __init, allowing to free the memory after init phase.
>   This is safe, see comment: "done in board-specific init code near
>   arch_initcall() time"
> 
> Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>

Applied to for-next, thanks!

The other patch needs some more time to look at.


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Re: [PATCH] i2c: i2c-boardinfo: Annotate code used in init phase only

[Konrad Dybcio]

On 9/14/25 10:24 PM, Heiner Kallweit wrote:
> Annotate two places in boardinfo code:
> - __i2c_first_dynamic_bus_num is set in init phase. Annotate it as
>   __ro_after_init to prevent later changes.
> - i2c_register_board_info() is used in init phase only, so annotate it
>   as __init, allowing to free the memory after init phase.
>   This is safe, see comment: "done in board-specific init code near
>   arch_initcall() time"
> 
> Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
> ---

Hi, this seems to break booting on Qualcomm X1E80100 Surface Laptop 7
(arm64/boot/dts/qcom/x1e80100-microsoft-romulus.dtsi)

gcc-14.2 and clang-20.x

Funnily enough when I build this (albeit on another computer, but also
with clang-20.x) and boot another X1E80100-based device (x1-crd.dtsi
in the same DT dir), it boots up fine

Konrad

Re: [PATCH] i2c: i2c-boardinfo: Annotate code used in init phase only

[Wolfram Sang]

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Hi Konrad,

> Hi, this seems to break booting on Qualcomm X1E80100 Surface Laptop 7
> (arm64/boot/dts/qcom/x1e80100-microsoft-romulus.dtsi)
> 
> gcc-14.2 and clang-20.x
> 
> Funnily enough when I build this (albeit on another computer, but also
> with clang-20.x) and boot another X1E80100-based device (x1-crd.dtsi
> in the same DT dir), it boots up fine

I reverted the commit now, but please if you can find out more details
about the boot regression, this would be extremly helpful (maybe
earlycon helps?).

All the best,

   Wolfram


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Re: [PATCH] i2c: i2c-boardinfo: Annotate code used in init phase only

[Konrad Dybcio]

On 10/11/25 12:33 PM, Wolfram Sang wrote:
> Hi Konrad,
> 
>> Hi, this seems to break booting on Qualcomm X1E80100 Surface Laptop 7
>> (arm64/boot/dts/qcom/x1e80100-microsoft-romulus.dtsi)
>>
>> gcc-14.2 and clang-20.x
>>
>> Funnily enough when I build this (albeit on another computer, but also
>> with clang-20.x) and boot another X1E80100-based device (x1-crd.dtsi
>> in the same DT dir), it boots up fine
> 
> I reverted the commit now, but please if you can find out more details
> about the boot regression, this would be extremly helpful (maybe
> earlycon helps?).

I'll try to poke at it the upcoming week, thanks

Konrad

Re: [PATCH] i2c: i2c-boardinfo: Annotate code used in init phase only

[Heiner Kallweit]

On 10/10/2025 9:50 PM, Konrad Dybcio wrote:
> On 9/14/25 10:24 PM, Heiner Kallweit wrote:
>> Annotate two places in boardinfo code:
>> - __i2c_first_dynamic_bus_num is set in init phase. Annotate it as
>>   __ro_after_init to prevent later changes.
>> - i2c_register_board_info() is used in init phase only, so annotate it
>>   as __init, allowing to free the memory after init phase.
>>   This is safe, see comment: "done in board-specific init code near
>>   arch_initcall() time"
>>
>> Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
>> ---
> 
> Hi, this seems to break booting on Qualcomm X1E80100 Surface Laptop 7
> (arm64/boot/dts/qcom/x1e80100-microsoft-romulus.dtsi)
> 
What means "seems to break"? Is it or not? Did you bisect?
Where exactly does the boot break/stop?
Can you provide a full dmesg log for success and error case on this device?


> gcc-14.2 and clang-20.x
> 
> Funnily enough when I build this (albeit on another computer, but also
> with clang-20.x) and boot another X1E80100-based device (x1-crd.dtsi
> in the same DT dir), it boots up fine
> 
> Konrad

Re: [PATCH] i2c: i2c-boardinfo: Annotate code used in init phase only

[Heiner Kallweit]

On 10/11/2025 6:14 PM, Konrad Dybcio wrote:
> On 10/11/25 12:33 PM, Wolfram Sang wrote:
>> Hi Konrad,
>>
>>> Hi, this seems to break booting on Qualcomm X1E80100 Surface Laptop 7
>>> (arm64/boot/dts/qcom/x1e80100-microsoft-romulus.dtsi)
>>>
>>> gcc-14.2 and clang-20.x
>>>
>>> Funnily enough when I build this (albeit on another computer, but also
>>> with clang-20.x) and boot another X1E80100-based device (x1-crd.dtsi
>>> in the same DT dir), it boots up fine
>>
>> I reverted the commit now, but please if you can find out more details
>> about the boot regression, this would be extremly helpful (maybe
>> earlycon helps?).
> 
> I'll try to poke at it the upcoming week, thanks
> 
Any result? It's somewhat unfortunate to revert a change just because of a
vague report w/o evidence / logs / bisect results.

> Konrad