Re: Choosing scatter/gather limits

[Pierre Ossman]

Russell King wrote:

> On Mon, Oct 11, 2004 at 12:53:23PM +0200, Pierre Ossman wrote:
>  
>
> > I've been adding scatter/gather support for the MMC host driver I'm 
> > writing. I cannot find any documentation on how to chose the limits though.
> >    
>
> It seems that you have to read the block layer code to find out what's
> going on with these limits.  There's some documentation on it in
> Documentation/block/bio.txt.  If it's lacking, then please send
> comments to the block layer people to add the necessary information.
>
>  
I just wanted to make sure I don't pick values that causes problems 
somewhere else. I'll make an attempt to dig through the bio code though.

> Please also note that I'm intending to make the MMC host drivers
> know nothing about block IO stuff, so all you'll be passed is the
> MMC commands and a scatter gather list - so making sure that your
> driver always uses blk_rq_map_sg() and works from the SG list will
> ensure that your driver remains easy to update.
>
>  
Shouldn't be a problem. The SGIO support in the driver is done. Just 
need to get rid of all bugs.

Rgds
Pierre


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