Re: CSMI questions

[Greg KH]

On Tue, Feb 22, 2005 at 11:16:56AM -0600, mikem wrote:
> All,
> I hate to dredge this up again, but, when Eric Moore submitted changes for MPT
> Fusion driver containing the CSMI ioctls it was rejected. There was talk on
> the linux-scsi list about it being a horrible interface, among other things.
> There were also comments about there being a Linux only approach. Personally,
> I like that idea but it's not good from a business perspective. Especially
> because HP, Dell, and others support more than one OS. Having a unique set of
> management apps for each OS would be very cumbersome.

Honestly, the kernel developers don't care about cross-OS platform
management utilities from a business perspective.  :)

> We've also been looking at how to use sysfs rather than ioctls.

Good.

> Some look reasonable, others seem to be restricted by sysfs itself. 
> 1. only ASCII files are allowed

With 1 value in that file.

> 2. if multiple attributes are contained in one file, who parses out the data?

multiple attributes are not allowed to be contained in a single file.

> 3. one buffer of size (PAGE_SIZE) may not hold all of the data required

You have a _single_ attribute that is bigger than PAGE_SIZE?  What is
it?

> I'd also like an (brief) explanation of why ioctls are so bad. I've seen the 
> reasons of them never going away, etc. But from the beginning of time (UNIX)
> ioctls have been the preferred method of user space/kernel communication.

That's because there was no other method.  See the lkml archives for why
ioctls are considered bad, I don't want to dredge it up again.

Hope this helps,

greg k-h
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