[U-Boot] Sandbox question

[Mike Frysinger]

On Monday 23 April 2012 17:17:57 Wolfgang Denk wrote:
> Mike Frysinger wrote:
> > also, what you're proposing is changing the behavior of u-boot when it's
> > in the sandbox so that it acts less like the hardware.  when you run
> > u-boot on the hardware and it's sitting at the prompt, u-boot is running
> > the cpu at 100%.
> 
> Correct.  But then U-Boot is the only master of the CPU, and nothing
> else can be run in parallel.
> 
> In the sandbox, U-Boot is an ordinary user space application and as
> such is supposed to behave well.  Burning 100% CPU is a polling input
> loop is about the most stupid thing we can do.

not when you're aiming to act like the hardware whenever possible.  we 
specifically do not want #ifdef CONFIG_SANDBOX outside of sandbox-specific 
drivers if we can avoid it.  that means we are bound by the implicit 
constraints at the driver boundaries.  so if u-boot common code does:
	while (tstc())
		...
then sandbox should be eating the cpu.  however, it seems that the hush shell 
does while (getc()), so that shouldn't be an issue here.

> > > Why invent new methods when we can encapsulate this in the input
> > > interface?
> > 
> > i'm not inventing new methods.  i'm telling you that the sandbox OS layer
> > today cannot access the C library's errno because u-boot's own
> > implementation of errno is overriding it.  so any call sandbox makes to
> > the OS (like read() or select() or poll()) that results in an error,
> > sandbox has no way of knowing the underlying reason.
> 
> Than this needs to be fixed for sandbox?

the only way to fix it is what i suggested: rename "int errno" in lib/errno.c 
to something like "int uboot_errno" and then add to errno.h: "#define errno 
uboot_errno".  this shouldn't make any difference at all to compiled code.  the 
only difference is that people doing symbol debugging would get a different 
symbol name.
-mike
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