[PATCH] Pass barebox version to kernel

[PATCH] Pass barebox version to kernel

[Sascha Hauer]

When userspace is interested in the barebox version it has currently no
way of reliably reading it. Add it to the kernel command line as it's an
established way to pass information from the bootloader to the kernel.
If CONFIG_FLEXIBLE_BOOTARGS is enabled then the barebox version is
passed in the "bootloader.version=" variable.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
---
 common/globalvar.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/common/globalvar.c b/common/globalvar.c
index b9bfce7dac..eff4cbc72e 100644
--- a/common/globalvar.c
+++ b/common/globalvar.c
@@ -571,6 +571,8 @@ int globalvar_add_simple_ip(const char *name, IPaddr_t *ip)
 	return 0;
 }
 
+static char *kernel_arg_bootloader_version;
+
 static int globalvar_init(void)
 {
 	register_device(&global_device);
@@ -580,6 +582,13 @@ static int globalvar_init(void)
 
 	globalvar_add_simple("version", UTS_RELEASE);
 
+	if (IS_ENABLED(CONFIG_FLEXIBLE_BOOTARGS)) {
+		kernel_arg_bootloader_version = basprintf("bootloader.version=barebox-%s",
+					       UTS_RELEASE);
+		globalvar_add_simple_string("linux.bootargs.bootloader.version",
+					    &kernel_arg_bootloader_version);
+	}
+
 	return 0;
 }
 pure_initcall(globalvar_init);
-- 
2.16.1


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Re: [PATCH] Pass barebox version to kernel

[Peter Mamonov]

Hi, Sasha,

On Mon, Feb 26, 2018 at 09:23:49AM +0100, Sascha Hauer wrote:
> When userspace is interested in the barebox version it has currently no
> way of reliably reading it. Add it to the kernel command line as it's an
> established way to pass information from the bootloader to the kernel.
> If CONFIG_FLEXIBLE_BOOTARGS is enabled then the barebox version is
> passed in the "bootloader.version=" variable.

Some time ago we solved a similar problem: a number of parameters including 
barebox version, MAC address (which may be random due to the lack of a NIC 
EEPROM) and some vendor specific parameters are passed to the kernel via DTB.  
A dedicated command was implemented which can either patch the existing DTB or 
generate an overlay DTB.  In the latter case the overlay DTB is passed to the 
kernel with the help of a new `bootm` option. Of course the latter approach 
requires support on the kernel side.

Are you interested in adopting this code into barebox?

Regards,
Peter

> 
> Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
> ---
>  common/globalvar.c | 9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> diff --git a/common/globalvar.c b/common/globalvar.c
> index b9bfce7dac..eff4cbc72e 100644
> --- a/common/globalvar.c
> +++ b/common/globalvar.c
> @@ -571,6 +571,8 @@ int globalvar_add_simple_ip(const char *name, IPaddr_t *ip)
>  	return 0;
>  }
>  
> +static char *kernel_arg_bootloader_version;
> +
>  static int globalvar_init(void)
>  {
>  	register_device(&global_device);
> @@ -580,6 +582,13 @@ static int globalvar_init(void)
>  
>  	globalvar_add_simple("version", UTS_RELEASE);
>  
> +	if (IS_ENABLED(CONFIG_FLEXIBLE_BOOTARGS)) {
> +		kernel_arg_bootloader_version = basprintf("bootloader.version=barebox-%s",
> +					       UTS_RELEASE);
> +		globalvar_add_simple_string("linux.bootargs.bootloader.version",
> +					    &kernel_arg_bootloader_version);
> +	}
> +
>  	return 0;
>  }
>  pure_initcall(globalvar_init);
> -- 
> 2.16.1
> 
> 
> _______________________________________________
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> barebox@lists.infradead.org
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Re: [PATCH] Pass barebox version to kernel

[Sascha Hauer]

Hi Peter,

On Mon, Feb 26, 2018 at 01:12:02PM +0300, Peter Mamonov wrote:
> Hi, Sasha,
> 
> On Mon, Feb 26, 2018 at 09:23:49AM +0100, Sascha Hauer wrote:
> > When userspace is interested in the barebox version it has currently no
> > way of reliably reading it. Add it to the kernel command line as it's an
> > established way to pass information from the bootloader to the kernel.
> > If CONFIG_FLEXIBLE_BOOTARGS is enabled then the barebox version is
> > passed in the "bootloader.version=" variable.
> 
> Some time ago we solved a similar problem: a number of parameters including 
> barebox version, MAC address (which may be random due to the lack of a NIC 
> EEPROM) and some vendor specific parameters are passed to the kernel via DTB.  
> A dedicated command was implemented which can either patch the existing DTB or 
> generate an overlay DTB.  In the latter case the overlay DTB is passed to the 
> kernel with the help of a new `bootm` option. Of course the latter approach 
> requires support on the kernel side.

