[PATCH 1/1] i2c: align i2c_device_id

[PATCH 1/1] i2c: align i2c_device_id

[Jiri Slaby]

Align i2c_device_id.driver_data to 8 bytes to not fail on crossbuilds.

(Added in d2653e92732bd3911feff6bee5e23dbf959381db.)

Signed-off-by: Jiri Slaby <jirislaby-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
Cc: Jean Delvare <khali-PUYAD+kWke1g9hUCZPvPmw@public.gmane.org>
---
 include/linux/mod_devicetable.h |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/include/linux/mod_devicetable.h b/include/linux/mod_devicetable.h
index a37db57..1fd03e7 100644
--- a/include/linux/mod_devicetable.h
+++ b/include/linux/mod_devicetable.h
@@ -384,7 +384,8 @@ struct virtio_device_id {
 
 struct i2c_device_id {
 	char name[I2C_NAME_SIZE];
-	kernel_ulong_t driver_data;	/* Data private to the driver */
+	kernel_ulong_t driver_data	/* Data private to the driver */
+			__attribute__((aligned(sizeof(kernel_ulong_t))));
 };
 
 
-- 
1.5.4.5


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Re: [PATCH 1/1] i2c: align i2c_device_id

[Sam Ravnborg]

On Mon, May 19, 2008 at 03:18:44PM +0200, Jiri Slaby wrote:
> Align i2c_device_id.driver_data to 8 bytes to not fail on crossbuilds.
> 
> (Added in d2653e92732bd3911feff6bee5e23dbf959381db.)
> 
> Signed-off-by: Jiri Slaby <jirislaby-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
> Cc: Jean Delvare <khali-PUYAD+kWke1g9hUCZPvPmw@public.gmane.org>
> ---
>  include/linux/mod_devicetable.h |    3 ++-
>  1 files changed, 2 insertions(+), 1 deletions(-)
> 
> diff --git a/include/linux/mod_devicetable.h b/include/linux/mod_devicetable.h
> index a37db57..1fd03e7 100644
> --- a/include/linux/mod_devicetable.h
> +++ b/include/linux/mod_devicetable.h
> @@ -384,7 +384,8 @@ struct virtio_device_id {
>  
>  struct i2c_device_id {
>  	char name[I2C_NAME_SIZE];
> -	kernel_ulong_t driver_data;	/* Data private to the driver */
> +	kernel_ulong_t driver_data	/* Data private to the driver */
> +			__attribute__((aligned(sizeof(kernel_ulong_t))));
>  };

Thanks Jiri.

	Sam

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Re: [PATCH 1/1] i2c: align i2c_device_id

[Jean Delvare]

Hi Jiri,

On Mon, 19 May 2008 15:18:44 +0200, Jiri Slaby wrote:
> Align i2c_device_id.driver_data to 8 bytes to not fail on crossbuilds.
> 
> (Added in d2653e92732bd3911feff6bee5e23dbf959381db.)
> 
> Signed-off-by: Jiri Slaby <jirislaby@gmail.com>
> Cc: Jean Delvare <khali@linux-fr.org>
> ---
>  include/linux/mod_devicetable.h |    3 ++-
>  1 files changed, 2 insertions(+), 1 deletions(-)
> 
> diff --git a/include/linux/mod_devicetable.h b/include/linux/mod_devicetable.h
> index a37db57..1fd03e7 100644
> --- a/include/linux/mod_devicetable.h
> +++ b/include/linux/mod_devicetable.h
> @@ -384,7 +384,8 @@ struct virtio_device_id {
>  
>  struct i2c_device_id {
>  	char name[I2C_NAME_SIZE];
> -	kernel_ulong_t driver_data;	/* Data private to the driver */
> +	kernel_ulong_t driver_data	/* Data private to the driver */
> +			__attribute__((aligned(sizeof(kernel_ulong_t))));
>  };
>  

Thanks for this patch, it's in my i2c tree now and will be sent to
Linus by the end of the week. I wasn't aware of this possible alignment
issue, sorry.

-- 
Jean Delvare

Re: [PATCH 1/1] i2c: align i2c_device_id

[Jiri Slaby]

On 05/19/2008 09:00 PM, Jean Delvare wrote:
> Hi Jiri,

Hi.

> Thanks for this patch, it's in my i2c tree now and will be sent to
> Linus by the end of the week. I wasn't aware of this possible alignment
> issue, sorry.

To be honest, neither I was until I hit it while testing hid bus (where I did 
the same mistake). Thanks.

Re: [i2c] [PATCH 1/1] i2c: align i2c_device_id

[Trent Piepho]

On Mon, 19 May 2008, Jiri Slaby wrote:
> On 05/19/2008 09:00 PM, Jean Delvare wrote:
> > Thanks for this patch, it's in my i2c tree now and will be sent to
> > Linus by the end of the week. I wasn't aware of this possible alignment
> > issue, sorry.
>
> To be honest, neither I was until I hit it while testing hid bus (where I did
> the same mistake). Thanks.

Is there any more information about this?  Items in a structure should be
aligned to the alignment required by their type.  Usually sizeof(x) ==
alignof(x), but not always.

I guess in this case the structures are used as a cross-platform binary on
disk representation, and so the alignment of the build host must match the
alignment of the target?

Maybe it would be better to include the alignment attribute in the
definition of kernel_ulong_t?