[U-Boot] [PATCH] mmc: add wrappers for MMC block_{read, write, erase}

[Steve Rae <srae@broadcom.com>]

On 14-05-29 11:51 AM, Stephen Warren wrote:
> On 05/29/2014 11:58 AM, Steve Rae wrote:
>> Hi, Stephen
>>
>> On 14-05-29 09:25 AM, Stephen Warren wrote:
>>> On 05/28/2014 04:15 PM, Steve Rae wrote:
>>>> Each wrapper function:
>>>> - switches to the specified physical partition, then
>>>> - performs the original function, and then
>>>> - switches back to the original physical partition
>>>> where the physical partition (aka HW partition) is
>>>>     0=User, 1=Boot1, 2=Boot2, etc.
>>>
>>> This feels wrong; why wouldn't mmc_get_dev() return a block_dev_desc_t
>>> containing block_read/block_write functions that do the HW partition
>>> switching. That way, this is all completely hidden, and all client code
>>> only knows about block devices, rather than having to know about
>>> MMC-specific mmc_block_read/write/erase_hwpart() functions.
>>>
>> This goes back to the initial discussion on this mailing list (which was
>> never resolved):
>>    http://lists.denx.de/pipermail/u-boot/2014-April/178171.html
>> This issue is that the three callback functions defined in
>> 'block_desc_t' do not accept the "partition number" as an argument.
>> It was suggested that we could overwrite those functions; but the
>> "partition number" still needs to be passed in by:
>> (1) overloading the "int dev_num" argument, or
>> (2) adding another argument to the callback functions
>> I assumed that neither of these was acceptable, so I have proposed these
>> wrappers...
>
> Can't the data simply be stored in the block_desc_t itself?
>
If I understand this suggestion, are you proposing:
- add an "unsigned int specified_hw_part" to the block_desc_t

Then the usage would become:
mmc->block_dev.specified_hw_part = 1;	  /* specify Boot1 partition */
mmc->block_dev.block_read(0, 0, 1, buf);  /* read first block (from 
Boot1 partition) */
mmc->block_dev.specified_hw_part = 0;	  /* specify User partition */
mmc->block_dev.block_read(0, 0, 1, buf);  /* read first block (from User 
partition) */

I don't think this is a good idea...
Please clarify!
Thanks, Steve