[PATCH v2 03/20] mmc: support embedded data field in mmc_host

Hi Ohad,

On Mon, Aug 2, 2010 at 5:54 PM, Ohad Ben-Cohen [off-list ref] wrote:

SPI is using these spi_board_info tables to populate the SPI device
trees. These tables are registered early at the board-specific init
code, and are later used by SPI core to populate the devices when the
SPI master controller is registered.

SDIO doesn't normally needs any kind of hard coded data: most devices
are dynamically probed and populated.

On rare cases like the wl1271, we have some platform-specific data we
need to deliver the SDIO function driver (i.e. the irq info in this
case). Since the device is hardwired to a specific controller, it does
make some sense to pass this private data from the controller's info
in the board files, through the host driver, and make it accessible
through the specific host instance that drives this controller.

Btw, if our problem was be broader (e.g., needs to supply private data
for non-hardwired devices), then I agree that a more complex
mechanism, such as the one you suggest, would be needed. But currently
the problem is very simple and the solution is even simpler: just add
1 private pointer to the host.

Hope you find this reasonable,

no, actually I don't. I think this is a hack that intrudes into the
area it completely doesn't belong to.

In fact, one can have 2 views on this problem: either this is a fairly
generic problem we need to address, or this is a very specific corner
case.
Your solution will be treated as a hack in both cases.

If we consider it a generic problem, then we need to find a generic
solution, which is the board_info solution, for instance. FWIW, I2C
also uses this approach now.

If we consider it to be a corner case, let's just add a dummy
platform_device like it's done in WL1251 implementation and keep the
MMC subsystem clean.

Thanks,
   Vitaly