Re: linux-next: kbuild tree build failure

In-Reply-To: [off-list ref]

On Fri Jul 11 00:59:25 EST 2008, Roman Zippel wrote:

On Thu, 10 Jul 2008, Michael Ellerman wrote:

quoted

Well yes :)  But I think that's because you're thinking of
"end-users" and I'm thinking of "users" like myself - ie. _I_ use
Kconfig and I do expect myself to be able to type a 64-bit address.

That doesn't really answer my question, why you need this.

quoted

quoted

quoted

--- .config.orig  2008-07-08 09:30:00.000000000 +1000
+++ .config       2008-07-08 09:30:43.000000000 +1000

@@ -370,9 +370,8 @@
 CONFIG_HOTPLUG_PCI_RPA=m
 CONFIG_HOTPLUG_PCI_RPA_DLPAR=m
 # CONFIG_HAS_RAPIDIO is not set
-CONFIG_PAGE_OFFSET=0xc000000000000000
-CONFIG_KERNEL_START=0xc000000002000000
-CONFIG_PHYSICAL_START=0x02000000
+CONFIG_PAGE_OFFSET=0xc0000000
+CONFIG_PHYSICAL_START=0x2000000

Why is this worse? These are constants, you're not supposed to 

change them

quoted

quoted

anyway.
The remaining values are generated in page.h and should be the 

same as

quoted

quoted

before. If that isn't the case and this patch produces a nonworking
kernel, I'd like to hear about it.

You're right the built kernel is fine. So it's not a bug,

But its horrible code.

Good, could someone please ack whether the powerpc changes are 
acceptable?

Well, since no one else has said it,
NAK

The primary reason I object is this:

quoted

quoted

quoted

Index: linux-2.6/include/asm-powerpc/page.h
===================================================================

--- linux-2.6.orig/include/asm-powerpc/page.h
+++ linux-2.6/include/asm-powerpc/page.h

@@ -67,9 +67,15 @@
  * If you want to test if something's a kernel address, use 

is_kernel_addr().
  */

-#define KERNELBASE      ASM_CONST(CONFIG_KERNEL_START)
+#ifdef CONFIG_PPC64
+#define PAGE_OFFSET    (ASM_CONST(CONFIG_PAGE_OFFSET) << 32)
+#define KERNELBASE     
(PAGE_OFFSET+ASM_CONST(CONFIG_PHYSICAL_START))
+#define LOAD_OFFSET    PAGE_OFFSET
+#else
+#define KERNELBASE     ASM_CONST(CONFIG_KERNEL_START)
 #define PAGE_OFFSET    ASM_CONST(CONFIG_PAGE_OFFSET)
-#define LOAD_OFFSET    
ASM_CONST((CONFIG_KERNEL_START-CONFIG_PHYSICAL_START))
+#define LOAD_OFFSET    
(ASM_CONST(CONFIG_KERNEL_START)-ASM_CONST(CONFIG_PHYSICAL_START))
+#endif

 #if defined(CONFIG_RELOCATABLE) && defined(CONFIG_FLATMEM)
 #ifndef __ASSEMBLY__

(1) #define PAGE_OFFSET    (ASM_CONST(CONFIG_PAGE_OFFSET) << 32)

It creates unreadable code, where two defines with almost the same name 
(the only difference being
the CONFIG_ prefix, which is often ignored when scanning) contains 
radically different values.

(2)  #define PAGE_OFFSET    ASM_CONST(CONFIG_PAGE_OFFSET)

It creates config variables that mean different things depending on 
other config variables
The 32 and 64 bit powerpc kernel share a common source, a config 
variable should be used for
only one purpose.

quoted

but I think it is nicer to have the real values in the .config.

Why?

Mostly consistency between the different portions of the archticture.

As I remember, this code was adjusted and some of the defines moved 
from page.h
as part of the 32 bit relocatable kernel for 85xx booke ASMP support.

The 32 bit kernel has advanced options to change the VMA split, which 
enable
direct user input when explicitly defined.  That allows us to not need 
patches
for the embedded boards who need some other split than 3G/1G.  So there
is the reason that we have this directly specified in Kconfig at all.

While the 64 bit kernel doesn't need to actually change the page 
offset, as we
don't support the full 64 bits of the real address anyways (in fact, the
archtiecture prevents us from doing so) and therefore don't need to 
adjust
the effective address spilt between user and kernel.

