[U-Boot] Loop Variable through to user space

[U-Boot] Loop Variable through to user space

[André Schaller]

Hi all,

during the execution of th MLO I create a variable, whose value I want
to make accessible to user space applications in Android. How can this
be achieved?

One way would be to write the contents of the variable to external
memory and let it read by the user space process. However, I would need
to make sure that during boot no other process is overwriting the address.

Do you know of any other ways?

Best,
Andr?

[U-Boot] Loop Variable through to user space

[Albert ARIBAUD]

Hello Andr?,

On Tue, 03 Feb 2015 13:57:28 +0100, Andr? Schaller
<an.schall@googlemail.com> wrote:
> Hi all,
> 
> during the execution of th MLO I create a variable, whose value I want
> to make accessible to user space applications in Android. How can this
> be achieved?
> 
> One way would be to write the contents of the variable to external
> memory and let it read by the user space process. However, I would need
> to make sure that during boot no other process is overwriting the address.
> 
> Do you know of any other ways?

Kind of a hack, but maybe you could pass the value somehow through the
kernel boot parameters? I assume that a meaningless parameter does not
affect the kernel but can still be parsed from /proc/cmdline.

> Best,
> Andr?

Amicalement,
-- 
Albert.

[U-Boot] Loop Variable through to user space

[André Schaller]

Hello Albert,

thanks for the information. Do you mean to pass the value using an
environment variable to the boot parameter? How would I approach to set
up an environment variable in the SPL? Wouldn't it increase the memory
footprint such that the SPL wouldn't fit into SRAM anymore?

Best,
Andr?

Am 03.02.15 um 23:27 schrieb Albert ARIBAUD:
> Hello Andr?,
> 
> On Tue, 03 Feb 2015 13:57:28 +0100, Andr? Schaller
> <an.schall@googlemail.com> wrote:
>> Hi all,
>>
>> during the execution of th MLO I create a variable, whose value I want
>> to make accessible to user space applications in Android. How can this
>> be achieved?
>>
>> One way would be to write the contents of the variable to external
>> memory and let it read by the user space process. However, I would need
>> to make sure that during boot no other process is overwriting the address.
>>
>> Do you know of any other ways?
> 
> Kind of a hack, but maybe you could pass the value somehow through the
> kernel boot parameters? I assume that a meaningless parameter does not
> affect the kernel but can still be parsed from /proc/cmdline.
> 
>> Best,
>> Andr?
> 
> Amicalement,
> 

[U-Boot] Loop Variable through to user space

[Simon Glass]

Hi,

On 3 February 2015 at 05:57, Andr? Schaller <an.schall@googlemail.com> wrote:
> Hi all,
>
> during the execution of th MLO I create a variable, whose value I want
> to make accessible to user space applications in Android. How can this
> be achieved?
>
> One way would be to write the contents of the variable to external
> memory and let it read by the user space process. However, I would need
> to make sure that during boot no other process is overwriting the address.
>
> Do you know of any other ways?

You could add it to the device tree in ft_board_setup() or ft_system_setup().

Regards,
Simon