* [U-Boot] u-boot environment variable parsing
@ 2011-07-21 8:28 Hebbar, Gururaja
2011-07-21 13:11 ` Wolfgang Denk
0 siblings, 1 reply; 3+ messages in thread
From: Hebbar, Gururaja @ 2011-07-21 8:28 UTC (permalink / raw)
To: u-boot
Hi,
I need one clarification regarding Environment variable declaration & its usage.
#define CONFIG_EXTRA_ENV_SETTINGS \
"brd_mem=62M\0" \
"bootargs_defaults=setenv bootargs " \
"console=${console} " \
"mem=${brd_mem}\0" \
"mmc_args=run bootargs_defaults;" \
"setenv bootargs $(bootargs) " \
"root=${mmc_root} " \
"rootfstype=${mmc_root_fs_type} ip=${ip_method}\0" \
"nand_args=run bootargs_defaults;" \
"setenv bootargs ${bootargs} " \
"root=${nand_root} noinitrd " \
"rootfstype=${nand_root_fs_type} ip=${ip_method}\0" \
The question here is mmc_args re-uses variable bootargs as $(bootargs) & nand_args re-uses it as ${bootargs}. Note the difference in curly & flower brackets. "run mmc_args" fails for me however nand_args runs properly.
My question is
1. Which is correct?
2. What is the difference between the two?
I have seen few boards using both methods.
Thanks in advance
Regards
Gururaja
^ permalink raw reply [flat|nested] 3+ messages in thread
* [U-Boot] u-boot environment variable parsing
2011-07-21 8:28 [U-Boot] u-boot environment variable parsing Hebbar, Gururaja
@ 2011-07-21 13:11 ` Wolfgang Denk
2011-07-22 10:49 ` Hebbar, Gururaja
0 siblings, 1 reply; 3+ messages in thread
From: Wolfgang Denk @ 2011-07-21 13:11 UTC (permalink / raw)
To: u-boot
Dear "Hebbar, Gururaja",
In message <C82BA3053CFD354AACBD25EFBD2A4EC603F0193C2D@dbde02.ent.ti.com> you wrote:
>
>
> The question here is mmc_args re-uses variable bootargs as
> $(bootargs) & nand_args re-uses it as ${bootargs}. Note the
> difference in curly & flower brackets. "run mmc_args" fails for me
> however nand_args runs properly.
Does this not answer your question sufficiently?
> My question is
> 1. Which is correct?
${...} is correct.
> 2. What is the difference between the two?
${...} is correct, and $(...) is not correct.
> I have seen few boards using both methods.
$(...) was used in very old versions of U-Boot, but this got changed
for the sake of compatibility with standard shell syntax.
Note that the simple cmmand line parser still accepts the obsolete
$(...) format; the hush shell doesn't.
Best regards,
Wolfgang Denk
--
DENX Software Engineering GmbH, MD: Wolfgang Denk & Detlev Zundel
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
A morsel of genuine history is a thing so rare as to be always
valuable. - Thomas Jefferson
^ permalink raw reply [flat|nested] 3+ messages in thread
* [U-Boot] u-boot environment variable parsing
2011-07-21 13:11 ` Wolfgang Denk
@ 2011-07-22 10:49 ` Hebbar, Gururaja
0 siblings, 0 replies; 3+ messages in thread
From: Hebbar, Gururaja @ 2011-07-22 10:49 UTC (permalink / raw)
To: u-boot
Hi wd,
Thanks for the reply. Helped me a lot.
However see below
On Thu, Jul 21, 2011 at 18:41:30, Wolfgang Denk wrote:
> Dear "Hebbar, Gururaja",
>
> In message <C82BA3053CFD354AACBD25EFBD2A4EC603F0193C2D@dbde02.ent.ti.com> you wrote:
> >
> >
> > The question here is mmc_args re-uses variable bootargs as
> > $(bootargs) & nand_args re-uses it as ${bootargs}. Note the difference
> > in curly & flower brackets. "run mmc_args" fails for me however
> > nand_args runs properly.
>
> Does this not answer your question sufficiently?
The point is mmc_args worked in one place & failed in other. After you reply, I found that the place where it worked was common shell environment & it was failing in Hush shell.
>
> > My question is
> > 1. Which is correct?
>
> ${...} is correct.
>
> > 2. What is the difference between the two?
>
> ${...} is correct, and $(...) is not correct.
>
> > I have seen few boards using both methods.
>
> $(...) was used in very old versions of U-Boot, but this got changed for the sake of compatibility with standard shell syntax.
>
> Note that the simple cmmand line parser still accepts the obsolete
> $(...) format; the hush shell doesn't.
>
> Best regards,
>
> Wolfgang Denk
>
> --
> DENX Software Engineering GmbH, MD: Wolfgang Denk & Detlev Zundel
> HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
> Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de A morsel of genuine history is a thing so rare as to be always
> valuable. - Thomas Jefferson
>
Regards,
Gururaja
^ permalink raw reply [flat|nested] 3+ messages in thread
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2011-07-21 8:28 [U-Boot] u-boot environment variable parsing Hebbar, Gururaja
2011-07-21 13:11 ` Wolfgang Denk
2011-07-22 10:49 ` Hebbar, Gururaja
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