But introducing config variables that mean different things is 
UNMAINTAINABLE.

Also, I remember, CONFIG_PAGE_OFFSET is used by the linker script and 
previously
page.h was conditionally included.   Does it always include page.h now?



On a seperate note,

quoted

quoted

quoted

 config PINT3_ASSIGN
        hex "PINT3_ASSIGN"
        depends on PINTx_REASSIGN
-       default 0x02020303
+       default 0x2020303

is harder to read.   The value is a list of 4 1 byte values, but you 
have hidden the first nibble making parsing the rest of the value hard.

quoted

quoted

quoted

 config IRAM_SIZE
        hex "Internal memory size (hex)"
        depends on (CHIP_M32700 || CHIP_M32102 || CHIP_VDEC2 || 
CHIP_OPSP || CHIP_M32104) && DISCONTIGMEM
-       default "00080000" if CHIP_M32700
-       default "00010000" if CHIP_M32102 || CHIP_OPSP || 
CHIP_M32104
-       default "00008000" if CHIP_VDEC2
+       default "0x80000" if CHIP_M32700
+       default "0x10000" if CHIP_M32102 || CHIP_OPSP || CHIP_M32104
+       default "0x8000" if CHIP_VDEC2

Likewize, I find it easier to mentally check the order of magnitude and 
compare sizes when they have
leading zeros and are right aligned.


Going to another email in the thread,

On Fri Jul 11 00:52:25 EST 2008, Roman Zippel wrpte:

On Tue, 8 Jul 2008, Sam Ravnborg wrote:

quoted

We use Kconfig for a mixture of user editable values and fixed
configuration values.
And I agree that asking the user to input a 64 bit number is not 

usefull.

quoted

But keeping support for 64 bit values is what I would consider
expected functionality.

...

quoted

quoted

This would also ease on any portability issues
(kconfig is compiled with the host compiler not the target 

compiler).

quoted

We use strtol() in a few places in symbol.c already where we do an
implicit conversion to int. Why did this not cause us problems 

before?

quoted

Is it because these code paths are only triggered when we deal with 

ranges?

quoted

If so we could 'fix' strdup_type() to not use strto{,u}l() so it
is 64 bit clean and we are back to old behaviour.

Ranges are the primary reason I made it consistent with this.
If we really wanted to support 64bit numbers, it would create only more
problems. First you have to make sure that on every build host (i.e 
also
non-Linux) strtoll() is available. Then how it should these numbers be
represented? On 32bit these may need a 'll' postfix, but the powerpc
example already shows, that there are different requirements, so they 
use
ASM_CONST for that. How should this postprecessing be integrated into
kconfig?

I think the architectures will already do something like ASM_CONST in
their C code when its needed.  This should not be the responsibility of
kbuild.

If you are worried about users tring to set values that are too high,
then make the types be hex8, hex16, hex32, and hex64.

milton

Hi,

On Sat, 12 Jul 2008, Milton Miller wrote:

(1) #define PAGE_OFFSET    (ASM_CONST(CONFIG_PAGE_OFFSET) << 32)

It creates unreadable code, where two defines with almost the same name (the
only difference being
the CONFIG_ prefix, which is often ignored when scanning) contains radically
different values.

(2)  #define PAGE_OFFSET    ASM_CONST(CONFIG_PAGE_OFFSET)

Giving it different names is not really difficult. Any objections to 
CONFIG_PAGE_HIGH_OFFSET?

On a seperate note,

quoted

quoted

quoted

quoted

 config PINT3_ASSIGN
        hex "PINT3_ASSIGN"
        depends on PINTx_REASSIGN
-       default 0x02020303
+       default 0x2020303

is harder to read.   The value is a list of 4 1 byte values, but you have
hidden the first nibble making parsing the rest of the value hard.

Sam mentioned that already, but that's a situation where the warning can 
be relaxed.

If you are worried about users tring to set values that are too high,
then make the types be hex8, hex16, hex32, and hex64.

It's not this, I value consistency as much as you and the values are 
sometimes used as integers, so a working range is needed. Using simple 
integers keeps things much simpler and as the ASM_CONST example shows any 
bigger values are not necessarily directly usable anyway.

bye, Roman