Re: 1024bytes/sect microSD support

[KIYOHARA Takashi <kiyohara%kk.iij4u.or.jp@localhost>]

Hi! Warner,


From: "M. Warner Losh" <imp%bsdimp.com@localhost>
Date: Thu, 26 Nov 2009 08:42:29 -0700 (MST)

> : Also I know, Linux's drivers/mmc/card/block.c always set 512bytes.
> : 
> :   mmc_blk_alloc()
> :   {
> :     :
> :         /*
> :          * Both SD and MMC specifications state (although a bit
> :          * unclearly in the MMC case) that a block size of 512
> :          * bytes must always be supported by the card.
> :          */
> :         md->block_bits = 9;
> :     :
> :   }
> : 
> : 
> : I think that it is necessary to always adjust us to 512 bytes.  If this
> : is not supported, we cannot have Linux and interchangeability.
> : However, I do not know how to set more better it.  Does anyone have an
> : idea?
> 
> FreeBSD always uses 512 byte blocks.  Other block sizes are only
> useful to compute the size of the device, and aren't useful for normal
> operations, nor are they a requirement from a disk I/O sense and I
> don't think they should be visible outside the sd/mmc layer.  I found
> quite a few references to this restriction in the literature when I
> was writing the FreeBSD stack...

I think that it is good that we also always support the size of the
block in 512 bytes.

I will fix this for a while if someone doesn't have more better idea.
(about after two weeks.)  It might bring the influence to the zaurus
user.

Thanks,
--
kiyohara