Re: set blksize of block device

[Lei Yang]

Shesha B. Sreenivasamurthy wrote:

> Firstly you cannot set the block size to lesser than 512. 
>
> When there is a request for the IO, you populate "struct req" data
> structure which you will pass it to the kernel or lower level SCSI/SATA
> driver. In the "struct req" there is a field "b_size" which may be what
> you are interested in. At the user level you can use the IOCTLs to set
> the block size of the RAW block device.
>
> -Shesha
>  
I understand that for real block device (like hard disk), block size 
cannot be less than 512. But to ramdisks, I think they are truely random 
addressable, and should be able to move on blocks even with size of 2 bytes.

Any comments?

> On Wed, 2004-10-27 at 18:44, Lei Yang wrote:
>  
>
> > If nobody could answer this question, what about another one? Is there a 
> > system call or a kernel interface that would allow me to write a block 
> > of data to block 1 of a certain block device?
> >
> > Thanks for your reply in advance!
> >
> > Lei
> >
> > Lei Yang wrote:
> >
> >    
> >
> > > Please cc me if you have answers to this, I am not on the list. Thanks 
> > > a lot!
> > >
> > > Lei Yang wrote:
> > >
> > >      
> > >
> > > > Hello,
> > > >
> > > > I am learning block device drivers and have a newbie question. Given 
> > > > a block device, is there anyway that I could set its block size? For 
> > > > example, I want to write a block device driver that will work on an 
> > > > existing block device.  In this driver, I want block size smaller. 
> > > > (The idea looks confusing but I could explain if anybody is 
> > > > interested :- )  However,  typically the block size is 1KB, now I 
> > > > want to set it to 512 or 256.  Can I do it?
> > > >
> > > > TIA
> > > > Lei
> > > >
> > > >        
> > >
> > >      
> >
> > --
> > Kernelnewbies: Help each other learn about the Linux kernel.
> > Archive:       http://mail.nl.linux.org/kernelnewbies/
> > FAQ:           http://kernelnewbies.org/faq/
> >    


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