[Linux-ia64] Simple Question Simple Answer

[Linux-ia64] Simple Question Simple Answer

[Brian Boerner]

Let me begin by saying that I'm not really new to Linux but have only
been doing Linux development for about a year now. I'm looking for a
list of differences one must consider when trying to write drivers that
are portable.

Correct me if I'm wrong, but the 2.2 code stream for Linux is ia32 while
the 2.4 code stream is going to support ia64. Is there a list of
gottchas somewhere that ISVs should watch out for? Please forgive me if
this is something that has been asked a 1000 times, but hey.. I'm new.

 -bmb-

Re: [Linux-ia64] Simple Question Simple Answer

[David Mosberger]

>>>>> On Mon, 13 Nov 2000 16:46:54 -0500, Brian Boerner <brian_boerner@ntc.adaptec.com> said:

  Brian> Correct me if I'm wrong, but the 2.2 code stream for Linux is
  Brian> ia32 while the 2.4 code stream is going to support ia64. Is
  Brian> there a list of gottchas somewhere that ISVs should watch out
  Brian> for? Please forgive me if this is something that has been
  Brian> asked a 1000 times, but hey.. I'm new.

It's not much, but there are some tips on porting to IA-64 Linux at:

 http://www.devresource.hp.com/devresource/Topics/IA64Linux/IA64Linux.html

Click on the "technical tips -> IA-64 Linux porting" link to get to
the right section.

	--david

Re: [Linux-ia64] Simple Question Simple Answer

[Jes Sorensen]

>>>>> "Brian" = Brian Boerner <brian_boerner@ntc.adaptec.com> writes:

Brian> Let me begin by saying that I'm not really new to Linux but
Brian> have only been doing Linux development for about a year
Brian> now. I'm looking for a list of differences one must consider
Brian> when trying to write drivers that are portable.

Brian> Correct me if I'm wrong, but the 2.2 code stream for Linux is
Brian> ia32 while the 2.4 code stream is going to support ia64. Is
Brian> there a list of gottchas somewhere that ISVs should watch out
Brian> for? Please forgive me if this is something that has been asked
Brian> a 1000 times, but hey.. I'm new.

That kinda depends on what you are trying to achieve. Are you trying
to write drivers that run under both 2.2 and 2.4 (covering all
applicaple architectures of course: little endian/big endian - 32 vs
64 bit) or just code that will run in 2.4?

There are some API changes which you have to deal with, but a lot of
that can be handled by putting in backwards compatibility macros for
2.2 in your code. I use that trick in the AceNIC Gigabit Ethernet
driver for instance (drivers/net/acenic.[ch]).

Jes

RE: [Linux-ia64] Simple Question Simple Answer

[Matt_Domsch]

Allow me to pass on some words of wisdom I received from Alan Cox a while
back.  Particularly for IA-64, the comment to use the new PCI DMA
architecture (linux/Documentatation/DMA-mapping.txt) has become especially
important, as >4GB systems will be fairly common, and many drivers I've seen
(as of September) were limiting system memory to 4GB because they hadn't
migrated to this yet.

Thanks,
Matt



   Alan Cox porting notes   6/12/2000 
The 2.2 to 2.4 porting should be easy. The big points are:

Remember to use pci_enable_device

dev->base_address[foo]. is now dev->resource[foo].start
and does not need masking for the flag bits

cli()/sti() type locking is now right out. In 2.2 its bad in 2.4 its
very very bad 8)

Use the new scsi error handling  - it really is a big win handling
degrading setups.

The scsi proc has changed

If its a PCI irq allocate using SA_SHIRQ but you must now pass
something other than NULL for the dev_id


If you want it to work on stuff like ia64 it needs to be both 64bit clean
and touch mmio space only using readb/readw/readl etc not by direct pointer
references.

If you want it to work with >4Gb of RAM you really want to use the new
pci_alloc_consistent API - but I would worry about that once it works
not before.

Alan