How to support partitions in driver?

How to support partitions in driver?

[Mukund JB`.]

Dear all,

I have few basic queries regarding my partition implementation in my Sd
driver. 
Sorry for asking such petty things here. But, somehow it's not working &
I am made to ask it here.

I am working on 2.6.10 kernel(x86 architecture).
I have a working SD driver for my multimedia controller.
I have four interfaces for my board.
I call then tfa0, tfa1, tfa2, tfa3 respectively.

I defined then as below...

mknod /dev/tfa0 b 252 0	//device node for first partition of socket 0
mknod /dev/tfa0p1 b 252 1
mknod /dev/tfa0p2 b 252 2
.....
mknod /dev/tfa1 b 252 4	 //device node for first partition of socket 1
....
mknod /dev/tfa2 b 252 8	 //device node for first partition of socket 2
.....
mknod /dev/tfa3 b 252 12 //device node for first partition of socket 3
.....

I implemented the gendisk partition support with the following calls in
the driver.

#define MAX_PARTS 4 // maximum no partitions per device
alloc_disk (4);
gend.first_minor = (SockNo*MAX_PARTS); // SockNo: Current socket card is
// inserted 

Socket 0 & 3 support SD interfaces.
I am able to mount the SD with when inserted in socket 0.
At the same time, I am NOT able to mount the SD when inserted in socket
3. It fails as follows.

mount /dev/tfa3 /mnt 
/dev/tfa3: No such device or address
sfdisk: cannot open /dev/tfa3 for reading.

/proc/Partitions looks ok.
Cat/proc/partitions
252 0 14336 tfa3	// first inserted
252 0 14336 tfa0	 
252 0 14336 tfa2	

The updates to the /proc/partitions are done on and when the card is
inserted into that particular socket.

Can you please update me if I am missing anything that has to be
implemented in the driver apart from the above code?

Why am I not able to mount card in socket 3?

Regards,
Mukund Jampala

Re: How to support partitions in driver?

[Russell King]

On Thu, Aug 18, 2005 at 12:22:55PM +0530, Mukund JB`. wrote:
> I have few basic queries regarding my partition implementation in my Sd
> driver. 
> Sorry for asking such petty things here. But, somehow it's not working &
> I am made to ask it here.

Why don't you use the MMC/SD layer already merged into the kernel
instead of rewriting your own.  Grab a copy of Andrew Morton's
kernel, and look at the code in drivers/mmc and include/linux/mmc.

There are three host drivers there already.  I'm sure you can work
out how to interface the existing framework to your device.

And suddenly you can take advantage of the already existing mmc
block device support, which does support partitions, and does
manage to get hot swapping block devices more or less correct.
(and if it doesn't, it'll be one less driver to fix later.)

-- 
Russell King
 Linux kernel    2.6 ARM Linux   - http://www.arm.linux.org.uk/
 maintainer of:  2.6 Serial core

RE: How to support partitions in driver?

[Mukund JB`.]

Dear Russel,

I have a full-fledged driver working with NO problems. It has been
developed long back.
Now the issue here is to add the partitions support to the existing
driver.

I guess it will involve enough amount of work. If NOT, please provide me
the documentation if available, HOW-TO use the MMC layer.

If the requirement was BIG & bulky what you suggested might have been
apt.
If I can solve it in less effort why go for more effort.
I can always integrate it with main-steam kernel letter. This is the
PEAK time & I am required to submit the patch as soon as possible.

Please understand the reason behind it.

I assure you that I will use the kernel MMC & accomplish what u said
within  next month?
But for now how to implement the partition support in the driver will be
very helpfull.

Thanks & Regards,
Mukund Jampala



>> I have few basic queries regarding my partition implementation in my
Sd
>> driver.
>> Sorry for asking such petty things here. But, somehow it's not
working &
>> I am made to ask it here.
>
>Why don't you use the MMC/SD layer already merged into the kernel
>instead of rewriting your own.  Grab a copy of Andrew Morton's
>kernel, and look at the code in drivers/mmc and include/linux/mmc.
>
>There are three host drivers there already.  I'm sure you can work
>out how to interface the existing framework to your device.
>
>And suddenly you can take advantage of the already existing mmc
>block device support, which does support partitions, and does
>manage to get hot swapping block devices more or less correct.
>(and if it doesn't, it'll be one less driver to fix later.)
>
>--
>Russell King
> Linux kernel    2.6 ARM Linux   - http://www.arm.linux.org.uk/
> maintainer of:  2.6 Serial core

Re: How to support partitions in driver?

[Russell King]

On Thu, Aug 18, 2005 at 01:17:51PM +0530, Mukund JB`. wrote:
> I guess it will involve enough amount of work. If NOT, please provide me
> the documentation if available, HOW-TO use the MMC layer.

I've suggested that you look through the existing three drivers.
There is no how-to written yet, and I don't have time to write one
in the next couple of days before I'm on vacation.

Neither can I teach you how to add partition support to your driver
in these two days.  Again, there's plenty of examples in the kernel,
even in the MMC layer if you really want to re-implement it.

Please try reading some of the already merged code and try to
understand it, as I have already suggested.  Alternatively, please
wait until September.

-- 
Russell King
 Linux kernel    2.6 ARM Linux   - http://www.arm.linux.org.uk/
 maintainer of:  2.6 Serial core