Re: sysfs abuse in recent i2o changes

[Greg KH <gregkh@suse.de>]

On Tue, Jun 28, 2005 at 08:08:20PM +0200, Markus Lidel wrote:
> Hello,
> 
> Greg KH wrote:
> >On Tue, Jun 28, 2005 at 05:02:41PM +0200, Markus Lidel wrote:
> >>I know, but i hopefully also have a good reason to do so... First, the 
> >>attributes provided through these functions are for accessing the 
> >>firmware... The controller has a little limitation, it could only handle 
> >>64 blocks, but sysfs only have 4k...
> >>Now there are two options:
> >>1) when writing: read a 64k block, merge it with the 4k block and write 
> >>it back, when reading: read a 64k block and only return the needed 4k 
> >>block.
> >>2) extend the sysfs attribute to allow 64k blocks
> >>IMHO the first is not a very good solution, because for a 64k block it 
> >>has to be written 16 times...
> >>Of course if someone finds a better solution i would be glad to hear 
> >>about it...
> >Use the binary file interface of sysfs, which was written exactly for
> >this kind of thing. :)
> 
> Oh i tried to use the binary interface, but i haven't found a way to 
> increase the block size beyond 4k, could you please tell me how i could 
> adjust it, or where i could read about it?
> 
> Thank you very much!

Your code should not care about the block size of the data given to you,
as userspace could be giving you 1 byte at a time.  Buffer it up
yourself and then write it out to the device when needed.

But if you are doing this for firmware, then please use the kernel
firmware interface, it does all of the buffering for you.

Either way, having your own file_ops in sysfs is not allowed.

thanks,

greg k-h