We could of course pass the barebox version in the /chosen node. That
would require a of_register_fixup(). Why would we need an extra command
for that?
The MAC address should already be inserted into the kernel device tree
automatically.

Sascha

-- 
Pengutronix e.K.                           |                             |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |
Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0    |
Amtsgericht Hildesheim, HRA 2686           | Fax:   +49-5121-206917-5555 |

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Re: [PATCH] Pass barebox version to kernel

[Peter Mamonov]

On Tue, Feb 27, 2018 at 09:34:30AM +0100, Sascha Hauer wrote:
> Hi Peter,
> 
> On Mon, Feb 26, 2018 at 01:12:02PM +0300, Peter Mamonov wrote:
> > Hi, Sasha,
> > 
> > On Mon, Feb 26, 2018 at 09:23:49AM +0100, Sascha Hauer wrote:
> > > When userspace is interested in the barebox version it has currently no
> > > way of reliably reading it. Add it to the kernel command line as it's an
> > > established way to pass information from the bootloader to the kernel.
> > > If CONFIG_FLEXIBLE_BOOTARGS is enabled then the barebox version is
> > > passed in the "bootloader.version=" variable.
> > 
> > Some time ago we solved a similar problem: a number of parameters including 
> > barebox version, MAC address (which may be random due to the lack of a NIC 
> > EEPROM) and some vendor specific parameters are passed to the kernel via DTB.  
> > A dedicated command was implemented which can either patch the existing DTB or 
> > generate an overlay DTB.  In the latter case the overlay DTB is passed to the 
> > kernel with the help of a new `bootm` option. Of course the latter approach 
> > requires support on the kernel side.
> 
> We could of course pass the barebox version in the /chosen node. That
> would require a of_register_fixup(). Why would we need an extra command
> for that?

Well, it allows some extra flexibility: either original DTB is patched or a
separate DTB blob is generated. However there is no strict need for a command.

My actual point is that passing various bootloader stuff to a kernel via DTB
feels like a cleaner solution, rather than using kernel cmdline for that
purpose.

Regards,
Peter

> The MAC address should already be inserted into the kernel device tree
> automatically.
> 
> Sascha
> 
> -- 
> Pengutronix e.K.                           |                             |
> Industrial Linux Solutions                 | http://www.pengutronix.de/  |
> Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0    |
> Amtsgericht Hildesheim, HRA 2686           | Fax:   +49-5121-206917-5555 |

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Re: [PATCH] Pass barebox version to kernel

[Sascha Hauer]

On Tue, Feb 27, 2018 at 10:43:59PM +0300, Peter Mamonov wrote:
> On Tue, Feb 27, 2018 at 09:34:30AM +0100, Sascha Hauer wrote:
> > Hi Peter,
> > 
> > On Mon, Feb 26, 2018 at 01:12:02PM +0300, Peter Mamonov wrote:
> > > Hi, Sasha,
> > > 
> > > On Mon, Feb 26, 2018 at 09:23:49AM +0100, Sascha Hauer wrote:
> > > > When userspace is interested in the barebox version it has currently no
> > > > way of reliably reading it. Add it to the kernel command line as it's an
> > > > established way to pass information from the bootloader to the kernel.
> > > > If CONFIG_FLEXIBLE_BOOTARGS is enabled then the barebox version is
> > > > passed in the "bootloader.version=" variable.
> > > 
> > > Some time ago we solved a similar problem: a number of parameters including 
> > > barebox version, MAC address (which may be random due to the lack of a NIC 
> > > EEPROM) and some vendor specific parameters are passed to the kernel via DTB.  
> > > A dedicated command was implemented which can either patch the existing DTB or 
> > > generate an overlay DTB.  In the latter case the overlay DTB is passed to the 
> > > kernel with the help of a new `bootm` option. Of course the latter approach 
> > > requires support on the kernel side.
> > 
> > We could of course pass the barebox version in the /chosen node. That
> > would require a of_register_fixup(). Why would we need an extra command
> > for that?
> 
> Well, it allows some extra flexibility: either original DTB is patched or a
> separate DTB blob is generated. However there is no strict need for a command.
> 
> My actual point is that passing various bootloader stuff to a kernel via DTB
> feels like a cleaner solution, rather than using kernel cmdline for that
> purpose.

I tend to buy that argument. Especially when the stuff the bootloader
wants to pass becomes more and more then the device tree seems like a
good place. The downside is that not all boards have a devicetree (not
counting legacy boards here, but for example UEFI boards).

Any other opinions? We could also do both. If we only pass the version
then this would be ok I guess, but I have no idea where this leads to.

Sascha

-- 
Pengutronix e.K.                           |                             |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |
Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0    |
Amtsgericht Hildesheim, HRA 2686           | Fax:   +49-5121-206917-5555 |

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