From: Michael Ellerman <michael@ellerman.id.au>
To: Jan-Bernd Themann <ossthema@de.ibm.com>
Cc: Thomas Klein <tklein@de.ibm.com>, netdev <netdev@vger.kernel.org>,
linux-kernel <linux-kernel@vger.kernel.org>,
linux-ppc <linuxppc-dev@ozlabs.org>,
Christoph Raisch <raisch@de.ibm.com>,
Marcus Eder <meder@de.ibm.com>
Subject: Re: [PATCH 4/6] ehea: header files
Date: Tue, 15 Aug 2006 10:08:19 +1000 [thread overview]
Message-ID: <1155600499.9047.13.camel@localhost.localdomain> (raw)
In-Reply-To: <44E07267.7070007@de.ibm.com>
[-- Attachment #1: Type: text/plain, Size: 2027 bytes --]
On Mon, 2006-08-14 at 14:53 +0200, Jan-Bernd Themann wrote:
> Michael Ellerman wrote:
> >> --- linux-2.6.18-rc4-orig/drivers/net/ehea/ehea.h 1969-12-31 16:00:00.000000000 -0800
> >> +++ kernel/drivers/net/ehea/ehea.h 2006-08-08 23:59:39.927452928 -0700
> >> +
> >> +#define EHEA_PAGESHIFT 12
> >> +#define EHEA_PAGESIZE 4096UL
> >> +#define EHEA_CACHE_LINE 128
> >
> > This looks like a very bad idea, what happens if you're running on a
> > machine with 64K pages?
> >
>
> The EHEA_PAGESIZE define is needed for queue management to hardware side.
You mean the eHEA has its own concept of page size? Separate from the
page size used by the MMU?
> >> +/*
> >> + * h_galpa:
> >> + * for pSeries this is a 64bit memory address where
> >> + * I/O memory is mapped into CPU address space
> >> + */
> >> +
> >> +struct h_galpa {
> >> + u64 fw_handle;
> >> +};
> >
> > What is a h_galpa? And why does it need a struct if it's just a u64?
> >
>
> The eHEA chip is not PCI attached but directly connected to a proprietary
> bus. Currently, we can access it by a simple 64 bit address, but this is not
> true in all cases. Having a struct here allows us to encapsulate the chip
> register access and to respond to changes to system hardware.
>
> We'll change the name to h_epa meaning "ehea physical address"
Hmm, I'm not convinced. Having the struct doesn't really encapsulate
much, because most of the places where you use the h_galpa struct just
pull out the fw_handle anyway. So if you change the layout of the struct
you're going to have to change most of the code anyway. And in the
meantime it makes the code a lot less readable, most people understand
what "u64 addr" is about, whereas "struct h_galpa" is much less
meaningful. </2c>
cheers
--
Michael Ellerman
IBM OzLabs
wwweb: http://michael.ellerman.id.au
phone: +61 2 6212 1183 (tie line 70 21183)
We do not inherit the earth from our ancestors,
we borrow it from our children. - S.M.A.R.T Person
[-- Attachment #2: This is a digitally signed message part --]
[-- Type: application/pgp-signature, Size: 191 bytes --]
next prev parent reply other threads:[~2006-08-15 0:08 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-08-09 8:39 [PATCH 4/6] ehea: header files Jan-Bernd Themann
2006-08-09 13:17 ` Arnd Bergmann
2006-08-10 6:22 ` Michael Ellerman
2006-08-14 12:53 ` Jan-Bernd Themann
2006-08-15 0:08 ` Michael Ellerman [this message]
2006-08-15 9:44 ` Jan-Bernd Themann
2006-08-15 10:53 ` Jenkins, Clive
2006-08-15 11:07 ` Christoph Raisch
2006-08-15 11:09 ` edlk4.0 ppc_85xx gdb problems emre kara
2006-08-15 11:46 ` Jenkins, Clive
2006-08-16 0:58 ` [PATCH 4/6] ehea: header files Michael Ellerman
2006-08-11 21:40 ` Anton Blanchard
2006-08-14 3:20 ` Michael Ellerman
2006-08-14 6:19 ` Jan-Bernd Themann
2006-08-11 22:07 ` Anton Blanchard
2006-08-12 16:40 ` Thomas Klein
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=1155600499.9047.13.camel@localhost.localdomain \
--to=michael@ellerman.id.au \
--cc=linux-kernel@vger.kernel.org \
--cc=linuxppc-dev@ozlabs.org \
--cc=meder@de.ibm.com \
--cc=netdev@vger.kernel.org \
--cc=ossthema@de.ibm.com \
--cc=raisch@de.ibm.com \
--cc=tklein@de.ibm.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).