linux-kernel - Re: [PATCH] pci: show dma

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Message-ID: <20081023064412.GD31186@colo.lackof.org>
Date:	Thu, 23 Oct 2008 00:44:12 -0600
From:	Grant Grundler <grundler@...isc-linux.org>
To:	Matthew Wilcox <matthew@....cx>
Cc:	Yinghai Lu <yinghai@...nel.org>,
	Grant Grundler <grundler@...isc-linux.org>,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org
Subject: Re: [PATCH] pci: show dma_mask bits in /sys

On Wed, Oct 22, 2008 at 09:28:33PM -0600, Matthew Wilcox wrote:
> On Wed, Oct 22, 2008 at 06:45:10PM -0700, Yinghai Lu wrote:
> > Grant prefer to add it /sys instead of showing in bootlog
> > 
> > so could catch if the driver set the correct dma_mask.
> 
> I still don't think this is useful information to be exposing.

It's useful for anyone involved with device drivers - we agree that's
a very limited subset of users.  I certainly get fed up with trying
to figure out which dma_mask each driver is using since in some
cases it might vary depending on which HW is installed and which
kernel is running.

If the /sys patch added a PCI_DEBUG option to the kernel,
would that work for you?
I'm not keen on that but just looking for alternatives.
Many other subsystems (SCSI, ACPI, PM, HID, ...) have a FOO_DEBUG option.

Lastly, /sys seems to have over run even /proc. On an rx2600 (ia64):
grundler@...prf3:/usr/src/linux-2.6$ find /sys ! -type d | wc
   6288    6296  264893
grundler@...prf3:/usr/src/linux-2.6$ find /proc ! -type d | wc
find: `/proc/tty/driver': Permission denied
...
   4104    4104  100797

Pruning some of the crap out of there sounds like another task suitable for
"kernel janitor" project.
/me runs and hides :)

thanks,
grant
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