Re: sector size in block device drivers

[nidhi mittal <nidhimittal19@xxxxxxxxx>]

sorry but my question it seems wsnt clear ...
as my ques was 

suppose i have this function 

blk_queue_hardsect_size(

request_queue_t *queue , unsigned short max );

or some other function takes sector as parameter 
there in any of these functions 
how do i decide that whether i should send number sectors in terms of 512 bytes
or in terms of my hardware size 2048 bytes ....

how do i know that in this function communication is between kernel to block layer 
or from block layer to driver 

as in book they just write this 

"All request generated by kernel are multiple of

hardware sect size and properly aligned All the communication 

from block layer and driver is in 512 bytes"

as struct request req i get in request function ....
what should i assume of req->current_nr_sectors are they 512 byte sectors 
or 2048 byte sectors  

pl clarify ....hope i m making sense..

 

On Sun, Feb 1, 2009 at 3:20 PM, nidhi mittal <nidhimittal19@xxxxxxxxx> wrote:

hello

i was writing my initial block device driver following LDD

but was totally confused on KERNEL SECTOR SIZE and hardware sector size issue they discussed in that .

 

they write sth like

if sector number passed between kernel and block layer it should be something and

if its passed between blocklayer and driver it should be something else.

 

means at different place some confusing note abt sector size

can someone clear it to me in simple 2-3 sentences

 

At what places , in which function i shd consider sending sector size with a thought that

at this place it understand sector= 512 bytes

and

At what places , in which function i shd consider sending sector size as my hardware sector size

in thinking that it understand 2048 bytes ...

 

and

most important

in book they write

 

blk_queue_hardsect_size(request_queue_t *queue , unsigned short max );

"All the communication from block layer and driver is in 512 bytes but all request generated by kernel are multiple of 

hardware sect size and properly aligned "

 

so i wanted to know where actually is block layer and where is driver  

where are they separated how do i know when i m going from block layer to driver ....

what i understand is ONLY user space and kernel space

 

it will be very kind if someone clears it to me.

thanks

Nidhi

 

 

Thanks & Regards
Nidhi

-- 
Thanks & Regards 
Nidhi