Re: [U-Boot] MMC: proposal to support multiple physical partitions

29 Apr 2014

      Thanks for the response,
...
-----Original Message-----
From: Pantelis Antoniou [mailto:panto@antoniou-consulting.com]
Sent: Tuesday, April 29, 2014 10:25
To: Steve Rae
Cc: u-boot@lists.denx.de; trini@ti.com; albert.u.boot@aribaud.net
Subject: Re: MMC: proposal to support multiple physical partitions
Hi Steve,
On Apr 24, 2014, at 8:50 PM, Steve Rae wrote:
[... snip ...]
...
...
I have two different proposals:

overload the "int dev_num" argument with encoded  "dev_num" and

"part_num" fields
...

     the dev_num  in the [15:0] bits,

     the part_num in the [30:16] bits,

     a flag to indicate this encoding in [31] bit.

     and modify mmc_bread() to handle this encoded argument, and

implement the above code...
...

create a wrapper function to perform the above code, with an added

argument "int part_num", possibly named:
...

     mmc_block_dev_block_read() -- so that it is similar to the original

calling convention [mmc->block_dev.block_read], or
...

     mmc_pbread() [PartitionBlockRead] -- so that it is similar to the

mmc_bread() [which is the implementation of the callback function]
...
I'd rather go with the wrapper function. Perhaps it's not even needed. The
function called is part of the block_dev (block_read/write etc).
Overwrite those with functions that implemented the switching first, and
then call the original block* function.
The callback function is:
    mmc->block_dev.block_read = mmc_bread
and it accepts four arguments:
    include/part.h: unsigned long   (*block_read)(int dev,
    include/part.h-                               lbaint_t start,
    include/part.h-                               lbaint_t blkcnt,
    include/part.h-                               void *buffer);
Are you suggesting that I should add another argument to this callback?
[...snip...]
...
Regards
-- Pantelis